Citation
Anhydrous ammonia nitrogen for tropical corn, grain sorghum, and bahiagrass sod in multiple cropping minimum tillage systems

Material Information

Title:
Anhydrous ammonia nitrogen for tropical corn, grain sorghum, and bahiagrass sod in multiple cropping minimum tillage systems
Creator:
Baldwin, John Allen, 1947-
Publication Date:
Language:
English
Physical Description:
vii, 246 leaves : ill. ; 28 cm.

Subjects

Subjects / Keywords:
Agronomy thesis Ph. D
Bahia grass -- Fertilizers
Corn -- Fertilizers ( fast )
Dissertations, Academic -- Agronomy -- UF
Multiple cropping ( fast )
Nitrogen fertilizers ( fast )
No-tillage ( fast )
Sorghum -- Fertilizers ( fast )
City of Pensacola ( local )
Corn ( jstor )
Ammonia ( jstor )
Nitrogen ( jstor )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Thesis:
Thesis (Ph. D.)--University of Florida, 1985.
Bibliography:
Includes bibliographical references (leaves 231-245).
Additional Physical Form:
Also available online.
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by John A. Baldwin.

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Source Institution:
University of Florida
Holding Location:
University of Florida
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Resource Identifier:
021919521 ( ALEPH )
13568944 ( OCLC )

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Full Text














ANHYDROUS AMMONIA NITROGEN FOR TROPICAL CORN,
GRAIN SORGHUM, AND BAHIAGRASS SOD IN
MULTIPLE CROPPING MINIMUM TILLAGE SYSTEMS


















BY

JOHN A. BALDWIN



















A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR
THE DEGREE OF DOCTOR OF PHILOSOPHY



UNIVERSITY OF FLORIDA

1985


















ACKNOWLEDGEMENTS


There were many people who contributed to the completion of this

work and deserve special mention. I would like to express my gratitude

to my chairman, Dr. Raymond N. Gallaher, for his contribution to my

education both in and out of the classroom.

My committee members, Dr. Jerry M. Bennett, Dr. Jimmy G. Cheek,

Dr. John E. Moore, and Dr. Roy D. Rhue, also made important contribu-

tions to the completion of this work. A special mention is made to

Dr. W. G. Blue who had to withdraw from my committee due to an assign-

ment in Camaroon, Africa. His guidance and support are sincerely

appreciated.

The on-farm research projects were made possible only through the

efforts and support of the following individuals. Spencer and Peggy

Miller of Miller Crest Farms, Bronson, FL; Danny Stevens and Don

Bennink of North Florida Holsteins, Bell, FL; Bobby Lott, Bronson, FL;

and Frank Quincy, Chiefland, FL.

I thank Mr. J. F. Copeland and his son, Bill, for use of their

anhydrous application equipment.

I would also like to thank the following individuals for their

resources and technical support of this research: Sonny Tomplins,

Shawn Costello, David Block, Bill Carter, Betty Hurst, Evelyn

Bluckhorn, and Anthony Drew, Technical Assistants and Extension workers,

IFAS, Gainesville and Bronson, FL.



ii











I also want to thank the Levy County Commissioners, Sammy Yearty,

Chairman, Donald Holmes, Elmer Smith, J. L. Townsend, and Mike Davis,

for their support and allowing me absence from my position as Levy

County Extension Director when necessary to pursue this degree program.

Lastly, but most importantly, I would like to give a special

thanks to my wife, Marilyn, and sons, Matt and Jason, for their moral

support, willingness to pitch in and help when it was most needed, and

the sacrifices which they made in their personal lives which allowed me

to complete this work.











































iii



















TABLE OF CONTENTS


Page

ACKNOWLEDGEMENTS . . . ... . . ii

ABSTRACT . . . . . . . vi

CHAPTERS

1 LITERATURE REVIEW . . . .. . 1

Introduction . . . . . 1
No-Tillage multicropping Corn and Sorghums in Sods ..... 2
Nitrogen Fertilization of Corn and Sorghum . . 6
Nitrogen Fertilization of Bahiagrass . . ... 10
Dry Matter Accumulation and Mineral Composition of
Corn and Sorghum . . . . . 17

2 ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR
TROPICAL CORN PLANTED INTO BAHIAGRASS SOD BY
MINIMUM TILLAGE METHODS .. . . . .. 25

Introduction . . . . ... . 25
Materials and Methods . . . .... 28
Results and Discussion . . . . ... 34
Conclusions . . . ... . 68

3 ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR
GRAIN SORGHUM PLANTED INTO BAHIAGRASS SOD BY
MINIMUM TILLAGE METHODS . . . . ... 71

Introduction . . . . .. . 71
Materials and Methods ... . . . 73
Results and Discussion . . . . .. 74
Conclusions . . . .. . 107

4 YIELD AND CHEMICAL COMPOSITION OF BAHIAGRASS AS
INFLUENCED BY NITROGEN RATE, SOURCE, AND APPLICA-
TION METHODS . . . . . . 109

Introduction . . . . . .. 109
Materials and Methods . . . . . 111
Results and Discussion . . . . 115
Conclusions . .. . . . 139




iv











Page

5 ACCUMULATION OF DRY MATTER AND NUTRIENT UPTAKE OF
TROPICAL CORN, GRAIN SORGHUM, AND FORAGE SORGHUM . .. .145

Introduction . . . . . 145
Materials and Methods . . . . ... 149
Results and Discussion . . . ... 150
Conclusions . . . . ... . 167

6 SUMMARY AND CONCLUSIONS . . . .. 172

APPENDICES

A ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR TROPICAL
CORN PLANTED INTO BIAHAGRASS SOD BY MINIMUM TILLAGE
METHODS . . . . . . 182

B ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR GRAIN
SORGHUM PLANTED INTO BAHIAGRASS SOD BY MINIMUM TILLAGE
METHODS . . . .. . . 204

C YIELD AND CHEMICAL COMPOSITION OF BAHIAGRASS AS
INFLUENCED BY NITROGEN RATE, SOURCE, AND APPLICATION
METHOD . . . .. . . 226

LITERATURE CITED . . . .. . 231

BIOGRAPHICAL SKETCH . . . .. . 246































V


















Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the Requirements
for the Degree of Doctor of Philosophy


ANHYDROUS AMMONIA NITROGEN FOR TROPICAL CORN,
GRAIN SORGHUM, AND BAHIAGRASS SOD IN
MULTIPLE CROPPING MINIMUM TILLAGE SYSTEMS

By

John A. Baldwin

December 1985

Chairman: Raymond N. Gallaher
Major Department: Agronomy

Nitrogen is the largest and one of the most expensive fertilizer

components used in growing corn (Zea mays L.), sorghum (Sorghum bicolor

L. Moench), and bahiagrass (Paspalum notatum Flugge) in the United

States.

The first study investigated the effect of anhydrous ammonia N on

the yield and chemical composition of tropical corn and grain sorghum

when planted by no-tillage management into bahiagrass sod. The experi-

ments were conducted at three locations and arranged in randomized

complete block designs with six replications at five N rates (0, 56,

112, 168, and 224 kg N ha-1). A second study was conducted to deter-

mine the effect of rates (as stated above) and sources of N on the

yield and chemical composition of bahiagrass forage. Nitrogen rates

were whole plots and sources of N (anhydrous ammonia vs. ammonium

nitrate) were split plots replicated four times.





vi











A third study was conducted to determine the effects of anhydrous

ammonia at one rate (168 kg N ha-) on the dry matter (DM) accumulation

and nutrient concentration and content of tropical corn, grain sorghum,

and forage sorghum.
-l
Tropical corn showed a grain yield increase to 56 kg N ha- at
-l
locations 1 and 3 and to 112 kg N ha- at location 2. The corn grain

to residue ratio, averaged over three locations, increased 280% over

the control due to increased N fertility. Grain, residue, and whole
-i
plant DM yields increased to only 56 kg N ha at two locations which

was probably due to insufficient rainfall during the silking to ear

fill period.

Grain sorghum DM yield for grain and whole plant increased to 56
-l
kg N ha- at two locations. Grains and whole plant DM yield increased

to 112 kg N ha- at location three. Insufficient rainfall and

distribution of rainfall affected corn yields more than sorghum yields.

When anhydrous ammonia was compared to ammonium nitrate as sources

of N for bahiagrass, no differences in DM yield were found. Nitrogen,

in.vitro organic matter digestibility (IVOMD), and P concentrations

increased with increased rates of N and were greater when ammonium

nitrate was used as the source of N. The concentration of all

nutrients studied responded to all rates of N.

Dry matter accumulation and nutrient content of tropical grain

sorghum, and forage sorghum increased rapidly following early

vegetative growth. Nitrogen, P, K, Ca, Mg, Fe, Mn, Cu, and Zn concen-

trations increased rapidly during early vegetative growth and decreased

rapidly thereafter.




vii


















CHAPTER 1
LITERATURE REVIEW


Introduction


Vast areas of the southeastern United States are occupied by

perennial grass sods which could be more fully utilized if interplant

multicropping minimum tillage systems were feasible. Also, there are

more than 16 million acres of Entisol and Ultisol soil types which make

up a major portion of the ridge throughout south, central, and north

Florida. These soils may produce different growth habits in corn,

sorghum, and forage growth which needs to be researched. Florida is a

grain deficient state, and utilization of existing sods for interplant-

ing grains would allow more efficient utilization of capital, time,

labor, and resources. Producers throughout the state are currently

facing depressed prices for field crops and livestock, which makes the

need for sound management decisions and best utilization of resources a

necessity to continue in the risky business called "farming." Costs

for establishing bahiagrass (Paspalum notatum L. Flugge) sod have

increased as have costs for producing other commodities. The value of

this forage crop in rotations with other crops is well established, and

the ability to interplant corn (Zea mays L.) or grain sorghum (Sorghum

bicolor L. Moench) into this sod while maintaining the sod for fall

regrowth would be desirable. Throughout most of Florida, bahiagrass is

the predominant improved forage for grazing by cattle. This pasture



1











grass is easily maintained and provides beef cattle producers with an

acceptable forage for grazing during late spring, summer, and early

fall. The productivity and quality of bahiagrass can be improved by

proper application of N fertilizer. However, with low beef prices and

increased cost for N fertilizer, much of this pasture is never

fertilized adequately fr good forage quality and productivity. With

anhydrous ammonia being one of the least expensive sources of N, this

fertilizer material might lend itself to use in interplant cropping

systems in sod or for use as the main source of N for bahiagrass

pasture fertilization.


No-Tillage Multicropping Corn and Sorghums in Sods


No-tillage and other forms of minimum tillage have gained popu-

larity rapidly during the past decade, especially in the midwestern and

southeastwern United States. Compared to conventional tillage systems,

no-tillage and other types of minimum tillage can offer several

advantages, including increased soil moisture availability (Blevins

et al., 1971; Gallaher, 1977), reduced soil erosion loss (Langdale and

Leonard, 1982), less planting delays, and fuel savings (Robertson and

Prine, 1978). In addition, no-tillage practices allow growers to

utilize crop residues and mulches more effectively for soil improvement

and crop protection. Probably the major contributing factors to yield

response from the use of mulch are increased water infiltration and

reduced losses from water runoff (Langdale and Leonard, 1982). By

covering the exposed soil surface, mulches reduce water loss from

evaporation as well as reduce erosion losses due to wind and water.

Mulches may also be used as a soil amendment by increasing water







3


holding capacity and providing new cation exchange sites for improved

nutrient retention. Many multicropping farmers are increasing their

chances for success by utilizing no-tillage or no-tillage plus subsoil-

ing to plant one or more crops in their multicropping system (Gallaher,

1980). Multicropping no-tillage farming requires a high level of

management that most producers have not experienced (Gallaher, 1980).

No-tillage has numerous advantages over conventional tillage planting

management. No-tillage reduces erosion (Moldenhauer and Amemiya,

1969). No-tillage conserves soil moisture when plantings are into a

chemically controlled mulch crop and indications are that a more

vigorous root system develops to aid in withstanding drought stress

(Gallaher, 1977). Moisture availability to plant roots throughout the

growing season is one of the most critical factors limiting crop yields.

Crop water stress is influenced by the total water available to the

plant, stage of growth of the plant, and the rate of evapotranspiration.

The magnitude of crop yield reduction is directly dependent upon the

duration and severity of water stress.

According to Gallaher (1978), mulch tillage is one system used to

help conserve soil moisture and includes leaving residues from previous

crops or utilizing chemically supressed sods on the soil surface in

which to plant crops by no-tillage or other minimum tillage methods

(Adams et al., 1973, 1970; Bennett et al., 1976; Blevins et al., 1971;

Fink and Wesley, 1974; Griffith et al., 1973; Jones et al., 1969;

Moschler et al., 1973; Shear and Moschler, 1969). Properly utilized

mulch can result in significant increases in yields of corn (Blevins

et al., 1971; Gallaher, 1977; Jones et al., 1969; Moody et al., 1963;

Shanholtz and Lillard, 1969). Mulch material also reduces loss of







4


water from the soil by evaporation (Jones et al., 1969; Moody et al.,

1963; Shanholtz and Lillard, 1969). In a Georgia study, no-tillage of

corn using a rye (Secale cereale L.) crop as mulch as opposed to

removal for hay resulted in 3260 kg ha-1 more corn or a 46% increase

in yield. Conservation and better utilization of moisture was the

attributing factor to better yields from the rye mulch (Gallaher, 1977).

Nelson et al. (1977a, b) in no-tillage plantings of corn or grain sorghum

following wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.)

found that no-tillage corn and grain sorghum produced higher yields

when early planted (after small grain for forage) than when planted

late (after small grain for grain). Small increases observed for

irrigated early-planted no-tillage corn and grain sorghum were

attributed to a higher soil water content on non-irrigated no-tillage

crops. Gerik and Morrison (1984) found no differences in yield between

no-tillage and conventional planted grain sorghum following wheat, and

there were trends toward better soil water content under the no-tillage

throughout sorghum development each year of the study. A Virginia

study showed that mulched treatments, whether of undisturbed killed

orchardgrass (Dactylis glomerata L.) sod on no-tillage plots or of

wheat straw on conventional plots, gave the lowest water runoff and

highest soil water content and yield of corn (Jones et al., 1969).
-l
Another Virginia study showed a 1440 kg ha1 yield increase of corn

from no-tillage in orchardgrass sod versus conventional tillage. This

was attributed to less water runoff, less evaporation, and negiligible

erosion (Shanholtz and Lillard, 1969). Elkins et al. (1979) no-tillage

planted corn into tall fescue (Festuca arundinacea Schreb.) and found

that it was possible to obtain good corn yields while maintaining at











least 50% of the grass sod with little or no erosion observed. This

method offers the potential for a combination of corn production and

grazing on erosive land. According to Gallaher (1980) several reports

have been published in Florida on minimum tillage of crops in grass sod

(Lundy et al., 1974; Prine, 1967; Robertson et al., 1964; Prine and

Robertson, 1968; Robertson et al., 1976). None of these studies

involved the use of no-tillage in-row subsoil planting. Three studies

have been conducted utilizing in-row subsoiling when corn or sorghum

was no-tillage planted into bahiagrass sod, but none of these studies

utilized anhydrous ammonia as a source of N (Gallaher, 1978; Robertson

et al., 1980; Stanley and Gallaher, 1980). Gallaher (1978) reported

that grain sorghum tended to yield about the same for no-tillage versus

conventional tillage in a bahiagrass sod. Bahiagrass was effectively

controlled by preapplication of glyphosate (isopropylamine salt of

N-(phosphonometryl) glycine) (Roundup) and post direct application of

Paraquat (l,l'-Dimethyl-4,4'-bipyridinum ion) in this study. Robertson

et al. (1980), using subsoil planting into bahiagrass sod, found there

was a large response to subsoiling for both the no-tillage and conven-

tional method of tillage, but a greater response with no-tillage. The

yield responses, over tillage methods, for subsoiling were related to

stand. Stands (plants ha-1) were improved by subsoiling but more so

for no-tillage than conventional. Forage yields correlated with grain

yields but bahiagrass regrowth yields at harvest were better when corn

yields were low. This suggests that the better groundcover of the

higher yielding treatments shaded out undergrowth. For the 3 years of

the experiments, grain yields for no-tillage were superior or as good

as the conventional method when narrow rows were used and the soil was







6


subsoiled beneath the row to 35 cm. Stanley and Gallaher (1980), with

early planted corn into bahiagrass sod, reported after 2 years of study

that corn yields of up to 9400 kg ha-1 can be realized with no-tillage

practices on bahiagrass sods; however, these plots were under limited

irrigation management.


Nitrogen Fertilization of Corn and Sorghum


The rapidly increasing cost of crop production is forcing an

interest in practices that reduce or eliminate specific cost variables

normally associated with crop production. Some practices which have

been shown to be beneficial in reducing production costs are reduced

tillage, double cropping, and crop rotations. Other methods used to

cut production costs include reductions in fertilizer usage, plant

populations, and herbicide usage. Excessive reduction in any of these

and similar essential items may reduce crop yield below an economical

level and actually increase rather than decerase production costs

(Touchton, 1980). Anhydrous ammonia is one of the cheapest sources of

N which could be used in no-tillage multicropping systems for corn and

grain sorghum.

Nitrogen fertility is an important factor in obtaining maximum

yields of corn or sorghum (Anderson et al., 1985). The response of

corn to increased N fertility differs considerably. Some experimental

hybrids show increases in protein content and/or grain yield as rates

increase (Kamprath et al., 1973; Warren et al., 1980; Nelson, 1956).

Anderson et al. (1985) reported that prolific (more than one ear per

plant (genotypes maintained a greater N utilization efficiency than the

semiprolific genotypes at all N fertility levels and showed a greater











decrease in N utilization efficiency as N fertilization was increased.

The genetic selection for prolificacy under low N fertility may lead to

identification of genotypes with more efficient N utilization. In a

study to determine the response of grain sorghum and corn to applied N,

Lutrick (1978) found that in general the yield of grain sorghum and
-l
corn did not increase significantly when more than 75 kg N ha- was

applied on a yearly basis. The protein concentration increased in the

grain of sorghum and corn for increments of N up to and including 112

kg N ha- Perry and Olson (1975), studying the effect of N fertiliza-

tion on yield and quality of corn and sorghum residues, observed that

grain N concentration increased with N fertilization in both crops.

Grain sorghum N concentration was generally equal to or greater than

corn. Residue yields of both crops were increased significantly by

90 kg N ha- with no further increase at the higher N rate. Corn

grain/stover ratios increased with increasing N levels. Crude protein

of grain sorghum residues was consistently higher than corn while

in vitro organic matter digestibility (IVOMD) values were consistently

lower in grain sorghum. Crude protein increased significantly in grain

sorghum residue with each increasing N level while little increase

occurred in corn. Perry and Olson (1975) observed that corn dry matter

(DM) yields declined as much as 30% within 100 days of harvest. Any

decline in crude protein and digestibility following grain harvest of

corn and grain sorghum appears to be associated with environmental

factors.

Touchton (1980) and Touchton and Hargrove (1982) stated that some

of the cheaper N fertilizers are more susceptible to losses through

ammonia volatilization than the more expensive ones. These losses are







8


often accelerated with surface applications in no-tillage systems.

Climatic and soil conditions that determine the potential for ammonia

volatilization are numerous and whether or not losses will occur in any

particular system are difficult to predict. Mengel et al. (1982) found

that injecting NH3 or urea ammonium nitrate (UAN) below the surface

resulted in consistently higher corn grain yields than applying UAN,

NH NO3 or urea directly on the soil-residue surface. Nitrogen concen-

tration in the leaf and grain also reflected an increase in N use

efficiency with subsurface N placement. Percent N in leaf was signifi-

cantly higher where NH3 or UAN were injected as compared to UAN or urea

surface applied. Eckert (1981) stated that research has shown little

if any differences in corn yield as a result of using different N

sources in conventional tillage production systems. However, the same

was not true for no-tillage systems due to crop residues which may

intercept much material and hold it above the soil surface until rain-

fall washes it into the profile. Prolonged contact with crop residues

may cause loss of applied N and reduce yield. The extent of N loss

will be affected by the type of N fertilizer, the application method

used, soil surface pH, soil drainage, climate, and the nature of the

crop residue. Eckert (1981) reported that anhydrous ammonia is the

preferred source of N in no-tillage systems. Since this material is

injected into the soil, it does not interact with surface residue and

no problems associated with tillage or residue are normally encountered.

Subsurface N application has less effect on surface pH, making it

easier to maintain a favorable pH for weed control.

Smith (1966) stated that the effect of rate of N application

can be quite variable, depending on the crop under consideration.








9


Because of its ability to utilize large amounts of N, the corn crop is

almost ideally suited for use of ammonia. It is well established that

low rates of ammonia application are not likely to appreciably influ-

ence grain protein content, although yield may be substantially

increased. Colliver and Welch (1970) conducted experiments to study

the effects of preplant anhydrous ammonia on germination and early

growth of corn. Corn was planted directly over and parallel to NH3

bands applied at different rates, depths, and times before planting.

Injurious effects on corn observed with certain NH3 treatments were

reduced stand, stunted early growth, restricted seedling root develop-

ment, and increased occurrence of P deficiency symptoms. Increasing

depth of application was more effective at reducing injury than was

increasing the time interval between application and planting. Injury

was largely prevented when application depth was 25 cm, for all times

and rates of application. Mills et al. (1974) reported that toxicity

may be partially overcome if the soil pH is near neutrality. The

principal factors affecting NH+ losses from soil are soil reaction and

the amount of NH4 N applied, but depth of fertilizer placement, cation

exchange capacity (CEC), base saturation, and soil moisture content

also affect retention and volatilization of NH+ (Mills et al., 1974).

Gomes and Loynachan (1984) stated that the nitrification of ammonium to

nitrate is a stepwise biological oxidation in which NH4 ions are con-

verted to nitrate (NO3), mainly by the bacteria of the genus Nitro-

somonas, and NO2 is further oxidized to NO3 by Nitrobacter. The end

product of nitrification (NO3) is not strongly attached to the soil's

cation exchange sites and, thus, is subject to leaching losses by

percolating water. Fenn and Kissel (1976) reported that an increasing







10


CEC resulted in decreasing NH4 losses. Increased depth of incorpora-

tion resulted in reduced NH4 losses. Also, decreasing the soil water

increased the effectiveness of soil incorporation for reducing NH4

losses. Boswell (1977) stated that the agronomic efficiency of

anhydrous ammonia is reported to be equal to other N sources, inferior

in some studies, and superior to the conventional N fertilizers under

some conditions. Various workers recognized that different soil types,

as well as application depth, play a major role in predicting ammonia

sorption. In addition, moisture content, tilth, pH, distribution as

influenced by applicator spacings, and temperature have been shown to

influence the availability of N from anhydrous ammonia.


Nitrogen Fertilization of Bahiagrass


There are 5 million acres of improved bahiagrass pasture in the

southeastern United States. This pasture grass is easily maintained

and provides beef cattle producers with an acceptable forage for cattle

to graze during late spring, summer, and early fall. The yield and

quality of bahiagrass can be improved by proper application of N

fertilizer (Beaty et al., 1960, 1977; Blue, 1966, 1972, 1974; Stanley

et al., 1977). However, with low beef prices and increased cost for N

fertilizer, much of this pasture is never fertilized adequately for

good forage quality and productivity.

Nitrogen is the largest and one of the most expensive components

of bahiagrass fertilization. While anhydrous ammonia is one of the

least expensive sources of available N, research in the 1950's con-

ducted by Blue and Eno (1954) and Blue (1984) indicated that a loss of

up to 40% of applied N could occur due to volatilization of ammonia.










This loss was dependent upon the cation exchange capacity of the soil,

soil temperature, moisture, pH of the soil, and spacing of injectors.

Since the 1950's, new and improved application equipment is in use that

may make the utilization of anhydrous ammonia more economical than

other sources of N. The cost of N from ammonium nitrate (34% N) is 2.4

times that of anhydrous ammonia (82% N). Many studies have been con-

ducted concerning the use of various N rates and sources for fertiliza-

tion of bahiagrass and other tropical forages (Beaty et al., 1960, 1963,

1977, 1980; Blue, 1972, 1974, 1977). Follett and Wilkinson (1985)

reported that effectiveness of N sources varies with placement, soil,

and environmental conditions. Ammonium nitrate often has the highest

+
recovery efficiency. Losses of NH can occur from surface-applied

urea, resulting in a lower efficiency of N use. Anhydrous ammonia

fertilizers are usually the lowest priced per unit of N and have low

loss rates if properly injected into the soil (Follett and Wilkinson,

1985).

Nitrogen is the main limiting nutrient in many forage systems; as

a consequence, large yield increases are obtainable with N fertilization

(Dougherty and Rhykerd, 1985). When N is applied to grasses, the higher

crop growth rates achieved are most often attributable to increased leaf

area indices (LAI). Nitrogen-fertilized grasses have larger cells with

thinner cell walls and, as a consequence, have larger leaves. Nitrogen

also stimulates meristematic activity; which is often reflected in

increased tillering. Leaf senescence is also retarded by N fertiliza-

tion which helps to maintain the photosynthetically active surface

(Dougherty and Rhykerd, 1985).







12


Beaty et al. (1980), in a study of N rates on bahiagrass yields,

reported that forage production efficiency of applied N (kg DM produced

kg- N applied) decreased from 54.6 for the first 84 kg N ha- to 34.0

for the additional N from 84 to 168 kg N ha-1 and further to 5.2 for N

from 168 to 336 kg N ha-1. They stated that with unfertilized bahia-

grass, N should be applied by or before early March, but after the

first year, time of N application makes no practical difference in

yield. At low N rates, harvesting to a stubble height of 3 cm or

less will significantly increase the amount of forage utilized and

harvested. It was concluded that close grazing or clipping of

'Pensacola' bahiagrass (1) increases digestibility by keeping the

forage green; (2) increases the effective yield of a pasture; and

(3) may provide better forage distribution over a season without

affecting yield when split applications of N are made. Most bahiagrass

forage is produced by vegetative tillers which terminate in stolons and

bear their meristems, including the leaf growing points, at the soil

surface. Leaf production is continuous during the summer (Beaty

et al., 1977) and the stolons may be utilized as a feedstuff for beef

cattle (Rodriquez et al., 1973). Some tillers develop flowering culms

which account for a substantial portion of the July to August growth,

but for only a small amount of the total season's forage. Forage pro-

duction of 'Pensacola' bahiagrass as affected by N rates at a clipping

height of 6 to 7 cm has been established and subsequent studies by

Stanley et al. (1977) using clipping heights from 0 to 15 cm showed

forage yields were negatively related to height of clipping.

Tropical grasses have been reported to grow better than temperate

grasses at low N levels. One reason may be that temperate grasses have







13


a higher proportion of roots, thereby reducing the amount of N avail-

able for top growth (Wilson and Haydock, 1971). Another reason may be

that tropical grasses generally have lower N concentrations, partly

because of higher proportions of stem and sheath tissue (Mott, 1974).

Usually 50-80% of N applied to forage grasses is recovered in the

harvested DM (Lazenby, 1983). Recovery may exceed 100% if fertilizer N

increases the availability of soil N. Recovery is dependent on rate

and time of application, source of N, soil N availability, species,

temperature, moisture, and the interval between application and harvest

(Dougherty and Rhykerd, 1985).

Limited information is available on the response of bahiagrass to

anhydrous ammonia as a fertilizer source of N. The efficiency of using

anhydrous ammonia in comparison to other sources of N on various crops

has been studied by many investigators (Smith, 1966). Tucker and Crowe

(1966) summarized the results of many investigations testing the effec-

tiveness of various sources of N on several crops in comparison to

anhydrous ammonia. They concluded that anhydrous ammonia was equal to

most other N sources. The results of most experiments on forage

indicate that, during the year of application, yields are somewhat

higher from grasses fertilized with ammonium nitrate in split applica-

tions than with anhydrous ammonia applied in one application at rates

of 112 to 324 kg N ha-1 (Tesar, 1974). Burton and Jackson (1962)

conducted trials on 'Coastal' Bermudagrass (Cynodon dactylon L.) for 5

years utilizing anhydrous ammonia as one source of N. The anhydrous

ammonia was applied in 40 cm rows with a chizel-type knife. Total

yields were greater for ammonia nitrate fertilized grass at the 112 and

224 kg rates of N when fertilizer was applied in split applications.







14


When the fertilizer was applied in one application in mid-March,

anhydrous ammonia was equal to ammonium nitrate in effectiveness. Hill

and Tucker (1968) found yields equal for all sources and all clippings

at lower rates of N application. At higher rates of N application,

anhydrous ammonia produced lower yields in the first clipping and

higher yields in succeeding clippings. This lag in response was

attributed to sod burn from escaping ammonia. Reducing the applicator

knife spacing tended to increase NH3 retention, decrease sod burn, and

increase the NH3 efficiency at the high rates of N application. Newer

and more effective application equipment may be the cause of the

increased application efficiency. Lechtenberg et al. (1974), using

anhydrous ammonia to fertilize smooth bromegrass (Bromus inermis

Leyss.), found that it was as effective in increasing animal production

per hectare as was ammonium nitrate at the same application rate.

Increasing the N fertilizer for tropical forages has been shown to

increase DM yield and crude protein content. However, more diverse

information is available on the effect of N rate and environmental

factors on the digestibility of tropical grasses. Moore et al. (1970)

reported that 'Pensacola' bahiagrass hays of varying maturities

differed in crude protein content from 10.5 to 7.6% after 2, 4, and 6

weeks of growth and from 7.0 to 5.2% after 10 or more weeks of growth.

In vitro organic matter digestibility (IVOMD) varried from 63.0 to

60.7% after 2, 4, or 6 weeks of growth and from 53.3 to 46.0% after 10

or more weeks growth. They concluded that 'Pensacola' bahiagrass has a

potentially good quality in terms of voluntary intake and nutrient

digestibility. However, quality did decline quite rapidly between 6

and 10 weeks of growth. Low crude protein content may be the primary







15


factor limiting quality at the 10-week growth stage while low nutrient

digestibility may be the primary limiting factor at later stages of

maturity. Van Soest (1985) also reported that most forages decline in

nutritive quality with age. He stated that age and physiological

maturity are not identical. Thus, factors such as cool temperatures

and light that retard maturity promote higher quality at a given age.

Most date-of-cutting studies represent first cuttings taken during

the spring and early summer, when the effects of the warming season and

maturity positively interact. Such studies show steep declines in

digestibility and protein and increases in fiber, lignin, and other

cell wall components. Date-of-cutting information is less useful in

evaluating second cuttings or aftermaths grown in July through

September. At this time, environmental temperature is maximum and no

longer increasing, and digestibilities are not as high in immature

material as they were in the spring. As temperatures decline in the

fall, nutritive value may actually increase with the age of the plant

(Van Soest, 1982). The tropical environment differs in that there is

generally a much higher solar intensity, which, in combination with

adequate moisture and high temperature, means extremely rapid plant

development and growth toward maturity.

Van Soest (1985) stated that crude protein content as influenced

by fertilizer N is the most important effect of fertilization. He also

stated that digestibility is affected relatively little, although

palatability may be. Wilson (1973) indicated that increasing the N

supply from low to moderate levels increased digestibility by 3-5% and

caused a small increase in total soluble carbohydrates in pangolagrass

(Panicum maximum var. trichoglume). Many investigators (Burton et al.,







16


1963; Doss et al., 1966) have demonstrated that DM yield and crude

protein concentration and content of bermudagrass can be increased with

increasing levels of N fertilizer. The effect of N fertilization on

digestibility has not been demonstrated as frequently. Meredith (1963)

reviewed 22 papers where high and low levels of N had been used on a

number of species, including bermudagrass, and concluded that less than

a 1% increase in digestibility was due, on the average, to higher rate

of N. Fribourg et al. (1971), using 'Midland' bermudagrass, found the

average digestible DM increase to be from about 37 to 46% over the

range of applied N. The greatest increase occurred as the N rate was

increased from 133 to 400 kg N ha-1

Henderson and Robinson (1982a) stated that in the southeastern

United States the climate during the growing season of summer perennial

grasses is characterized by considerable fluctuations in temperature,

solar radiation, and rainfall. These climatic fluctuations have been

associated with seasonal variations in yield and forage quality of the

warm-season grasses (Henderson and Robinson, 1982a). Growth rates of

most tropical grasses increase with temperature to 30 to 35 C and

increase with light intensity to 60,000 lux or higher. Conditions

favoring maximum growth rates have frequently resulted in reduced

forage quality. High temperatures during growth periods have been

related to increased proportions of stem, increased fiber concentra-

tions, decreased water-soluble carbohydrate concentration, and reduced

herbage digestibility of tropical grasses (Henderson and Robinson,

1982a; Wilson and Ford, 1973; Wilson and Minson, 1980; Wilson et al.,

1976). Henderson and Robinson (1982b), in a study of tropical grasses

including 'Pensacola' bahiagrass, found that in all grasses that IVOMD







17


consistently decreased as temperature increased, resulting in maximum

digestibility at the lowest temperature. The effect of light on

digestibility ranged from positive to negative, depending on the grass

and temperature. Maximum digestibilities occurred at the high soil

moisture level after 14 days regrowth. The digestibility of the

'Pensacola' bahiagrass was 3.6 percentage units higher after 14 days

regrowth than after 21 days regrowth.


Dry Matter Accumulation and Mineral
Composition of Corn and Sorghum


Increase in dry weight is a useful definition of growth for those

interested in crop productivity. Knowledge of DM production and of

nutrient uptake and distribution is needed to relate to plant growth

and development (Jacques et al., 1975). Crop growth is usually more

accurately characterized by measurement of dry weight than measurement

of fresh weight, which can be strongly influenced by prevailing mois-

ture conditions.

Dry weight increase has been described mathematically as a

function of physiological, phenological, and environmental factors.

Increase in dry weight with time is usually characterized by a

sigmoidal curve (Leopold and Kriedemann, 1975), in which three primary

phases are recognized: expansion, linear, and senescence (Richards,

1969). In the expansion phase, the growth rate (increase in dry weight

per unit of time) is initially slow but the rate increases continuously

as more dry weight is added. Accumulation of dry weight is exponential

until self-shading or other conditions prevent the increasing leaf area

from producing a proportionate increase in the weight of the plant







18


(Watson, 1958; Leopold and Kriedemann, 1975; Duncan et al., 1967). The

end of the expansion phase marks the beginning of the linear phase in

which the increase in DM continues at a constant rate. The final,

senescence phase is characterized by a decrease in growth rate as the

crop approaches maturity and begins to senesce (Salisbury and Ross,

1978).

The patterns of growth and DM distribution observed in tropical

maize (Goldsworthy and Colegrove, 1974) suggest that the capacity of

grain sink to accommodate assimilate can limit grain production.

McPherson and Boyer (1977) pointed out that another potentially serious

problem occurs if sink size has been affected by low leaf water

potential. Moss (1962) and Allison and Watson (1966) have shown that

when grain sink is limited, DM that would have passed to the grain,

accumulates in the stem and husk. Anderson et al. (1985) indicated

that source-sink relationships are important in the accumulation and

distribution of N and DM. They found that prolific genotypes of corn

maintained a greater N utilization efficiency than the semi-prolific

genotypes at all N fertility levels and showed a greater decrease in N

utilization efficiency as N fertilization was increased. The prolific

genotypes partitioned a larger proportion of plant N to the grain at

all N fertility levels, apparently by increasing N remobilization.

The semi-prolific genotypes responded to increased N fertility by

increasing the ear number per plant, grain N content, and grain yield.

Some investigators have measured the inorganic nutrient uptake by

corn and sorghums. It has been recognized that amounts of most

nutrients removed by a crop harvested for silage may be much more

than when the same crop is harvested for grain (Hanway, 1966).







19


A considerable range in values can be expected for each element, since

soil drainage and fertility, climatic conditions, plant population,

crop species and genotype, and fertilizer practice can influence crop

content of each element (Fribourg, 1974). Work by Owen and Furr (1967)

showed little difference in the mineral nutrient content of corn and

sorghum, except for K, which can be influenced by fertilization.

Fribourg et al. (1976) reported the results of inorganic nutrient

uptake by corn and sorghums. The amounts contained in the above-ground
-1
plant parts exhibited considerable range: 34 to 222 kg N ha ; 8 to 34

kg P ha-1; 31 to 271 kg K ha-1; 8 to 55 kg Ca ha-1; and 9 to 45 kg Mg

ha- Since the quantities removed are the products of harvested plant

part weights and percent composition, they are influenced not only by

the climatic, edaphic, genotypic, and management considerations, but

also by soil nutrient availability. Sivakumar et al. (1979) suggested

that plant growth is the result of an effective integration of many

factors. Restriction of growth may occur due to the limitation of any

one factor. For example, water deficits in plants generally lead to

reduced leaf water potentials and stomatal closure, as manifested by an

increased leaf resistance to transpiration. The effects of depletion

and replenishment of soil water on transpiration are of specific

importance to water use and its efficiency in crop production. The

relative rates of absorption and transpiration determine a plant's

internal water balance, which directly affects the physiological and

biochemical process of plant growth. It is widely accepted that corn

grain yields are most severely reduced by water stresses which occur

during the silking and tasseling stages of growth. Additional water

stresses which occur later during the grain filling period can further







20


reduce grain yields by reducing the weights of individual seeds.

Vegetative growth has often been considered the period of corn or

sorghum growth which is least sensitive to water stress (Bennett, 1984;

Denmead and Shaw, 1960; Eck, 1984; Jurgens et al., 1978; Sinclair

et al., 1975).

Growth and DM production of grain sorghum have been reported by

several workers. Vanderlip and Reeves (1972), who defined 10 growth

stages of grain sorghum from emergence to physiological maturity,

suggested that by using those stages as standards the timing of sampl-

ing or treating of sorghum could be described accurately in relation to

the morphological or physiological age or status of the plant. They

report that the general pattern of DM accumulation was the same for

different grain sorghum hybrids and that late maturing hybrids tended

to have higher DM at each stage of development than did earlier matur-

ing hybrids.

Jacques et al. (1974), in studies of grain sorghum hybrids, found

that Ca and Mg uptake was rapid in early plant development, and Ca was

generally taken up more rapidly than Mg during vegetative growth. When

vegetative growth had been completed, more than half of the plant's

total Ca and Mg uptake had occurred. Whole plant nutrient concentra-

tions decreased through most of plant growth due to dilution. Zinc and

Cu concentrations did not decrease as much during grain development as

during vegetative growth. Lockman (1972b), reported that soil acidity,

soil fertility, stage of growth, variety, and climatic conditions

affected the mineral composition of grain sorghums. Jacques et al.

(1975) found that 20 to 30 days after emergence sorghum plants began to

grow rapidly; their dry weight increased faster than uptake of







21


nutrients, thus concentrations decreased. Hanway (1962a) found that

differences in soil fertility influenced the amounts of N, P, and K

taken up by corn plants, but did not markedly change the seasonal

pattern of uptake and distribution of these elements in the plants.

The accumulation of N, P, and K in corn and grain sorghum was linear in

relation to DM accumulation (Fribourg et al., 1976; Hanway, 1962b).

Corn and grain sorghum production may be greatly enhanced by

proper fertilization. As fertilization efficiency is highly inter-

active with many soil properties and climatic factors, plant analysis

has been used as a measurement of the soil-plant nutrient environment.

Since nutrient availability as measured by soil testing may or may not

be highly correlated to final crop yields, plant analysis can be used

effectively in conjunction with soil tests to examine both critical

levels of nutrients needed by the crop and the ability of the soil to

supply those amounts. Both of these analyses are necessary to deter-

mine nutrient cycling in multicropping systems and to refine the

fertilizer requirements of a particular system.

Abundant literature exists concerning plant analysis data for corn

although few data are available for grain sorghum. Because of this

imbalance and the observations of early researchers that the two crops

contain similar amounts of most elements, they have often been

discussed together. Lockman (1972a, b) and Bennett (1971), however,

warn that although nutrient concentrations in the crops are similar,

differences increase in later growth stages and corn data should not be

used to evaluate growth sorghum.

Since nutrient elements are not evenly distributed throughout a

plant and fluctuate widely during its growth, it is of great importance







22


to standardize time of sampling and plant part to be sampled. It is

generally recommended that, for diagnostic purposes, corn be sampled by

collecting 12 to 25 ear leaf samples from tasseling to silk initiation,

and grain sorghum be sampled by collecting 15 to 25 samples from the

second leaf from the top of the plant at heading (Jones and Eck, 1973).

Whole plant sampling at physiological maturity is not a good measure of

nutrient sufficiency in a plant but may be used to determine total

plant content to be used in nutrient cycling determinations.

Critical nutrient levels (CNL) have been the object of much

controversy and may be defined in several ways (Tyner, 1946; Ulrich,

1952) but are essentially the concentration of an element below which

yields decrease or deficiency symptoms appear. Because of the numerous

interactions among nutrient elements themselves (Peck et al., 1969) and

other confounding influences such as soil types (Gallaher and Jellum,

1976) and cultivar differences (Lutz et al., 1972), CNL values must be

used with care. Tables 1-1 and 1-2 list ranges of CNL's for corn and

grain sorghum. Values are for the ear leaf at silk for corn and the

third leaf below the panicle at bloom for grain sorghum. Lockman

(1972c) further reported that N and P levels in leaf tissue were both

well correlated with sorghum grain yield but that K levels were more

irregular and not as well correlated. Zinc levels exhibited a curvi-

linear correlation with grain yield, the correlation becoming negative

as yields increased above the 6280 kg ha- In corn, yields and

nutrient concentrations in the leaf may be also highly correlated.

Bennett et al. (1973) noted grain yield increases with increasing N

and P levels in the ear leaf.













Table 1-1. Critical values for nutrient sufficiency ranges for corn and sorghum.


Critical Nutrient sufficiency ranges
values Corn Sorghum
Element for corn Corn Sorghum grain at grain at
for corn Corn Sorghummaturity
ear leaf ear leaf 3rd leaf maturity maturity

dag kg-l
---------------------------------- dag kg1

N 3.00 2.76-3.50 3.30-4.00 1.00-2.50 2.02
P 0.25 0.25-0.40 0.20-0.35 0.20-0.60 0.42
K 1.90 1.71-2.50 1.40-1.70 0.20-0.40 0.37
Ca 0.40 0.21-1.00 0.30-0.60 0.01-0.02 0.01
Mg 0.25 0.21-0.60 0.20-0.50 0.09-0.20 0.17
mg kg-l
----------------------------------- mg kg ------------------

Mn 15 20-150 8-190 5-15 23
Fe 15 21-250 65-100 30-50 45
Zn 15 20- 70 15- 30 --- 200
B 15 20- 70 15- 30 1-10 ---
Cu 5 6- 20 2- 7 1- 5 13
Al --- 200 0-220 -


SOURCES: Critical values for corn ear leaf, Jones (1967);
Nutrient sufficiency range, Lockman (1972c);
Corn grain at maturity, Jones (1967);
Sorghum grain at maturity, determined by Agronomy Research Support Laboratory and
Analytical Research Laboratory of the Soil Science Department, University of
Florida, R. N. Gallaher (personal communication, 1983).
















Table 1-2. Critical values of grain sorghum nutrients


Nutrient Element Deficient Low Sufficiency Range


-1
--g--------------------------- g kg -------------


Nitrogen (N) < 1.75 1.75-2.49 2.50-3.50
Phosphorus (P) < 0.16 0.16-0.24 0.25-0.50
Potassium (K) < 1.25 1.25-1.74 1.75-2,25
Calcium (Ca) < 0.10 0.10-0.29 0.30-0.60
Magnesium (mg) < 0.10 0.10-0.19 0.20-0.40
Sulfur (S) < 0.10 0.10-0.20 0.21-0.50


-l
_-------------------------------- mg kg --------------


Manganese (Mn) < 15.0 15.0-25.0 26.0-150.0
Iron (Fe) < 10.0 10.0-49.0 50.0-250.0
Boron (B) < 2.0 2.0- 5.0 5.0- 40.0
Copper (Cu) < 2.0 2.0- 5.0 5.0- 20.0
Zinc (Zn) < 15.0 15.0-25.0 26.0- 75.0
Molybdenum (Mo)


These data were taken froim a v:riety of sources and, therefore, should not he taken as
absolute values; however, they can be used for general interpretive purposes (Personal
communication, C. Owen Plank, Agronomist, University of Georgia, Athens, GA, 1983).


















CHAPTER 2
ANHYDROUS AMMONIA AS A SOURCE OF
NITROGEN FOR TROPICAL CORN PLANTED INTO
BAHIAGRASS SOD BY MINIMUM TILLAGE METHODS


Introduction


Nitrogen fertilizer is used in large amounts and is the most

expensive input used in growing corn (Zea mays L.) in the United States.

Vast areas of the Southeast are occupied by perennial sods which could

be more fully utilized if interplant multicropping mininum tillage

systems were feasible. Multicropping systems utilizing bahiagrass

(Paspalum notatum L. Flugge) sod followed by temperate corn have been

studied (Gallaher, 1978; Lundy et al., 1974; Prine, 1967; Prine and

Robertson, 1968; Robertson et al., 1976, 1980; Stanley and Gallaher,

1980). However, only a few of these studies involved in-row subsoiling

and none utilized anhydrous ammonia as the sole source of N. As

mentioned, several researchers have investigated reduced or no-tillage

corn production and have shown it to be advantageous over conventional

tillage on land subject to erosion hazards. Robertson et al. (1976)

have cited several factors that contribute to the acceptance of no-

tillage crop production. Highly erosive land can often be utilized for

no-tillage grain production without serious soil losses. Elkins et al.

(1979) showed that planting into sod usually involves the use of a

contact herbicide to chemically kill or suppress the grass sod. They

found in their experiments that it was possible to obtain good corn



25







26


yields while maintaining at least 50% of the grass sod with little or

no erosion observed. This method offers the potential for a combina-

tion of corn production and grazing on erosive land.

Some reduced or no-tillage management for cropping systems leave a

layer of crop residues on the soil surface that can result in increased

soil water content and reduced soil temperatures during the growing

season and can lead to increased N losses through leaching and

denitrification (Thomas et al., 1973; Unger, 1978). The increased N

loss through leaching and denitrification has been attributed to both

increased soil water content and an increased number of large pores

contiguous to the soil surface (Thomas et al., 1973).

Opportunities to incorporate N fertilizers below the residue layer

in reduced tillage systems are limited. Consequently, the most common

methods currently used in no-tillage systems are broadcasting of solid

ammonium nitrate (NH4NO3) or urea or spraying urea-ammonium nitrate

(UAN) solutions on the soil surface immediately before or after

planting. However, significant N losses can occur through ammonia

volatilization when ammonium N sources, particularly urea, are left on

the soil surface and exposed to the atmosphere (Bandel et al., 1980;

Ernst and Massey, 1960; Hargrove et al., 1977; Terman, 1979; Volk,

1959). A number of soil and environmental factors affect the amount

of N lost through ammonia volatilization from surface-applied N

fertilizers. Among these are soil pH, cation exchange capacity (CEC),

soil organic matter (OM) content, amount and type of residue present,

soil moisture content, temperature, humidity, and the N source used

(Fenn and Kissel, 1976; Ernst and Massey, 1960; Terman, 1979). Because

of the large number of interacting factors involved, the actual amount







27


+
of NH4 lost by volatilization is difficult to predict (Bandel et al.,

1980; Fox and Hoffman, 1981; Terman, 1979).

In addition to N losses from the soil-plant system, a significant

portion of the N applied in no-tillage systems can become immobilized

in the decaying residue mulch and, thereby, reduce the amount of N

available to the growing crop (Doran, 1980). Therefore, anhydrous

ammonia could be the preferred source of N in no-tillage systems.

Since this material is injected into the soil, it does not interact

with surface residue and no problems associated with tillage or residue

are normally anticipated. Subsurface N application has less effect on

surface pH, making it easier to obtain a more favorable pH for weed

control (Eckert, 1981). Mengel et al. (1982) found that injecting NH3

or UAN below the surface resulted in consistently higher corn yields

than applying UAN, NH4NO3, or urea directly on the soil-residue surface.

Corn has potential for late season planting and production of a

second crop to increase productivity in the Southeast (Chambliss et al.,

1979, 1980; Gallaher and Horner, 1983; Monson et al., 1980; Widstrom

and Young, 1980). These studies involved tropical corn hybrids. Mid-

to late summer plantings of temperate hybrids developed for different

planting dates and environments experienced numerous pest problems (All

and Gallaher, 1976, 1977; Widstrom and Young, 1980; Young et al.,

1978). No-tillage planting a summer crop such as tropical corn into a

grass sod could help control erosion problems due to wind or water.

Therefore, methods for chemically suppressing late spring and summer

grass growth, but allowing for fall regrowth would be desirable. The

renovation of the pasture sod with in-row subsoiling plus having grass

regrowth and crop residues for livestock to graze in the Fall could







28


dramatically increase the value and profitability of multicropping corn

with bahiagrass sods.

The objective of this study was to determine the effect of

anhydrous ammonia as the sole source of N for tropical corn planted

into bahiagrass sod using minimum tillage methods.


Materials and Methods


Field Procedures


The experiment was conducted at three locations during 1983 and

1984. The experiment was in a randomized complete block design with

six replications (Table 2-1) utilizing Pioneer brand 'X304C' tropical

corn planted into 15-year-old bahiagrass (c.v. 'Pensacola') sods.

Location 1 was planted on June 1, 1983, on a Kershaw fine sand (thermic,

uncoated typic Quartzipsamment) an excessively drained sand and

location 2 was planted on June 23, 1983, on a Chiefland fine sand

(loamy, siliceous, thermic, Arenic Hapludalf). The third location was

planted on May 29, 1984, on an Arredondo fine sand (loamy, siliceous,

hyperthermic grossarenic Paleudult). Locations 1 and 3 were in Levy

County, Florida, latitude 2930' North, longitude 82o40' West.

Location 2 was in Gilchrist County, Florida, latitude 29050' North,

longitude 82040' West.

Ten days prior to planting, an application of 0.84 kg a.i.

glyphosate ha-1 (isopropylamine salt of N-(phosphonomethyl) glycine)

(Roundup) plus 1.9 L of X-77 surfactant of 95 L of water was applied in
-l -l
a spray volume of 26 L ha- at 2.8 kg cm- This was done to suppress

the bahiagrass sod prior to planting.







29









Table 2-1. Statistical analysis model used for tropical corn
data. Randomized complete block design.


Source DF



TOTAL 29 (rT-l)


REPLICATIONS (r) 5 (r-l)


TREATMENTS (T) 4 (T-l)


ERROR 20 (r-l)(T-l)







30


All plots were fertilized with a broadcast application of 80 kg K

ha-, 25 kg S ha-, and 12 kg Mg ha- just prior to planting. Sources

of K, S, and Mg were K2SO4:MgSO4 (K-Mag) and KCl (Muriate of Potash).

The plots were eight rows, 76 cm wide, and 12.2 m in length. The plots

were planted with an in-row subsoil planter with anhydrous tubes

attached to the subsoil shanks. Corn was planted at a population of

62,000 plants ha- No irrigation was provided at any location. An

application of 0.67 kg active ingredient (a.i.) Carbofuran ha-I

(2,3-Dihydro-2, 2-dimethyl-7-benzofuranyl methylcarbamate) (15G

Furadan) was applied in front of the press wheel at planting. Nitrogen

was applied at planting under the row and injected on the subsoil shank

at a 25 cm depth. Nitrogen rates were randomized and replicated six

times at 0, 56, 112, 168, and 224 kg N ha-1

On July 10 at location 3 and on July 26 and 27 at the other two
-i
locations, 0.05 kg a.i. paraquat ha- (1,1'-Dimethyl-4,4'bipyridinium

ion) plus 0.5 L X-77 in 95 L of water was direct sprayed to further

suppress the sod. The plots were harvested on the following dates at

the three locations: September 12, 1983; September 26, 1983; and

September 9, 1984. Two rows 6 m in length were hand harvested from

each plot for yield determination. The samples were weighed and a five

plant subsample taken for dry matter (DM) determination and chemical

analyses. At 40 days post-emergence, five whole plants and five

youngest mature leaves were collected from each plot for chemical

analyses. At corn bloom, five ear leaves were collected from each plot

for chemical analyses. Planting, plant sampling, and harvest dates are

shown in Table 2-2.















Table 2-2. Planting and harvesting dates, and plant sampling dates for tropical corn when no-
tillage planted into bahiagrass sod.


1983 1984
Operation for Corn
Location 1 Location 2 Location 3


------------------- month/day ------------------


1. Planting date 6/23 6/9 5/29

2. Youngest mature leaf 8/2 7/19

3. Whole plant 8/2 7/19

4. Ear leaf at bloom for corn 8/26 8/20

5. Harvest at black layer 9/26 9/12 9/9

6. Soil samples 9/28 9/14 9/12







32


All plants and plant parts were dried in a forced air oven at 70 C

for 48 hours and weighed. Samples were prepared for further laboratory

analysis by grinding in a Wiley mill to pass a 1 mm stainless steel

screen and then stored in air-tight plastic bags.

Soil samples were taken during the experiment after corn harvest.

Soil test results are shown in Appendix Table A-7.


Laboratory Procedures


For all soils, N analysis employed a micro-kjeldahl procedure

(Bremner, 1965) as modified by Gallaher et al. (1976). A 2.0 g sample

was placed in 25 ml digestion tubes to which 3.2 g of catalyst (90%

anhydrous K2SO4, 10% anhydrous CuSO4), 10 ml concentrated H2SO4 and

2 ml 30% H202 were added. Samples were then digested in an aluminum

block digester (Gallaher et al., 1975) for 2.5 hours at 375 C. Upon

cooling, solutions were diluted to 75 ml with deionized water.

Nitrogen concentrations of these prepared solutions were determined

using an AutoAnalyzer.

All soil P, K, Ca, Mg, Fe, Cu, Mn, and Zn analyses were conducted

using procedures recommended by the University of Florida's Soil

Testing Laboratory using a double acid extraction procedure (Mehlich,

1953). Five grams of air-dried soil were extracted with 0.05 N HC1 +

0.025 N H SO4 at a soil:solution ratio of 1 to 4 (W:V) for 5 minutes.

Soil P was then analyzed using colorimetry. Potassium was determined

by atomic emission spectrophotometry. Calcium, Mg, Fe, Cu, Mn, and Zn

were determined by atomic absorption spectrophotometry. Soil pH was

determined using a 2:1 water:soil ratio.







33


Nitrogen analysis of plant material employed the micro-kjeldahl

procedure as modified by Gallaher et al. (1976). A 0.1 g sample was

placed in 75 ml digestion tubes to which two boiling chips, 3.2 g of

catalyst (90% anhydrous K2SO4, 10% anhydrous CuSO4), 10 ml of concen-

trated H2SO and 2 ml of H202 were added. Samples were then digested
2 4 2 2
in an aluminum block digester (Gallaher et al., 1975) for 2.5 hours.

Upon cooling, solutions were diluted to 75 ml with deionized water.

Nitrogen concentration of these solutions were determined on a

Technicon II AutoAnalyzer.

Phosphorus, K, Ca, Mg, Fe, Cu, Mn, and Zn concentrations were

determined by a routine dry ashing mineral analysis procedure as

modified by R. N. Gallaher (personal communication, Agronomy Department,

University of Florida, Gainesville, FL, 1983) in which 1.0 g samples

were placed in 50 ml pyrex beakers and ashed in a muffle furnace at

480 C for a minimum of 4 hours. After cooling, each was treated with

2 ml concentrated HCI and heated to dryness on a hot plate. An addi-

tional 2 ml of concentrated HCI + water was added to the dry beakers

followed by reheating to boiling and then diluting to 100 ml volume

with deionized water. Solutions were analyzed for P using colorimetry

on an AutoAnalyzer. Potassium was determined by atomic emission

spectrophotometry. Calcium, Mg, Fe, Cu, Mn, and Zn were determined by

atomic absorption spectrophotometry. Organic matter was determined as

the loss in weight after ashing the DM samples.

In vitro organic matter digestibility (IVOMD) of plant material

was determined by the Tilley and Terry (1963) two-stage procedure

adapted by Moore and Mott (1974, 1976) and expressed on an OM basis

(Moore et al., 1972; Moore and Mott, 1974, 1976).







34


Statistical Procedures


The statistical analysis included analysis of variance (ANOVA) and

least significant difference (LSD) for all responses and regression

analysis for orthogonal polynomials utilizing contrast statements where

appropriate. The data from individual locations were analyzed sepa-

rately due to an interaction between treatments and locations. Where

ANOVA indicated differences (probability of F = 0.05) LSD's were

employed to compare treatment means. In the cases where there was

response to N fertilization rate, appropriate regression analysis was

conducted. Regression terms were incorporated into the model if judged

significant at the 0.05 level by the F-test or if a higher order term

in the same variable was judged significant.

The ANOVA, LSD, regression analyses, and correlations were

performed at the Northeast Regional Data Center (University of Florida,

Gainesville, FL) using the General Linear Model (GLM) procedure of the

Statistical Analysis System (SAS). Data filing and transformations

were performed on a Tandy Radio Shack TRS-80 Model III or IV (48K or

64K RAM microcomputer).


Results and Discussion


The success of dryland or non-irrigated crop production is

dependent on precipitation during the crop growing season and available

water stored in the soil. Rainfall data for the three experiments con-

ducted during 1983-84 are found in Table 2-3. Droughty conditions were

reflected in grain yields of corn with the most severe stress occurring

during the silking and grain fill periods at location 1. When the data







35






Table 2-3. Rainfall data during 1983-84 at three locations
where tropical corn was planted into bahiagrass
sod.


1983 1984
Date
Location 1 Location 2 Location 3



--------------------mm ---------------


5/15
5/20
5/25 30
5/30 76
6/5
6/10 102 8
6/15 41
6/20 6 8
6/25 23 25 76
6/30 101
7/5 25 84 89
7/10 13
7/15
7/20 102
7/25 20 25 76
7/30 19 18
8/5 33 38
8/10
8/15 18
8/20 76 127 51
8/25
8/30
9/5 127 10
9/10







36


were analyzed, interactions occurred among N rates and locations, so

locations were analyzed separately.

Several reports indicate that source-sink relationships affect the

accumulation of N. Grain, residue, and whole plant DM yield increased
-i
to 56 kg N ha- at locations 1 and 3 which was probably due to insuffi-

cient rainfall during the silking to ear fill period (Table 2-4).

Grain yield decreased with increasing rate of N at location 1 where

rainfall was limited. This physiological response of corn to drought

stress has been reported previously by Shimshi (1969).

Corn grain yield increased at locations 1 and 3 in response to 56

kg N ha-1 and to 112 kg N ha-1 at location 2 (Table 2-4). Grain yields
-l
averaged over the three locations ranged from 250 kg ha at the zero

rate to 2270 kg ha-1 at the 224 kg N ha-1 rate. The corn grain to

residue ratio reacted differently to N rate at each location and

increased to 56, 112, and 168 kg N ha-1 at locations 1, 2, and 3,

respectively. Corn grain to residue ratio averaged over the three
-l
locations showed a 250% increase from 0 to 224 kg N ha-. Anderson

et al. (1985) stated that the response of corn to increase N fertility

differs considerably due to genotype, climatic, and other environmental

conditions. Some hybrids show increases in protein content and/or

grain yield as N rates increase (Kamprath et al., 1973; Nelson, 1956).

Balko and Russell (1980) reported that some corn inbreds showed no

response while others showed linear or quadratic yield responses to

increased fertility.

Dry matter yield for corn residue and whole plant increased up to
-l1
168 kg N ha-1 at location 2 (Table 2-4). The number of ears ha-

increased in response to 56 kg N ha-1 at locations 1 and 2; however,







37


Table 2-4. Tropical corn yield response to rates of anhydrous ammonia.


Location

N Treatment Average
1 2 3



kg N ha -------- Grain yield Mg DM ha------

0 .24 .24 .26 .25
56 1.17 1.48 1.76 1.47
112 1.08 2.69 2.24 2.00
168 1.12 3.25 2.22 2.20
224 .68 3.58 2.54 2.27

LSD 0.05 .42 .86 .58

-l
------------- Residue Mg DM ha-----

0 1.55 1.12 1.18 1.32
56 2.62 2.97 2.82 2.80
112 2.72 3.29 3.50 3.17
168 3.14 4.30 3.46 3.63
224 2.64 4.31 4.23 3.73

LSD 0.05 .75 .98 .82

-i
--------- Whole plant Mg DM ha-

0 1.79 1.35 1.54 1.56
56 3.79 4.45 4.58 4.27
112 3.80 5.97 5.74 5.17
168 4.25 7.54 5.69 5.83
224 3.32 7.88 6.77 5.99

LSD 0.05 1.02 1.57 1.23

---------------- Grain/residue ----------------

0 .15 .19 .24 .19
56 .45 .52 .61 .53
112 .38 .77 .64 .60
168 .36 .82 .68 .62
224 .27 .83 .62 .37

LSD 0.05 .15 .23 .14







38

-i
the number of ears increased to 224 kg N ha at location 3 (Table

2-5). The ear number also decreased with increasing rate of N at

location 1. The decreased ear number would indicate a source-sink

physiological problem as well as more barren plants at this location.
-l
There were no differences in the number of plants ha- at loca-

tions 1 and 2; however, location 3 did show significant differences to
-I
varying rates of N. The number of ears/stalk responded to 56 kg N ha

at all three locations.

The shelling percent of corn grain was similar at locations 1 and

3, but was significantly lower at location 2 and responded to 56 kg N

ha-1

Almost every plant process is affected directly or indirectly by

water deficits. When plants are subjected to water stress there is a

decrease in photosynthesis and cell enlargement. There is also con-

siderable retention of carbohydrates in photosynthetic tissue. Although

translocation proceeds, its rate is reduced. It is generally accepted

that optimized grain filling requires continued DM production and trans-

location of the product to the grain. Hanway (1962a) reported that the

potential yield of corn grain which is produced late in the season is

determined by the leaf area, which is produced early in the season.

However, less than this potential yield of grain will actually be

attained if (a) the net assimilartion rate is decreased by any factor

such as a moisture deficiency later in the season or (b) the leaf area

is prematurely reduced by some factor that results in premature death

of leaves such as a nutrient deficiency or insect, disease, or hail

damage. If no other factor limits yield, one would expect that







39


Table 2-5. Response of tropical corn agronomic variables to rates of
anhydrous ammonia.


Location
N Treatment Average
1 2 3



kg N ha- ------------------- Plants ha-------------

0 44,470 48,420 22,420 38,440
56 39,450 52,290 27,260 39,840
112 39,450 54,150 30,490 41,360
168 37,660 54,870 25,460 39,810
224 39,450 55,230 30,130 41,600
LSD 0.05 NS* NS 4,650

-l
------------------ Ears ha- -

0 13,630 27,970 16,140 18,290
56 30,840 40,890 25,460 32,100
112 29,050 45,900 29,770 34,900
168 28,690 50,930 24,750 35,200
224 25,100 51,290 32,280 36,340

LSD 0.05 9,750 9,540 5,530

------------------ Ears/stalk -------------------

0 0.31 0.58 0.72 0.47
56 0.78 0.78 0.93 0.80
112 0.74 0.85 0.97 0.84
168 0.76 0.93 0.97 0.88
224 0.64 0.93 1.07 0.87
LSD 0.05 0.22 0.25 0.23

---------------- Shelling percent ----------------

0 78 55 72 68
56 76 68 77 74
112 78 72 77 76
168 77 75 77 76
224 70 73 76 73
LSD 0.05 NS 5 NS


NS = Not significant at the 0.05 level of probability.








40


increasing leaf area index (LAI) up to the point where complete inter-

ruption of light occurs should result in increased grain yield.

Moss (1962) and Allison and Watson (1966) have shown that when the

corn grain sink is missing, DM that would have been translocated to the

grain accumulates in the stem and husk. Goldsworthy and Colegrove

(1974) have shown that the presence of more barren plants probably

explains why more dry weight accumulated in the stems of corn plants.

Missing grain sink would also account for the differences in the values

for grain yield during the current study, since barren plants contribute

to DM but not to grain yield.

Jurgens et al. (1978) in a water stress experiment showed that as

grain development progressed, the rate of grain fill began to exceed DM

accumulation, indicating a net redistribution of stored assimilates.

Eck (1984) stated that N fertilizer increases water-use efficiency of N

deficient soils when water is adequate but less is known of the effects

of high rates of N when water is limiting. Bandel et al. (1975) demon-

strated decreased DM yields of corn from N rates in excess of 200 kg N
-I
ha on low water level treatments. Denmead and Shaw (1960) indicated

that moisture stress prior to silking reduced grain yield by 25%,

moisture stress at silking reduced grain yield by 50%, and stress after

silking reduced grain yield by 21%.

Utilizing contrast statements for orthogonal polynomials, stalk DM

yield showed a linear response to N rate at all three locations (Table

2-6). However, grain DM yield, whole plant DM yield, and the grain to

stover ratio showed quadratic responses to N at location 1 but linear

at locations 2 and 3.








41


Table 2-6. Regression of responses of tropical corn on rate of
nitrogen applied as anhydrous ammonia.


Dependent Variable Regression Equation R



Location 1


Grain yield kg ha1 Y = -691 + 1196X 185X2* 0.52
-1
Stalk yield kg ha Y = 1723 + 270X 0.25
Whole pland yield kg ha-1 Y = -378 + 2675X 378X2 0.36
Grain/stover Y = -.09 + .33X .05X2 0.36
N cone. grain dag kg-1 Y = 1.24 + .10X 0.53
N content grain kg ha-1 Y = 11.17 + .19X 0.60
N cone. stalks dag kg-1 Y = .46 + .08X 0.46
N content stalks kg ha-1 Y = 7.6 + 3.5X 0.46
DOM grain kg ha-1 Y = 575 + 5.7X 0.60
IVOMD stalks dag kg-1 Y = 43.8 + 1.86X 0.49
DOM stalks kg ha-1 Y = 733 + 175X 0.37



Location 2


Grain yield kg ha1 Y = -290 + 884X 0.72
Stalk yield kg ha-1 Y = 882 + 771X 0.59
Whole plant yield kg ha-1 Y = 592 + 1616X 0.70
Grain/stover Y = .17 + .15X 0.52
-1
N cone. grain dag kg1 Y = 1.35 + .04X 0.14
N content grain kg ha- Y = -5.2 + 12.7X 0.75
N cone. stalks dag kg-1 NS**
N content stalks kg ha-1 Y = 3.45 + 4.6X 0.62
IVOMD grain dag kg- NS
DOM grain kg ha-i Y = 580 + 10.2X 0.40
IVOMD stalks dag kg-1 Y = 53 8.5X + 1.2X 0.51
DOM stalks kg ha-1 Y = 386 + 302X 0.59







42


Table 2-6. Continued


Dependent Variable Regression Equation R



Location 3

-1
Grain yield kg ha Y = 297 + 502X 0.55
Stalk yield kg ha-1 Y = 1098 + 654X 0.48
-1
Whole plant yield kg ha Y = 1396 + 1156X 0.55
Grain/stover Y = .31 + .08X 0.35
N cone. grain dag kg- Y = .59 + .19X 0.76
N content grain kg ha-1 Y = -2.7 + 8.6X 0.70
N cone. stalks dag kg-1 Y = .'37 + .08X 0.49
N content stalks kg ha-1 Y = .98 + 6.04X 0.66
IVOMD grain dag ha- --
DOM grain kg ha-1
-1
IVOMD stalks dag kg --
DOM stalks kg ha-1



X = Coded N rate; X = 1-5, 1 = 0, 2 = 56, 3 = 112, 4 = 168, and
5 = 224 kg N ha-.
NS = Not significant at the 0.05 level of probability.
NS = Not significant at the 0.05 level of probability.







43


The concentration of N in corn grain increased in response to 112

kg N ha-I at location 2, to 168 kg N ha-1 at location 3, and to 224 kg
-l
N ha- at location 1 (Table 2-7). At location 1 there was an increased

concentration of N as N rate increased. The concentration of P and K

increased in response to 224 kg N ha-1 and 56 kg N ha-1 rates, respec-

tively, at location 2 (Table 2-7). Nitrogen fertilizer did not affect

the concentration of Ca, Mg, Fe, Mn, Cu, or Zn at locations 1 and 3.
-i
However, at location 2, 168 kg N ha fertilizer caused Ca to increase

and the 112 kg N ha-1 rate caused Mg to increase in concentration

(Table 2-7). Since location 2 had a better rainfall distribution, an

increased uptake of nutrients should have occurred providing higher

concentrations of elements in the grain.

The concentration of N in corn stalks increased up to the 224 kg N

ha- rate at location 1 and up to the 168 kg N ha- rate at locations 2

and 3 (Table 2-8). Regression equations for stalk N concentrations

versus rate of N application are given in Table 2-6. Correlations were

low for N concentration in stalks when compared with N rates.

Phosphorus, K, Mg, Fe, or Mn concentrations in stalks were not affected

by rate of N (Table 2-8). Calcium concentration increased in response

to 56 kg N ha- at location 1 and to 168 kg N ha-I at location 3. Zinc

was highest in the control plots and did not respond to N application.

The content of N in corn grain increased in response to 56 kg N

ha- at location 1 and to the 112 kg N ha- rate at locations 2 and 3

(Table 2-9). Rhoads and Stanley (1981) stated that the amount of grain

produced for each kg of N contained in the aerial portion of corn

plants ranges from 30 to 60 kg. In the current study, grain yield per

kg N in the plant ranged from 25 to 44 kg for 0 to 56 kg N ha-I applied.







44


Table 2-7. Response of tropical corn grain nutrient concentration to
rates of anhydrous ammonia.


Location
N Treatment Average
1 2 3



kg N ha- ------------------N dag kg-1


0 1.30 1.40 0.80 1.20
56 1.50 1.30 1.00 1.30
112 1.60 1.50 1.20 1.40
168 1.60 1.50 1.40 1.50
224 1.80 1.50 1.50 1.60

LSD 0.05 0.18 0.13 0.18


--- ---------- P dag kg-1


0 0.22 0.34 0.34 0.30
56 0.30 0.38 0.35 0.34
112 0.30 0.45 0.36 0.37
168 0.29 0.44 0.37 0.37
224 0.25 0.53 0.39 0.39

LSD 0.05 NS 0.08 NS


------------------K dag kg-1 ------------


0 0.38 0.48 0.42 0.43
56 0.39 0.51 0.40 0.43
112 0.44 0.54 0.40 0.46
168 0.46 0.53 0.39 0.46
224 0.41 0.54 0.40 0.45

LSD 0.05 NS 0.03 NS







45



Table 2-7. Continued


Location

N Treatment Average
1 2 3



kg N ha-1 ------------------Ca dag kg-1


0 5 12 7 8
56 5 7 8 7
112 4 13 8 8
168 5 1l 13 11
224 5 12 13 10

LSD 0.05 NS 2 NS


------------------Mg dag kg-1 ----------


0 0.11 0.18 0.11 0.13
56 0.12 0.18 0.11 0.14
112 0.13 0.23 0.13 0.16
168 0.15 0.22 0.13 0.17
224 0.12 0.23 0.13 0.16

LSD 0.05 NS 0.03 NS

-1
----------------- Fe mg ha-1


0 30 47 53 43
56 32 47 43 41
112 30 55 73 53
168 35 63 83 60
224 33 62 68 54

LSD 0.05 NS NS NS







46



Table 2-7. Continued


Location

N Treatment Average
1 2 3



kg N ha-1 ------------------Mn mg ha-1


0 3.0 7.0 5.0 5.0
56 5.0 8.0 6.0 6.0
112 5.0 8.0 7.0 7.0
168 5.0 9.0 7.0 7.0
224 5.0 9.0 7.0 7.0

LSD 0.05 NS NS NS

-l
------------------ Cu mg ha-1 -----------


0 3.0 2.7 1.3 2.0
56 2.0 2.0 1.3 1.8
112 2.0 2.3 1.3 1.9
168 3.0 2.0 1.0 1.9
224 2.7 2.3 1.0 2.0

LSD 0.05 NS NS NS

-1
------------------ Zn mg ha------------


0 22 50 31 34
56 18 59 31 36
112 18 60 31 36
168 19 59 25 34
224 23 57 27 36

LSD 0.05 NS NS NS



NS = Not significant at the 0.05 level of probability.







47


Table 2-8. Response of nutrient concentration in tropical corn stalks
to ratio of anhydrous ammonia.


Location
N Treatment Average
1 2 3



kg N ha-1 ---------------N dag kg-1


0 0.47 0.58 0.48 0.51
56 0.64 0.46 0.50 0.53
112 0.84 0.55 0.56 0.70
168 0.73 0.59 0.76 0.69
224 0.82 0.55 0.74 0.70

LSD 0.05 0.13 0.07 0.15


-l
----------------- P dag kg-1 -----------


0 0.20 0.31 0.24 0.25
56 0.21 0.23 0.18 0.21
112 0.22 0.20 0.14 0.19
168 0.20 0.21 0.15 0.19
224 0.25 0.20 0.18 0.21

LSD 0.05 NS NS 0.03


-l
------------------ K dag kg-1 ----------


0 0.90 1.20 1.00 1.00
56 0.90 1.10 1.10 1.00
112 1.10 1.20 1.10 1.10
168 0.90 1.20 1.10 1.10
224 0.90 1.00 1.00 1.00

LSD 0.05 NS NS NS







48


Table 2-8. Continued


Location

N Treatment Average
1 2 3



kg N ha-1 ----------------- Ca dag kg-1-----


0 0.14 0.19 0.20 0.18
56 0.24 0.17 0.23 0.21
112 0.21 0.20 0.30 0.24
168 0.20 0.22 0.38 0.27
224 0.19 0.19 0.31 0.23

LSD 0.05 0.03 NS 0.07


------------------ Mg dag kg -------------


0 0.26 0.25 0.18 0.23
56 0.30 0.26 0.17 0.24
112 0.30 0.25 0.18 0.24
168 0.28 0.25 0.26 0.24
224 0.26 0.22 0.19 0.22

LSD 0.05 NS NS NS


-------------- Fe mg kg1


0 60 70 70 70
56 60 80 60 70
112 70 70 70 70
168 60 80 70 70
224 80 70 80 70

LSD 0.05 NS NS NS







49


Table 2-8. Continued


Location

N Treatment Average
1 2 3



kg N ha-1 ---------- Mn mg kg-1 ----------


0 20 20 20 20
56 20 30 40 30
112 20 20 40 30
168 20 30 50 30
224 20 30 40 30

LSD 0.05 NS NS NS

-l
------------------ Cu mg kg-1 --


0 3.0 2.8 2.0 2.6
56 3.3 2.8 2.5 2.8
112 4.5 4.0 3.2 3.9
168 3.5 4.0 4.0 3.8
224 3.6 4.3 3.0 3.6

LSD 0.05 NS 0.8 0.7


-------- --- Zn mg kg --1


0 20 50 30 30
56 10 30 20 20
112 10 20 10 20
168 10 20 10 20
224 10 20 10 10

LSD 0.05 3 9 8



NS = Not significant at the 0.05 level of probability.







50


Table 2-9. Response of nutrient content in tropical corn grain to
rates of anhydrous ammonia.


Location
N Treatment Average
1 2 3



kg N ha- -----------------N kg ha-1


0 3 3 2 3
56 17 20 18 18
112 17 4Q 27 28
168 18 49 31 33
224 12 53 38 34

LSD 0.05 6 12 9


-l
------------------ P kg ha ---- -------


0 1.0 1.0 1.0 7.0
56 3.0 6.0 7.0 5.0
112 3.0 12.0 8.0 8.0
168 3.0 14.0 9.0 9.0
224 2.0 19.0 10.0 10.0

LSD 0.05 1.0 4.0 3.0

-1
------------------ K kg ha--------------


0 1.0 1.0 1.0 1.0
56 5.0 8.0 7.0 2.0
112 5.0 14.0 9.0 9.0
168 5.0 17.0 9.0 10.0
224 3.0 19.0 10.0

LSD 0.05 2.0 5.0 3.0







51


Table 2-9. Continued


Location
N Treatment Average

1 2 3



kg N ha-1 ----------------- Ca kg ha-1 -----


0 0.01 0.03 0.02 0.02
56 0.06 0.12 0.14 0.10
112 0.03 0.34 0.17 0.18
168 0.05 0.48 0.30 0.22
224 0.03 0.43 0.35 0.29

LSD 0.05 0.02 0.13 0.16


-1
------------------ Mg kg ha-1


0 0.3 0.4 0.3 0.3
56 1.4 2.8 1.9 2.0
112 1.4 6.2 2.8 3.4
168 1.6 7.0 3.0 3.9
224 0.8 8.3 3.3 4.1

LSD 0.05 0.6 2.1 1.1


-1
----------------- Fe g ha-1 -----------


0 7 1 2 12
56 4 7 8 6
112 3 15 16 11
168 4 20 19 14
224 2 22 18 20

LSD 0.05 1 7 7







52


Table 2-9. Continued


Location
N Treatment Average
1 2 3



kg N ha-1 ----------------- Mn g ha-1


0 0.09 0.1 0.1 0.10
56 0.50 1.0 1.0 0.80
112 0.50 2.0 2.0 1.50
168 0.60 2.0 2.0 1.50
224 0.30 3.0 2.0 1.80

LSD 0.05 0.10 0.6 1.0

-1
------------------ Cu g ha --------


0 0.60 0.06 0.04 0.05
56 0.20 0.30 0.20 0.20
112 0.20 0.60 0.30 0.40
168 0.30 0.70 0.20 0.40
224 0.20 0.80 0.20 0.04

LSD 0.05 0.10 0.10 0.10

-1
----------------- Zn g ha -----


0 0.5 1.0 0.8 3.0
56 2.0 9.0 6.0 6.0
112 2.0 20.0 7.0 10.0
168 2.0 20.0 6.0 9.0
224 1.5 20.0 7.0 10.0

LSD 0.05 0.6 5.0 2.0







53



The N content of corn stalks responded in the same way as for

grain (Table 2-10). Phosphorus content of stalks responded similarly
-i
at all locations and increased with an application of 56 kg N ha-

Potassium, Ca, Mg, and Mn contents all increased in response to the 56
-i
kg N ha rate at locations 2 and 3. At location 1, Ca and Cu contents

increased to rates of 56 and 112 kg N ha-1, respectively. There was no

significant response to N rate of other nutrients at location 1 (Table

2-10). Colliver and Welch (1970) found that P uptake may be restricted

by application of anhydrous ammonia. Fribourg et al. (1976) stated

that the content of N, P, K, Ca, and Mg exhibits considerable

variability. This was not unexpected since soil drainage, fertility,

climatic conditions, and fertilizer practice can influence yield levels

and crop content of each element. Hanway (1962b) reported that the

mineral nutrition of corn plants in the field appears to influence

grain yields mainly by affecting the leaf area produced early in the

season, and the length of time the leaves remain alive and functioning

during grain formation. Yamaguchi (1974) found in a study of tropical

corn that leaves die quickly after silking and the duration from silk-

ing to harvest is short, hence leaf area duration (LAD) is smaller.

The reason for this is unknown, but it seems that high temperature is

one of the important factors since senescence is slow when temperatures

are cooler. Nair and Babu (1975) stated that Zn-P-Fe interactions

occurred in the corn plant. Higher P levels reduced Zn concentration

in the shoots by more than half as compared to roots. The mobility of

Zn and Fe was impeded from root to shoot in their study.

In vitro organic matter digestibility increased only in corn

stalks at locations 1 and 2; however, digestible organic matter (DOM)







54


Table 2-10. Response of nutrient content in tropical corn stalks to
rates of anhydrous ammonia.


Location
N Treatment Average
1 2 3



kg N ha-1 ---- ------- N kg ha-1


0 7 7 6 7
56 17 13 14 15
112 23 18 19 20
168 23 25 19 24
224 22 24 31 26

LSD 0.05 6 6 7

-l
------------------ P kg ha ------------


0 3.0 3.5 3.1 3.2
56 5.4 6.5 4.9 5.6
112 5.7 6.2 4.7 5.5
168 6.2 9.1 5.3 6.8
224 6.4 8.6 7.5 7.5

LSD 0.05 1.8 2.5 1.4

-1
------------------ K kg ha1 ---- -------


0 15 14 13 14
56 25 33 30 29
112 30 39 37 35
168 29 50 36 38
224 24 46 40 37

LSD 0.05 9 13 11







55


Table 2-10. Continued


Location
N Treatment Average
1 2 3



kg N ha- ------------------Ca kg ha-1


0 2.0 2.0 2.6 2.2
56 6.4 4.8 6.4 5.9
112 5.6 6.0 10.4 7.5
168 6.4 9.3 12.4 9.2
224 5.0 7.9 12.6 8.5

LSD 0.05 1.7 2.4 3.2

-1
------------------ Mg kg ha-1


0 4.1 2.8 2.3 3.0
56 7.9 7.4 4.7 6.7
112 8.1 8.1 6.2 7.4
168 8.7 10.9 6.9 8.9
224 6.3 9.4 7.9 7.9

LSD 0.05 NS 2.9 1.6

-1
---------------- Fe g ha-------------------


0 9 8 9 8
56 17 22 17 19
112 19 23 24 22
168 21 33 26 26
224 22 29 32 27

LSD 0.05 NS 9 8







56


Table 2-10. Continued


Location

N Treatment Average
1 2 3



kg N ha-1 ------------------ Mn g ha-------------------


0 3 2 5 3
56 5 7 12 8
112 7 8 15 10
168 7 12 16 11
224 7 11 17 11

LSD 0.05 NS 4 5

-1
----------------- Cu g ha-1 -----------


0 0.4 0.3 0.3 0.3
56 0.9 0.8 0.7 0.8
112 1.2 1.3 1.1 1.2
168 1.1 1.7 1.4 1.4
224 1.0 1.9 1.2 1.4

LSD 0.05 0.1 0.1 0.1


----------------- Zn g ha-1 -----------

0 3 6 4 4
56 2 8 6 5
112 4 8 5 6
168 3 9 5 6
224 3 8 7 6

LSD 0.05 NS 3 3



NS = Not significant at the 0.05 level of probability.







57


content of grain and stalks increased in response to 56 to 168 kg N
-l
ha (Table 2-11). There was a linear increase for DOM in stalks at

both locations and a quadratic increase for IVOMI concentration at

location 2 (Table 2-6). The IVOMD of corn grain was 60% greater than

for stalks when averaged over all locations and rates. This could be
-i
due to a dilution effect since DOM ha was greater in stalks than in

grain. Monson et al. (1980) in comparing tropical corn with temperate

found no difference in whole plant in vitro dry matter digestibility

(IVDMD) at final harvest, 73% vs 72.1%. Correlation coefficients for

yield, agronomic variables, nutrient concentration, and nutrient

content are found in Appendix Tables A-2 through A-19.

Analysis of the youngest mature leaf at 40 days after emergence

indicated that N concentration was increased by application of 56 to

224 kg N ha-1 (Table 2-12). The only other nutrient that was affected
-l
by N fertilizer was Fe which increased to 168 kg N ha When the

whole plant was sampled at 40 days after emergence, there was a change

in plant concentration of N, Ca, Mg, Fe, Mn, and Ca to N rates of 112,
-l
56, 56, 56, 112, and 112 kg N ha 1, respectively (Table 2-13). When

the ear leaf was sampled at the bloom stage of maturity, fertilizer N
-1
only affected OM and IVOMD at 224 and 56 kg N ha respectively, when

averaged over the two locations (Table 2-14). Nitrogen values ranged

from 1.87 to 2.78 dag kg-1 at 40 days post emergence for youngest
-i
mature leaf, 1.61 to 2.78 dag kg- for the whole plant at 40 days, and
-i
1.66 to 2.43 dag kg-1 for the ear leaf at bloom (Tables 2-12 to 2-14).

Critical nutrient levels (CNL) for corn were first established by Tyner

(1946). He proposed CNL levels of 2.9 dag kg-1 N, 0.29 dag kg-1 P, and

1.3 dag kg-1 K for the sixth leaf at silking. Since then many CNL







58


Table 2-11. Response of tropical corn grain and stalk organic matter
to rates of anhydrous ammonia.


Location
Average
N Treatment 1 2

Grain Stalk Grain Stalk Grain Stalk


kg N ha -------------------- OM dag kg -------

0 99.4 96.2 99.0 97.0 99.2 96.6
56 99.5 95.7 98.8 97.2 99.2 96.5
112 99.2 95.7 98.8 96.9 99.0 96.3
168 98.3 95.0 98.8 97.0 98.6 96.0
LSD 0.05 0.5 0.5 NS* NS

-i
--------------------- OM Mg ha -----------

0 0.24 1.49 0.23 1.08 0.23 1.29
56 1.16 2.51 1.46 2.89 1.31 2.70
112 1.07 2.60 2.65 3.19 1.86 2.89
168 1.10 2.98 3.21 4.17 2.15 3.57
224 0.67 2.49 3.53 4.20 1.43 3.35
LSD 0.05 0.42 0.71 0.85 0.96

-l
------------------- IVOMD dag kg-1

0 74.0 45.2 77.9 46.0 76.0 45.6
56 71.8 48.3 76.0 40.8 74.0 44.6
112 74.9 49.5 74.5 38.5 74.7 44.0
168 76.1 50.5 71.6 39.6 76.1 45.1
224 77.6 53.4 70.6 41.5 74.1 47.5
LSD 0.05 NS 3.7 NS 3.4

-1
-------------------- DOM Mg ha-1-----------

0 0.18 0.69 0.14 0.52 0.16 0.61
56 0.84 1.27 0.82 1.20 0.83 1.24
112 0.82 1.34 1.47 1.26 1.15 1.28
168 0.84 1.59 1.85 1.71 1.35 1.65
224 0.51 1.41 1.79 1.77 1.15 1.60
LSD 0.05 0.32 0.36 0.53 0.41


NS = Not significant at the 0.05 level of probability.















Table 2-12. Tissue analysis of corn leaves at 40 days as influenced by nitrogen rate at two locations.


N P K Ca Mg Fe

N
Treatment Location Location Location Location Location Location
Treatment


1 2 1 2 1 2 1 2 1 2 1 2

1 - - - - -
kg ha -------------------------------dag kg ------------------- mg kg -


0 1.89 1.84 0.35 0.23 2.11 2.46 0.19 0.14 0.19 0.15 92 57

56 2.65 2.15 0.24 0.25 1.81 2.49 0.27 0.16 0.23 0.15 122 60

112 2.47 2.75 0.24 0.19 1.68 1.94 0.25 0.20 0.26 0.15 122 72

168 2.51 2.61 0.28 0.20 2.00 1.80 0.23 0.22 0.24 0.16 155 77

224 2.60 2.96 0.26 0.22 1.92 1.93 0.25 0.19 0.27 0.16 147 62

LSD .05 .04 .54 NS NS NS NS NS .04 NS NS 34 10















Table 2-12. Extended


Mn Cu Zn OM IVOMD


N
N Location Location Location Location Location
Treatment


1 2 1 2 1 2 1 2 1 2


g -1 -1 -1 o
kg ha -------------------- mg kg -------------------- ------------ dag kg --- a


0 29.75 31.00 4.75 5.50 25.25 32.75 94.98 96.05 57.53 54.30

56 30.00 29.25 3.75 4.50 17.00 29.75 95.80 96.55 60.20 58.40

112 31.50 35.50 4.25 5.50 16.50 22.50 94.58 97.08 66.75 59.85

168 34.75 28.75 3.75 5.75 16.00 25.00 94.68 96.83 63.63 59.93

224 38.00 33.25 4.25 6.00 15.50 25.00 93.43 96.05 62.58 60.25


LSD .05 NS NS NS NS 6.3 NS NS NS NS NS


NS = Not significant at the 0.05 level of probability.














Table 2-13. Tissue analysis of corn whole plant at 40 days as influenced by nitrogen rate at two
locations.


N P K Ca Mg Fe


N
N Location Location Location Location Location Location
Treatment


1 2 1 2 1 2 1 2 1 2 1 2

1 1 2-

kg ha -------------------------------dag kg-1 -- mg kg-1


0 1.55 1.67 0.24 0.34 1.88 1.70 0.29 0.21 0.26 0.26 70 85

56 1.97 1.69 0.28 0.25 1.74 1.63 0.44 0.39 0.34 0.30 82 100

112 2.25 2.21 0.32 0.24 1.62 1.59 0.46 0.39 0.40 0.28 97 97

168 2.53 2.39 0.34 0.27 1.72 1.58 0.43 0.42 0.39 0.31 100 105

224 2.37 3.34 0.38 0.32 1.74 1.59 0.49 0.39 0.39 0.32 100 110


LSD .05 .30 .31 NS NS .09 NS .06 .08 .08 NS NS 17















Table 2-13. Extended


Mn Cu Zn OM IVOMD

N
Treatment Location Location Location Location Location
Treatment


1 2 1 2 1 2 1 2 1 2


-1- -1
kg ha- --------------------- mg kg1 --------------------------dag kg


0 25 17 4 4 17 20 91.78 96.45 60.53 63.98

56 25 30 4 5 23 17 90.40 96.48 62.08 58.93

112 30 32 6 7 26 18 90.38 96.02 62.35 58.02

168 34 31 6 7 19 18 90.28 95.96 64.93 59.05

224 32 30 6 7 16 19 80.20 95.98 63.98 57.63


LSD .05 NS 10 1 1 NS NS NS .39 NS 3.50


NS = Not significant at the 0.05 level of robability.
NS = Not significant at the 0.05 level of probability.















Table 2-14. Tissue analysis of corn ear leaf at bloom as influenced by nitrogen rate at two locations.


N P K Ca Mg Fe


N
Treatment Location Location Location Location Location Location
Treatment


1 2 1 2 1 2 1 2 1 2 1 2



kg ha -------------------------------dag kg--------------------------------- -- mg kg -


0 1.67 1.65 0.30 0.28 2.87 2.98 0.27 0.23 0.33 0.26 90.0 197.0

56 2.58 1.68 0.38 0.23 2.09 2.98 0.36 0.25 0.29 0.23 227.5 147.0

112 2.67 1.96 0.24 0.20 1.76 2.73 0.38 0.27 0.42 0.25 177.5 132.5

168 2.37 2.06 0.28 0.19 2.65 2.73 0.33 0.27 0.40 0.25 267.5 135.0

224 2.57 2.30 0.26 0.20 2.36 2.29 0.34 0.26 0.40 0.23 157.5 167.5


LSD .05 .32 NS NS NS NS NS NS NS NS NS 30 NS















Table 2-14. Extended


Mn Cu Zn OM IVOMD


N
N Location Location Location Location Location
Treatment


1 2 1 2 12 1 2 1 2


-1 -1 -- ---1--
kg ha-1 -------------------- mg kg ------------ dag kg-1


0 37.25 33.25 5.00 4.50 26.75 36.75 90.70 96.15 60.38 61.73

56 37.50 30.00 4.75 3.25 14.50 34.25 91.70 95.78 69.83 67.70

112 40.50 30.25 4.25 4.50 13.50 25.25 92.78 94.25 69.05 63.65

168 40.00 35.00 4.00 3.75 11.75 25.50 95.18 96.53 69.23 65.40

224 48.00 31.25 4.25 4.25 13.25 25.25 95.18 96.53 69.23 65.40


LSD .05 NS NS NS NS 3 NS 2 1 2 2


NS = Not sinificant at the 0.05 level of bability.
NS = Not significant at the 0.05 level of probability.







65


values or ranges of values have been proposed, but the consensus of the
-l
literature places CNL levels at approximately 2.75 to 3.50 dag kg for

N, 0.25 to 0.40 dag kg- for P, and 1.5 to 2.5 dag kg- for K, when

measured in the ear leaf at silking. In the current study, no rate of

N gave these levels of N in the ear leaf when sampled. Phosphorus

tended to decrease with increasing rate of N, and only the control and
-l
56 kg N ha- would meet CNL requirements for P. Potassium met or

exceeded the CNL requirement (Table 2-14).

Correlation coefficients for nutrient concentration used to

predict grain, stalk, and whole plant DM yields by three sampling

methods are found in Table 2-15. When the youngest mature leaf was

sampled at 40 days post emergence there was a high positive correlation

between N and Ca concentration in the leaf with final grain, stalk, and

whole plant DM yield. Potassium was negatively correlated to grain

yield. Zinc was also negatively correlated but to stalk and whole

plant yield as well as grain yield. Phosphorus, Mg, Fe, Mn, Cu, DM,

OM, and IVOMD were not well correlated with grain, stalk, and whole

plant yield at either locations utilizing this sampling technique.

Calcium and N were well correlated with final yield but neither

nutrient met sufficiency levels in this study. At this stage of growth,

N concentration should range from 3.5 to 5 dag kg-1 and Ca from 0.30-

0.70 dag kg-1. Nitrogen and Ca concentration in the youngest mature

leaf did not meet the above mentioned levels at any rate of applied N

(Table 2-12).

When the whole plant was sampled at 40 days post emergence more

nutrients were correlated with final grain, stalk, and whole plant DM

yields (Table 2-15). Nitrogen and Ca were again positively correlated







66


Table 2-15. Correlation coefficients between plant characteristics and
grain, stalk, and whole plant dry matter yield for
tropical corn at two locations.


Youngest mature Whole plant Ear leaf
leaf at 40 days at 40 days at silking


Location Location Location


1 2 1 2 1 2



dag kg- ---------------------grain kg ha-1

N 0.69 0.64 0.69 0.74 0.71 0.79
P -0.65 NS* NS NS NS NS
K -0.52 -0.47 -0.56 -0.44 NS NS
Ca 0.69 0.42 0.76 0.66 0.54 0.43
Mg 0.57 NS 0.52 0.53 NS NS
Fe NS 0.39 NS NS 0.43 -0.43
Mn NS NS NS NS NS NS
Cu NS NS 0.44 0.68 NS NS
Zn -0.42 -0.56 NS NS -0.61 -0.41
DM NS -0.41 NS -0.46 -0.55 NS
OM NS NS NS -0.39 NS NS
IVOMD NS 0.38 NS -0.53 0.73 NS

-i
--------------------- stalks kg ha -------------

N 0.70 0.57 0.50 0.50 0.57 0.57
P -0.52 NS 0.40 NS NS NS
K NS -0.38 -0.60 -0.40 NS NS
Ca 0.58 0.43 0.77 0.68 0.45 0.48
Mg 0.46 NS 0.67 0.65 NS NS
Fe NS NS 0.39 0.40 0.40 NS
Mn 0.49 NS 0.49 0.39 NS NS
Cu NS NS 0.44 0.47 NS NS
Zn -0.51 -0.50 NS NS -0.62 NS
DM NS -0.47 NS -0.53 -0.66 NS
OM NS NS NS NS 0.38 NS
IVOMD NS 0.43 0.39 -0.65 0.69 0.43








67


Table 2-15. Continued


Youngest mature Whole plant Ear leaf
leaf at 40 days at 40 days at silking


Location Location Location


1 2 1 2 1 2


dag kg- ------------------ whole plant kg ha-I
N 0.73 0.63 0.49 0.65 0.66 0.71
P -0.60 NS NS NS NS NS
K NS -0.45 -0.62 -0.44 NS NS
Ca 0.65 0.45 0.81 0.71 0.45 0.48
Mg 0.53 NS 0.66 0.62 NS NS
Fe NS NS 0.40 NS 0.44 0.40
Mn 0.37 NS 0.38 NS NS NS
Cu NS NS 0.46 0.60 NS NS
Zn -0.50 -0.56 NS NS -0.65 NS
DM NS -0.46 NS -0.52 -0.66 NS
OM NS NS NS NS NS NS
IVOMD NS 0.43 NS 0.62 0.75 0.40



NS = Not significant at the 0.05 level of probability.







68


with grain, stalk, and whole plant DM yields with K being negatively

correlated. However, Cu and Mg were also positively correlated with

final DM yields.

When the ear leaf was sampled at mid-silking, only N, Ca, and Zn

were well correlated at both locations to predict grain yield.

Nitrogen and Ca concentrations in the leaf were positively correlated

while Zn was negatively correlated. Nitrogen, Ca, and IVOMD were

positively correlated to stalk and whole plant DM yield. The reason

for the IVOMD being correlated to yields of stalk and whole plant is

that the IVOMD of grain does not vary much but is directly influenced

by moisture availability, DM accumulation, source-sink, and nutrient

uptake in the vegetative portions of the plant. Bennett et al. (1973)

noted grain yield increases with increasing N and P levels in the ear

leaf. Gallaher et al. (1972) found that in corn, seasonal variation in

rainfall, temperature, and sunlight caused large differences in yield

and ear leaf concentration of K. Hanway (1962c) reported that several

researchers have found high positive correlations between the percent-

ages of N, P, and K in corn leaves at silking time and the yield of

grain.


Conclusions


Grain, residue, and whole plant DM showed a positive response to
-l
the 56 kg N ha- rate at two locations. At the third location, a

significant increase for the yield parameters occurred in response to
-l
the 112 kg N ha rate. There was a 250% increase for the corn grain

to residue ratio over the control. Insufficient rainfall during the

silking through ear fill period decreased grain yields more than







69


residue yields. Also, grain yields were more depressed when the

highest rate of N (224 kg ha-1) was applied at location 1. Grain,

stalk, and whole plant DM yields increased linearly at locations 2 and

3, but increased quadratically at location 1 for grain and whole plant

DM yield due to moisture stress. The concentration of nutrients varied

with N fertilizer rate at each location. Nitrogen content increased

linearly at all locations. Total grain yield per kg of N content

ranged from 25 ro 44 kg ha- The N content of stalks responded the

same as grain. The concentration and content of most other nutrients

did not respond to N rate at any location or only increased in response
-l
to the 56 kg N ha rate.

The analysis of diagnostic samples indicated that N and Fe were

the only elements increased by N rate when youngest mature leaves were

sampled at 40 days post emergence. Whole plant samples at 40 days

exhibited a change in nutrient concentration for N, Ca, Mg, Fe, Mn, and

Cu. Ear leaf sampled at mid-silk showed an increase to N rate for OM

and IVOMD. The concentration of N and P were lower than the CNL values

recommended by Tyner (1946) for sufficiency levels in corn ear leaves.

Only K met the CNL values recommended by various researchers. Nutrient

concentration by three sampling methods as predictors of grain yield

indicate that N, Ca, and Zn were all well correlated with grain, stalk,

and whole plant DM yield when the youngest mature leaf at 40 days was

utilized. When the whole plant at 40 days post emergence was sampled,

N and Ca were positively correlated to final yields with K being

negatively correlated. Copper and Mg were also positively correlated

with final DM yields when this sampling technique was utilized. When

the ear leaf at silking was sampled, N and Ca were positively







70


correlated and Zn negatively correlated with grain yield. Nitrogen,

Ca, and IVOMD were positively correlated to stalk and whole plant DM

yield.


















CHAPTER 3
ANHYDROUS AMMONIA AS A SOURCE OF
NITROGEN FOR GRAIN SORGHUM PLANTED INTO
BAHIAGRASS SOD BY MINIMUM TILLAGE METHODS


Introduction


Grain sorghum (Sorghum bicolor L. Moench) is gaining popularity in

the Southeast as a feed grain. It has been studied in multicropping

systems (Nelson et al., 1977a) and fits well into a combine type farm-

ing operation. Date of planting is not as limiting and yield increase

from close row spacing is greater than from corn (Zea mays L.) or

soybeans (Glycine max L. Merrill) (Larson and Maranville, 1977). Under

some conditions higher grain yields have been produced with grain

sorghum than with corn (Lutrick, 1978). Vast areas in the Southeast

are occupied by perennial sods which could be more fully utilized if

interplant multicropping minimum tillage systems were feasible.

Multicropping systems utilizing bahiagrass (Paspalum notatum L. Flugge)

sod followed by grain sorghum have been studied (Lundy et al., 1974;

Prine and Robertson, 1968; Robertson et al., 1976). However, only a

few of these studies involved in-row subsoiling and none utilized

anhydrous ammonia as the sole source of N.

Grain sorghum has high yield potential (Smith, 1966) and produces

grain which can be increased appreciably in protein content. Magnitude

of grain sorghum response to N fertilizer addition is indicated by

findings of Miller et al. (1964) and Nelson (1952). Grain sorghum



71







72


generally responds to N application similar to corn. However, yield is

not so easily depressed as that of corn when N deficiency exists. The

crop has a tendency to produce appreciable grain of very low protein

content when corn would likely produce a very low yield. Grain sorghum

tends to give less yield increase for a given application of N than

corn which may be due in part to its ability to recover more available

N from the soil. This behavior may be due to its ability when under

stress to delay maturity allowing for more uptake of N from the soil.

The level of N to which grain sorghum will respond varies considerably

with environmental factors, soil type, fertilizer application rate, and

climatic conditions (Lutrick, 1978). Johnson and Cummins (1967)

reported that in Georgia 112 kg N ha-1 applied anytime up to 6 weeks

after planting would give maximum yields of forage sorghum. Valentine

and Onker (1968) observed a yield increase for irrigated grain sorghum

up to 180 kg N ha-1 with the 135 kg N ha-I rate giving the optimum

response. They obtained an 8-year average grain yield increase of 1350

kg ha-1 from the first 45 kg of N, 390 kg grain ha-1 from the second
-i
45 kg N, and225 kg grain ha- from the third 45 kg N. Lutrick (1978)
-l
applied ammonium nitrate at rates of 0 to 188 kg N ha-. In general,

the yield of grain sorghum did not increase significantly when more

than 75 kg N ha-1 was applied on a yearly basis. The protein concentra-

tion increased in the grain of sorghum for increments of N up to and
-i
including 112 kg ha-. He then deduced that the recommended rate of

applied N for grain sorghum should be 112 kg ha-I

No-tillage planting a summer crop such as grain sorghum into a

grass sod could hlep control erosion problems due to wind or water.

Therefore, methods for chemically suppressing late spring and summer







73


grass growth, but allowing for fall regrowth would be desirable. The

renovation of the pasture sod with in-row subsoiling plus having grass

regrowth and crop residues for livestock to graze in the Fall could

dramatically increase the value and profitability of multicropping

sorghum with bahiagrass sods.

The objective of this study was to determine the effect of

anhydrous ammonia as the sole source of N in no-tillage plus subsoil

planted sorghum into bahiagrass sod.


Materials and Methods


All materials and methods for this experiment were identical to

those previously presented in Chapter 2 with only a few differences as

discussed below.

The grain sorghum experiment was conducted at three previously

described locations during 1983 and 1984. The experiment was in a

randomized complete block design with six replications utilizing DeKalb

'DK59' grain sorghum planted into 15-year-old bahiagrass (c.v.

'Pensacola') sods. All sorghum was planted at a population of 124,000

plants ha-1. Two rows 6 m in length were hand harvested from each plot

for yield determination. The samples were weighed and a five plant

subsample taken for dry matter (DM) determination and chemical analyses.

At 40 days post emergence five whole plants and five youngest mature

leaves were collected from each plot to determine diagnostic potential

of plant part sampling and analyses. At sorghum bloom, five leaves,

each positioned three leaves down the stalk from the flag leaf, were

collected from each plot for chemical analyses.







74


All plants and plant parts were dried in a forced air oven at 70 C

for 48 hours and weighed. Samples were prepared for further laboratory

analysis by grinding in a Wiley mill to pass a 1 mm stainless steel

screen and then stored in air-tight plastic bags. Planting dates,

sampling, and harvest dates are listed in Table 3-1.

Soil samples were taken following final harvest. Soil test

results are shown in Appendix Table B-1.


Results and Discussion


Rainfall was limiting during the bloom to grain fill period,

particularly at location 1 during 1983 (Table 3-2). As a result of

interactions between N rate and locations, the data in this study were

analyzed by location. Sivakumar et al. (1978) reported that the major

components of sorghum yield which were significantly affected by

drought in the case of non-irrigated plots were tertiary branches per

secondaries, seed number per panicle, and seed size. The reduction in

these components was 46, 26, and 28%, respectively, in their study.

Their data point out the importance of the availability of a few addi-

tional cm of water to a sorghum crop under water stress and benefits

that should accrue from such water application.
-1
Grain DM yield increased to the 56 kg N ha rate at locations 1

and 2 and to the 112 kg N ha-I rate at location 3 (Table 3-3). Residue
-i
yield increased at all three locations to the 112 kg N ha rate, while
-l
whole plant yield responded positively to the 56 kg N ha- rate at
-l
locations 1 and 3 and to the 112 kg N ha rate at location 2.
-1
Grain/residue, percent grain, and the number of plants ha- varied

at each location and contributed to the variation of DM yields and














Table 3-1. Planting and harvesting dates, and plant sampling dates for corn and grain
sorghum planted into bahiagrass sod.


1983 1984
Operation for Sorghum
Location 1 Location 2 Location 3


------------------- month/day ------------------


1. Planting date 6/23 6/9 5/29

2. Youngest mature leaf 8/2 7/19

3. Whole plant 8/2 7/19

4. Third leaf from flag for sorghum 8/26 8/20

5. Harvest at maturity 9/26 9/12 9/9

6. Soil samples 9/28 9/14 9/12







76






Table 3-2. Rainfall data during 1983-84 at three locations
where grain sorghum was planted into bahiagrass
sod.


1983 1984
Date
Location 1 Location 2 Location 3



-------------------- Mm-----------------------


5/15
5/20
5/25 30
5/30 76
6/5
6/10 102 8
6/15 41
6/20 6 8
6/25 23 25 76
6/30 101
7/5 25 84 89
7/10 13
7/15
7/20 102
7/25 20 25 76
7/30 19 18
8/5 33 38
8/10
8/15 18
8/20 76 127 51
8/25
8/30
9/5 127 10
9/10







77


Table 3-3. Grain sorghum yield response to rates of anhydrous ammonia.


Location

N Treatment Average
1 2 3



kg N ha ------- Grain yield Mg ha- -


0 0.51 0.20 0.51 0.41
56 1.92 0.77 1.87 1.52
112 1.86 1.08 2.83 1.92
168 2.22 1.48 3.14 2.28
224 2.50 1.38 1.88 1.92

LSD 0.05 0.60 0.48 0.62

-i
---------------- Residue Mg ha -------------


0 1.58 2.08 0.69 1.45
56 2.96 4.64 2.14 3.25
112 3.65 5.86 3.02 4.16
168 3.85 5.76 2.99 4.20
224 4.30 6.41 2.32 4.34

LSD 0.05 0.54 1.21 0.52

-1
------------ Whole plant Mg ha-------


0 2.10 2.30 1.20 1.90
56 4.92 5.37 3.97 4.72
112 5.56 6.88 5.83 6.10
168 6.12 7.28 6.14 6.48
224 6.80 7.78 4.18 6.22

LSD 0.05 0.90 1.50 1.00







78


Table 3-3. Continued


Location
N Treatment Average
1 2 3



kg N ha-1 ---------------- Grain/residue -----------------


0 0.32 0.11 0.75 0.39
56 0.64 0.17 0.89 0.57
112 0.51 0.19 0.95 0.55
168 0.58 0,25 1.05 0.63
224 0.60 0.21 0.84 0.55

LSD 0.05 0.18 0.06 NS


----------------Grain dag kg--------------


0 24 9 41 24
56 39 14 47 33
112 34 17 48 33
168 36 20 51 36
224 37 17 45 33

LSD 0.05 10 5 10


------------------Plants ha---------------


0 128,680 88,580 66,350 94,540
56 157,950 93,960 76,030 109,310
112 102,000 96,830 83,030 93,950
168 181,610 97,190 76,390 118,400
224 185,060 106,160 60,610 117,280

LSD 0.05 11,800 5,940 14,990



NS = Not significant at the 0.05 level of probability.







79


interactions among locations and rates of N. Location 2 had severe

sorghum webworm (Celama sorghiella (Riley) (Lepidoptera:Noctuidae))

infestation which contributed to lower grain yields and a lower grain

to residue ratio than at the other two locations.

Nitrogen concentration in sorghum grain ranged from 1.5 to 2.2 dag
-l
kg- when averaged over the three locations (Table 3-4). The response

was to the 112 kg N ha-1 rate at location 1 and to the 224 kg N ha-1

rate at the other two locations.

Phosphorus and Fe showed an increase to N rate at only location 1
-l
which was to the 168 kg N ha-1 (Table 3-4). Potassium, Ca, Mg, Mn, Cu,

and Zn concentrations in grain were not affected by N fertilizer at any

location.

Nitrogen concentration of stalks increased to the 168 kg N ha-1

-1
rate at locations 1 and 3 and to the highest rate of 224 kg N ha-1 at

location 2 (Table 3-5). Phosphorus reacted similarly at all locations

and was highest in the control plots with no N applied. This response

is due to dilution effect as more DM was accumulated at higher N rates.

Also, it has been reported that NH3 may have an inhibitory effect on

the uptake of P. Potassium increased to N fertility only at location 2
-i
which was to 168 kg N ha-. Calcium and Mg stalk concentrations

-1
increased similarly to the 168 kg N ha Copper concentration of

-l
stalks varied and increased to the 224 and 168 kg N ha- rates at

locations 1 and 3, respectively (Table 3-5). Zinc was highest in the

control plots at only one location.

Nutrient interactions in grain sorghum are not well documented but

several studies have investigated particular ratios and interactions.

More than half of the total nutrient uptake in the vegetative growth of







80


Table 3-4. Response of grain sorghum grain nutrient concentration to
rates of anhydrous ammonia.


Location

N Treatment Average
1 2 3



kg N ha-1 --- ----------N dag kg-1


0 1.61 1.68 1.15 1.48
56 1.67 1.52 1.14 1.44
112 1.99 1.7 8 1.34 1.70
168 2.17 1.95 1.53 1.89
224 2.34 2.41 1.90 2.22

LSD 0.05 0.25 0.42 0.17

-1
------------------ P dag kg-1 ----------


0 0.26 0.44 0.40 0.37
56 0.23 0.32 0.37 0.31
112 0.28 0.34 0.42 0.35
168 0.36 0.32 0.47 0.38
224 0.32 0.36 0.40 0.36
*
LSD 0.05 NS 0.10 NS

-1
------------------ K dag kg-1 ----------


0 0.44 0.55 0.48 0.49
56 0.45 0.55 0.42 0.47
112 0.49 0.55 0.47 0.50
168 0.45 0.57 0.50 0.51
224 0.41 0.52 0.40 0.44

LSD 0.05 NS NS NS







81



Table 3-4. Continued


Location

N Treatment Average
1 2 3



kg N ha-1 ------------------Ca dag kg-1


0 0.03 0.06 0.03 0.04
56 0.03 0.05 0.02 0.03
112 0.03 0.06 0.02 0.03
168 0.02 0.05 0.02 0.03
224 0.02 0.05 0.02 0.03

LSD 0.05 NS NS NS

-1
------------------ Mg dag kg-1 ----------


0 0.20 0.30 0.20 0.20
56 0.20 0.30 0.20 0.20
112 0.20 0.30 0.20 0.20
168 0.20 0.30 0.20 0.20
224 0.20 0.30 0.20 0.20

LSD 0.05 NS NS NS


-1
------------------ Fe mg kg------------------

0 44 82 70 65
56 52 80 88 73
112 38 85 122 82
168 72 68 118 86
224 72 83 137 97

LSD 0.05 19 NS NS







82


Table 3-4. Continued


Location

N Treatment Average
1 2 3



kg N ha-1 ---------- Mn mg kg-1


0 17 30 27 25
56 19 29 18 22
112 18 31 20 23
168 29 30 24 27
224 19 36 21 25

LSD 0.05 NS NS NS

-1
------------------ Cu mg kg --------------


0 4.2 6.3 2.8 4.4
56 3.6 5.7 2.7 4.0
112 4.0 7.0 2.8 4.6
168 4.8 7.2 3.3 5.1
224 4.4 6.7 3.0 4.7

LSD 0.05 NS NS NS

-1
----------------- Zn mg kg ------------


0 20 38 28 29
56 18 34 25 26
112 22 37 27 29
168 24 37 28 30
224 20 35 25 27

LSD 0.05 NS NS NS


NS = Not significant at the 0.05 level of probability.







83


Table 3-5. Response of stalk nutrient concentration in grain sorghum
to rates of anhydrous ammonia.


Location
N Treatment Average
1 2 3



kg N ha------------------- N dag kg-1


0 0.57 0.62 0.48 0.56
56 0.50 0.58 0.50 0.53
112 0.83 0.66 0.56 0.68
168 0.86 0.83 0.76 0.82
224 1.01 1.00 0.74 0.92

LSD 0.05 0.14 0.14 0.15


------ --- kg ha-------------P


0 0.28 0.24 0.24 0.25
56 0.21 0.16 0.18 0.18
112 0.30 0.17 0.14 0.20
168 0.22 0.20 0.15 0.18
224 0.19 0.18 0.18 0.18

LSD 0.05 0.04 0.03 0.03


-l
------------------ K kg ha -----------


0 1.28 1.38 1.01 1.22
56 1.23 1.37 1.05 1.22
112 1.43 1.35 1.06 1.28
168 1.30 1.64 1.05 1.33
224 1.40 1.47 0.97 1.28

LSD 0.05 NS 0.12 NS







84


Table 3-5. Continued


Location
N Treatment Average
1 2 3


-i -i
kg N ha-----------------Ca dag kg---------

0 0.14 0.16 0.20 0.17
56 0.18 0.18 0.23 0.20
112 0.18 0.17 0.30 0.22
168 0.20 0.17 0.38 0.25
224 0.19 0.18 0.31 0.23

LSD 0.05 0.02 NS 0.07


------------------Mg dag kg- ----------


0 0.20 0.21 0.18 0.20
56 0.24 0.22 0.17 0.21
112 0.27 0.25 0.18 0.23
168 0.27 0.26 0.20 0.24
224 0.29 0.22 0.19 0.23

LSD 0.05 0.03 0.03 NS


-1
----------------- Fe mg kg ---- ------


0 74 112 72 86
56 84 135 62 94
112 88 118 68 91
168 82 75 73 77
224 102 77 77 85

LSD 0.05 NS NS NS







85


Table 3-5. Continued


Location
N Treatment Average
1 2 3



kg N ha-1 -------------- Mn mg kg-1


0 36 40 34 37
56 42 42 40 41
112 43 38 44 42
168 50 4.0 47 46
224 43 39 40 41

LSD 0.05 NS NS NS


-1
------------------ Cu mg kg ---


0 3.4 3.8 2.0 3.10
56 3.2 3.7 2.5 3.10
112 3.8 4.5 3.2 3.80
168 3.2 4.7 4.0 4.00
224 4.2 4.7 3.0 4.00

LSD 0.05 0.99 NS 0.66


-1
------------------ Zn mg kg -----------


0 18 31 29 26
56 13 27 20 20
112 15 25 14 18
168 16 25 15 19
224 17 25 15 19

LSD 0.05 NS NS 8


NS = Not significant at the 005 level of robability.
NS = Not significant at the 0.05 level of probability.







86


grain sorghum occurs in early growth (Jacques et al., 1975). They

observed that Cu and Zn were translocaLed from vegetative growth to the

panicle as grain developed but that Mn was not.

Nitrogen content of grain varied in response to 56, 112, and 168

kg N ha-1 at locations 1 to 3 (Table 3-6). This response most likely

relates to the source-sink differences among locations and the response

of the plant to moisture stress. Phosphorus and K content also varied
-l
among locations and ranged from 1 to 10 and 2 to 11 kg ha-
-i
respectively, in grain. Grain Ca content increased to the 56 kg N ha
-l
rate at location 1 and to the 112 kg N ha- rate at locations 2 and 3

(Table 3-6). Greater growth rates in response to N fertilizer would

account for increased Ca uptake, particularly where moisture was not
-l
limiting. Magnesium increased in grain to the 168 kg N ha- rate at
-l
locations 1 and 2 but to the 112 kg N ha- rate at location 3. Iron

and Mn uptake in grain were positively affected by a higher rate of N

at location 1. Copper was not affected by N application. Response was

identical for Cu, and Zn content was lower at location 1 than at

locations 2 and 3 which responded similarly (Table 3-6).

Nitrogen content of sorghum stalks was positively affected by N
-l
fertilizer at all three locations up to the 224 kg N ha1 rate (Table

3-7). Phosphorus stalk content showed a significant increase to the
-l
112 kg N ha rate for locations 1 and 2 with no difference due to N

rate at location 3. Potassium, Ca, Mg, Fe, Mn, Cu, and Zn stalk

contents varied at each location and responded differently to increas-

ing rates of N. The stalk content of each of these elements was

affected by applied N (Table 3-7). Percent OM and IVOMD showed a

positive response in stalks to N rate (Table 3-8). However, total OM







87


Table 3-6. Response of grain nutrient content of grain sorghum to
rates of anhydrous ammonia.


Location
N Treatment Average
1 2 3



kg N ha- ------------------ N kg ha-1 ---------


0 8 3 6 6
56 32 12 21 22
112 38 21- 38 32
168 48 49 47 41
224 58 33 36 42

LSD 0.05 12 9 8


-1
------------------ P kg ha-1-- --------


0 1.3 0.9 2.0 1.4
56 4.4 2.5 6.9 4.6
112 5.4 3.9 11.7 7.0
168 8.1 4.4 14.8 9.1
224 8.1 5.0 7.6 6.9

LSD 0.05 3.1 1.6 3.5


-1
------ ----------- K kg ha ----------


0 2.3 1.1 2.4 1.9
56 8.4 4.3 7.9 6.9
112 9.1 6.4 13.3 9.6
168 9.8 8.3 16.0 11.3
224 10.4 7.2 7.7 8.4

LSD 0.05 3.0 2.5 4.0







88


Table 3-6. Continued


Location

N Treatment Average
1 2 3



kg N ha-1 ------------ Ca kg ha-1


0 0.13 0.11 0.15 0.13
56 0.51 0.33 0.29 0.38
112 0.49 0.68 0.52 0.56
168 0.44 0.80 0.68 0.64
224 0.50 0.64 0.45 0.53

LSD 0.05 0.22 0.27 0.21

-I
------------------ Mg kg ha -----


0 0.80 0.50 1.00 0.80
56 3.06 2.00 2.80 2.60
112 3.80 3.30 5.20 4.10
168 5.20 4.50 6.70 5.50
224 4.68 3.60 3.70 4.00

LSD 0.05 1.60 1.20 1.80

-1
------------------ Fe g ha -----------


0 2 2 4 2
56 9 6 17 11
112 7 10 33 17
168 6 10 36 21
222 18 11 27 19

LSD 0.05 3 3 10







89


Table 3-6. Continued


Location

N Treatment Average
1 2 3



kg N ha-1 ------------------Mn g ha-1


0 1.0 0.6 1.4 1.0
56 4.0 2.3 3.4 3.0
112 3.0 3.7 5.6 3.0
168 6.0 4.5 7.3 6.0
224 5.0 5.3 4.0 5.0

LSD 0.05 1.0 1.5 2.0


-1
------------------ Cu g ha-1 ------------


0 0.2 0.1 0.1 0.1
56 0.7 0.4 0.5 0.5
112 0.8 0.8 0.8 0.8
168 1.1 1.0 1.0 1.0
224 1.1 0.9 0.6 0.8

LSD 0.05 0.3 0.3 0.1


-1
------------------ Zn g kg-1 -----------


0 1.0 0.8 2.0 1.0
56 4.0 3.0 5.0 3.0
112 4.0 5.0 8.0 6.0
168 5.0 6.0 9.0 7.0
224 5.0 5.0 5.0 5.0

LSD 0.05 2.0 2.0 2.0







90


Table 3-7. Responses of stalk nutrient content of grain sorghum to
rates of anhydrous ammonia.


Location
N Treatment Average
1 2 3



kg N ha-1 ------------------ N kg ha-1 -----


0 9 14 4 9
56 15 27 8 17
112 13 36 11 26
168 33 48 17 33
224 44 64 26 45

LSD 0.05 7 12 4


-1
------------------ P kg ha-1 -----------


0 4.0 5.0 2.0 4.0
56 6.0 7.0 3.0 6.0
112 11.0 10.0 3.0 8.0
168 8.0 11.0 3.0 8.0
224 8.0 12.0 4.0

LSD 0.05 2.0 3.0 NS


-1
----------------- K kg ha1 -----------


0 20 29 9 19
56 37 63 31 44
112 53 79 44 59
168 50 94 44 63
224 60 94 29 61

LSD 0.05 10 19 10







91


Table 3-7. Continued


Location
N Treatment Average
1 2 3



kg N ha- -----------------Ca kg ha-1


0 2.0 3.0 1.0 2.0
56 5.0 8.0 5.0 6.0
112 7.0 10.0 10.0 9.0
168 8.0 10.0 11.0 10.0
224 8.0 12.0 9.0 10.0

LSD 0.05 1.0 3.0 2.0


-1
------------------ Mg kg ha-1


0 3.0 4.0 1.0 3.0
56 7.0 10.0 3.0 7.0
112 10.0 14.0 5.0 10.0
168 10.0 15.0 5.0 10.0
224 12.0 14.0 5.0 10.0

LSD 0.05 2.0 4.0 1.0


-1
------------------ Fe g ha1 ------------


0 12 20 6 13
56 24 60 15 33
112 32 70 22 41
168 31 40 25 32
224 44 50 21 38

LSD 0.05 7 30 6







92


Table 3-7. Continued


Location

N Treatment Average
1 2 3



kg N ha- --------- Mn g ha- ---


0 6 8 5 6
56 12 19 16 16
112 16 23 20 20
168 19 23 22 90
224 19 25 15 20

LSD 0.05 4 8 3

-I
------------------ Cu g ha-1 -----------


0 0.5 0.8 0.2 0.5
56 0.9 1.7 0.5 1.0
112 1.4 3.0 0.7 1.7
168 1.2 3.0 0.8 1.7
224 1.8 3.0 0.8 1.9

LSD 0.05 0.1 0.6 0.1


------------------ Zn g kg-


0 3 6 2 3
56 4 12 5 7
112 5 14 5 8
168 6 14 5 8
224 7 16 5 9

LSD 0.05 1 4 2



NS = Not significant at the 0.05 level of probability.







93


Table 3-8. Response of grain sorghum grain and stalk organic matter to
rates of anhydrous ammonia.


Location
Average
N Treatment 1 2

Grain Stalk Grain Stalk Grain Stalk


kg N ha-1 ------- --- --- OM dag kg ---- -----

0 97.5 93.8 98.3 94.9 97.9 94.4
56 97.8 94.8 96.5 94.7 97.2 94.7
112 97.5 95.5 97.2 94.5 97.4 95.0
168 97.2 95.8 96.8 93.9 97.0 94.9
224 97.6 95.7 96.3 97.8 97.0 96.8
LSD 0.05 NS* NS NS 1.5

--------------------- OM Mg ha-1 -----

0 0.5 1.5 0.2 2.0 0.40 1.80
56 1.9 2.8 0.7 4.4 1.30 3.60
112 1.8 3.5 1.1 5.5 1.90 4.50
168 2.2 3.7 1.4 5.4 1.80 4.60
224 2.4 3.9 1.3 6.3 1.90 5.10
LSD 0.05 0.6 0.5 0.4 1.2

-1
------------------- IVOMD dag kg1 ----

0 63.9 46.2 69.4 51.2 66.7 48.6
56 58.1 46.6 64.5 51.0 61.3 48.8
112 61.2 59.5 60.2 56.5 60.7 58.0
168 59.5 59.8 66.8 55.6 63.2 57.7
224 60.0 55.0 68.9 57.2 64.4 56.1
LSD 0.05 NS 5.7 7.9 4.2

-1
--------------------- DOM Mg ha1 ------

0 0.3 0.7 0.1 1.1 0.2 0.9
56 1.1 1.4 0.5 2.4 0.8 2.0
112 1.1 2.2 0.7 3.3 0.9 2.8
168 1.3 2.3 1.0 3.2 1.2 2.8
224 1.5 2.4 1.0 3.7 1.3 3.0
LSD 0.05 0.4 0.7 0.3 0.8


NS = Not sinificant at the 0.05 level of robability.
NS = Not significant at the 0.05 level of probability.




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PAGE 1

ANHYDROUS AMMONIA NITROGEN FOR TROPICAL CORN, GRAIN SORGHUM, AND BAH I AGRA SS SOD IN MULTIPLE CROPPING MINIMUM TILLAGE SYSTEMS BY JOHN A. BALDWIN DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1985

PAGE 2

ACKNOWLEDGEMENTS There were many people who contributed to the completion of this work and deserve special mention. 1 would like to express my gratitude to my chairman, Dr. Raymond N. Gallaher, for his contribution to my education both in and out of the classroom. My committee members, Dr. Jerry M. Bennett, Dr. Jimmy G. Cheek, Dr. John E. Moore, and Dr. Roy D. Rhue, also made important contributions to the completion of this work. A special mention is made to Dr. W. G. Blue who had to withdraw from my committee due to an assignment in Camaroon, Africa. His guidance and support are sincerely appreciated. The on-farm research projects were made possible only through the efforts and support of the following individuals. Spencer and Peggy Miller of Miller Crest Farms, Bronson, FL; Danny Stevens and Don Bennink of North Florida Holsteins, Bell, FL; Bobby Lott, Bronson, FL; and Frank Quincy, Chiefland, FL. I thank Mr. J. F. Copeland and his son, Bill, for use of their anhydrous application equipment. I would also like to thank the following individuals for their resources and technical support of this research: Sonny Tomplins, Shawn Costello, David Block, Bill Carter, Betty Hurst, Evelyn Bluckhorn, and Anthony Drew, Technical Assistants and Extension workers, IFAS, Gainesville and Bronson, FL. ii

PAGE 3

I also want to thank the Levy County Commissioners, Sammy Yearty, Chairman, Donald Holmes, Elmer Smith, J. L. Townsend, and Mike Davis, for their support and allowing me absence from my position as Levy County Extension Director when necessary to pursue this degree program. Lastly, but most importantly, I would like to give a special thanks to my wife, Marilyn, and sons, Matt and Jason, for their moral support, willingness to pitch in and help when it was most needed, and the sacrifices which they made in their personal lives which allowed me to complete this work. iii

PAGE 4

TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ii ABSTRACT vi CHAPTERS 1 LITERATURE REVIEW 1 Introduction 1 No-Tillage multicropping Corn and Sorghums in Sods 2 Nitrogen Fertilization of Corn and Sorghum 6 Nitrogen Fertilization of Bahiagrass 10 Dry Matter Accumulation and Mineral Composition of Corn and Sorghum 17 2 ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR TROPICAL CORN PLANTED INTO BAHIAGRASS SOD BY MINIMUM TILLAGE METHODS 25 Introduction 25 Materials and Methods 28 Results and Discussion 34 Conclusions 68 3 ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR GRAIN SORGHUM PLANTED INTO BAHIAGRASS SOD BY MINIMUM TILLAGE METHODS 71 Introduction 71 Materials and Methods 73 Results and Discussion 74 Conclusions 107 4 YIELD AND CHEMICAL COMPOSITION OF BAHIAGRASS AS INFLUENCED BY NITROGEN RATE, SOURCE, AND APPLICATION METHODS 109 Introduction 109 Materials and Methods Ill Results and Discussion 115 Conclusions 139 iv

PAGE 5

Page 5 ACCUMULATION OF DRY MATTER AND NUTRIENT UPTAKE OF TROPICAL CORN, GRAIN SORGHUM, AND FORAGE SORGHUM 145 Introduction 1^5 Materials and Methods 149 Results and Discussion 150 Conclusions 6 SUMMARY AND CONCLUSIONS 172 APPENDICES A ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR TROPICAL CORN PLANTED INTO BIAHAGRASS SOD BY MINIMUM TILLAGE METHODS 182 B ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR GRAIN SORGHUM PLANTED INTO BAHIAGRASS SOD BY MINIMUM TILLAGE METHODS 204 C YIELD AND CHEMICAL COMPOSITION OF BAHIAGRASS AS INFLUENCED BY NITROGEN RATE, SOURCE, AND APPLICATION METHOD 226 LITERATURE CITED 23i BIOGRAPHICAL SKETCH 246 v

PAGE 6

Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy ANHYDROUS AMMONIA NITROGEN FOR TROPICAL CORN, GRAIN SORGHUM, AND BAHIAGRASS SOD IN MULTIPLE CROPPING MINIMUM TILLAGE SYSTEMS By John A. Baldwin December 1985 Chairman: Raymond N. Gallaher Major Department: Agronomy Nitrogen is the largest and one of the most expensive fertilizer components used in growing corn ( Zea mays L.), sorghum ( Sorghum bicolor L. Moench) and bahiagrass ( Paspalum notatum Flugge) in the United States. The first study investigated the effect of anhydrous ammonia N on the yield and chemical composition of tropical corn and grain sorghum when planted by no-tillage management into bahiagrass sod. The experiments were conducted at three locations and arranged in randomized complete block designs with six replications at five N rates (0, 56, 112, 168, and 224 kg N ha" 1 ). A second study was conducted to determine the effect of rates (as stated above) and sources of N on the yield and chemical composition of bahiagrass forage. Nitrogen rates were whole plots and sources of N (anhydrous ammonia vs. ammonium nitrate) were split plots replicated four times. vi

PAGE 7

A third study was conducted to determine the effects of anhydrous ammonia at one rate (168 kg N ha ^) on the dry matter (DM) accumulation and nutrient concentration and content of tropical corn, grain sorghum, and forage sorghum. Tropical corn showed a grain yield increase to 56 kg N ha ^ at locations 1 and 3 and to 112 kg N ha 1 at location 2. The corn grain to residue ratio, averaged over three locations, increased 280% over the control due to increased N fertility. Grain, residue, and whole plant DM yields increased to only 56 kg N ha 1 at two locations which was probably due to insufficient rainfall during the silking to ear fill period. Grain sorghum DM yield for grain and whole plant increased to 56 kg N ha" 1 at two locations. Grains and whole plant DM yield increased to 112 kg N ha 1 at location three. Insufficient rainfall and distribution of rainfall affected corn yields more than sorghum yields. When anhydrous ammonia was compared to ammonium nitrate as sources of N for bahiagrass, no differences in DM yield were found. Nitrogen, in vitro organic matter digestibility (IVOMD), and P concentrations increased with increased rates of N and were greater when ammonium nitrate was used as the source of N. The concentration of all nutrients studied responded to all rates of N. Dry matter accumulation and nutrient content of tropical grain sorghum, and forage sorghum increased rapidly following early vegetative growth. Nitrogen, P, K, Ca, Mg, Fe, Mn, Cu, and Zn concentrations increased rapidly during early vegetative growth and decreased rapidly thereafter. vii

PAGE 8

CHAPTER 1 LITERATURE REVIEW Introduction Vast areas of the southeastern United States are occupied by perennial grass sods which could be more fully utilized if interplant multicropping minimum tillage systems were feasible. Also, there are more than 16 million acres of Entisol and Ultisol soil types which make up a major portion of the ridge throughout south, central, and north Florida. These soils may produce different growth habits in corn, sorghum, and forage growth which needs to be researched. Florida is a grain deficient state, and utilization of existing sods for interplanting grains would allow more efficient utilization of capital, time, labor, and resources. Producers throughout the state are currently facing depressed prices for field crops and livestock, which makes the need for sound management decisions and best utilization of resources a necessity to continue in the risky business called "farming." Costs for establishing bahiagrass ( Paspalum no tat urn L. Flugge) sod have increased as have costs for producing other commodities. The value of this forage crop in rotations with other crops is well established, and the ability to interplant corn ( Zea mays L.) or grain sorghum ( Sorghum bicolor L. Moench) into this sod while maintaining the sod for fall regrowth would be desirable. Throughout most of Florida, bahiagrass is the predominant improved forage for grazing by cattle. This pasture 1

PAGE 9

2 grass is easily maintained and provides beef cattle producers with an acceptable forage for grazing during late spring, summer, and early fall. The productivity and quality of bahiagrass can be improved by proper application of N fertilizer. However, with low beef prices and increased cost for N fertilizer, much of this pasture is never fertilized adequately for good forage quality and productivity. With anhydrous ammonia being one of the least expensive sources of N, this fertilizer material might lend itself to use in interplant cropping systems in sod or for use as the main source of N for bahiagrass pasture fertilization. No-Tillage Multicropping Corn and Sorghums in Sods No-tillage and other forms of minimum tillage have gained popularity rapidly during the past decade, especially in the midwestern and southeastwern United States. Compared to conventional tillage systems, no-tillage and other types of minimum tillage can offer several advantages, including increased soil moisture availability (Blevins et al., 1971; Gallaher, 1977), reduced soil erosion loss (Langdale and Leonard, 1982), less planting delays, and fuel savings (Robertson and Prine, 1978). In addition, no-tillage practices allow growers to utilize crop residues and mulches more effectively for soil improvement and crop protection. Probably the major contributing factors to yield response from the use of mulch are increased water infiltration and reduced losses from water runoff (Langdale and Leonard, 1982). By covering the exposed soil surface, mulches reduce water loss from evaporation as well as reduce erosion losses due to wind and water. Mulches may also be used as a soil amendment by increasing water

PAGE 10

holding capacity and providing new cation exchange sites for improved nutrient retention. Many multicropping farmers are increasing their chances for success by utilizing no-tillage or no-tillage plus subsoiling to plant one or more crops in their multicropping system (Gallaher, 1980). Multicropping no-tillage farming requires a high level of management that most producers have not experienced (Gallaher, 1980). No-tillage has numerous advantages over conventional tillage planting management. No-tillage reduces erosion (Moldenhauer and Amemiya, 1969) No-tillage conserves soil moisture when plantings are into a chemically controlled mulch crop and indications are that a more vigorous root system develops to aid in withstanding drought stress (Gallaher, 1977). Moisture availability to plant roots throughout the growing season is one of the most critical factors limiting crop yields Crop water stress is influenced by the total water available to the plant, stage of growth of the plant, and the rate of evapotranspiration The magnitude of crop yield reduction is directly dependent upon the duration and severity of water stress. According to Gallaher (1978) mulch tillage is one system used to help conserve soil moisture and includes leaving residues from previous crops or utilizing chemically supressed sods on the soil surface in which to plant crops by no-tillage or other minimum tillage methods (Adams et al. 1973, 1970; Bennett et al., 1976; Blevins et al., 1971; Fink and Wesley, 1974; Griffith et al., 1973; Jones et al. 1969; Moschler et al., 1973; Shear and Moschler, 1969). Properly utilized mulch can result in significant increases in yields of corn (Blevins et al., 1971; Gallaher, 1977; Jones et al., 1969; Moody et al. 1963; Shanholtz and Lillard, 1969). Mulch material also reduces loss of

PAGE 11

4 water from the soil by evaporation (Jones et al., 1969; Moody et al., 1963; Shanholtz and Liliard, 1969). In a Georgia study, no-tillage of corn using a rye ( Secale cereale L.) crop as mulch as opposed to removal for hay resulted in 3260 kg ha 1 more corn or a 46% increase in yield. Conservation and better utilization of moisture was the attributing factor to better yields from the rye mulch (Gallaher, 1977). Nelson et al. (1977a, b) in no-tillage plantings of corn or grain sorghum following wheat ( Triticum aestivum L.) or barley ( Hordeum vulgare L. ) found that no-tillage corn and grain sorghum produced higher yields when early planted (after small grain for forage) than when planted late (after small grain for grain). Small increases observed for irrigated early-planted no-tillage corn and grain sorghum were attributed to a higher soil water content on non-irrigated no-tillage crops. Gerik and Morrison (1984) found no differences in yield between no-tillage and conventional planted grain sorghum following wheat, and there were trends toward better soil water content under the no-tillage throughout sorghum development each year of the study. A Virginia study showed that mulched treatments, whether of undisturbed killed orchardgrass ( Dactylis glomerata L.) sod on no-tillage plots or of wheat straw on conventional plots, gave the lowest water runoff and highest soil water content and yield of corn (Jones et al., 1969). Another Virginia study showed a 1440 kg ha 1 yield increase of corn from no-tillage in orchardgrass sod versus conventional tillage. This was attributed to less water runoff, less evaporation, and negiligible erosion (Shanholtz and Liliard, 1969). Elkins et al. (1979) no-tillage planted corn into tall fescue ( Festuca arundinacea Schreb.) and found that it was possible to obtain good corn yields while maintaining at

PAGE 12

least 50% of the grass sod with little or no erosion observed. This method offers the potential for a combination of corn production and grazing on erosive land. According to Gallaher (1980) several reports have been published in Florida on minimum tillage of crops in grass sod (Lundy et al. 1974; Prine, 1967; Robertson et al. 1964; Prine and Robertson, 1968; Robertson et al., 1976). None of these studies involved the use of no-tillage in-row subsoil planting. Three studies have been conducted utilizing in-row subsoiling when corn or sorghum was no-tillage planted into bahiagrass sod, but none of these studies utilized anhydrous ammonia as a source of N (Gallaher, 1978; Robertson et al., 1980; Stanley and Gallaher, 1980). Gallaher (1978) reported that grain sorghum tended to yield about the same for no-tillage versus conventional tillage in a bahiagrass sod. Bahiagrass was effectively controlled by preapplication of glyphosate (isopropylamine salt of N-(phosphonometryl) glycine) (Roundup) and post direct application of Paraquat (l,l'-Dimethyl-4,4'-bipyridinum ion) in this study. Robertson et al. (1980), using subsoil planting into bahiagrass sod, found there was a large response to subsoiling for both the no-tillage and conventional method of tillage, but a greater response with no-tillage. The yield responses, over tillage methods, for subsoiling were related to stand. Stands (plants ha" 1 ) were improved by subsoiling but more so for no-tillage than conventional. Forage yields correlated with grain yields but bahiagrass regrowth yields at harvest were better when corn yields were low. This suggests that the better groundcover of the higher yielding treatments shaded out undergrowth. For the 3 years of the experiments, grain yields for no-tillage were superior or as good as the conventional method when narrow rows were used and the soil was

PAGE 13

6 subsoiled beneath the row to 35 cm. Stanley and Gallaher (1980) with early planted corn into bahiagrass sod, reported after 2 years of study that corn yields of up to 9400 kg ha ^ can be realized with no-tillage practices on bahiagrass sods; however, these plots were under limited irrigation management. Nitrogen Fertilization of Corn and Sorghum The rapidly increasing cost of crop production is forcing an interest in practices that reduce or eliminate specific cost variables normally associated with crop production. Some practices which have been shown to be beneficial in reducing production costs are reduced tillage, double cropping, and crop rotations. Other methods used to cut production costs include reductions in fertilizer usage, plant populations, and herbicide usage. Excessive reduction in any of these and similar essential items may reduce crop yield below an economical level and actually increase rather than decerase production costs (Touchton, 1980). Anhydrous ammonia is one of the cheapest sources of N which could be used in no-tillage multicropping systems for corn and grain sorghum. Nitrogen fertility is an important factor in obtaining maximum yields of corn or sorghum (Anderson et al., 1985). The response of corn to increased N fertility differs considerably. Some experimental hybrids show increases in protein content and/or grain yield as rates increase (Kamprath et al., 1973; Warren et al., 1980; Nelson, 1956). Anderson et al. (1985) reported that prolific (more than one ear per plant (genotypes maintained a greater N utilization efficiency than the semiprolific genotypes at all N fertility levels and showed a greater

PAGE 14

decrease in N utilization efficiency as N fertilization was increased. The genetic selection for prolificacy under low N fertility may lead to identification of genotypes with more efficient N utilization. In a study to determine the response of grain sorghum and corn to applied N, Lutrick (1978) found that in general the yield of grain sorghum and corn did not increase significantly when more than 75 kg N ha ^ was applied on a yearly basis. The protein concentration increased in the grain of sorghum and corn for increments of N up to and including 112 kg N ha _1 Perry and Olson (1975), studying the effect of N fertilization on yield and quality of corn and sorghum residues, observed that grain N concentration increased with N fertilization in both crops. Grain sorghum N concentration was generally equal to or greater than corn. Residue yields of both crops were increased significantly by 90 kg N ha" 1 with no further increase at the higher N rate. Corn grain/stover ratios increased with increasing N levels. Crude protein of grain sorghum residues was consistently higher than corn while in vitro organic matter digestibility (IVOMD) values were consistently lower in grain sorghum. Crude protein increased significantly in grain sorghum residue with each increasing N level while little increase occurred in corn. Perry and Olson (1975) observed that corn dry matter (DM) yields declined as much as 30% within 100 days of harvest. Any decline in crude protein and digestibility following grain harvest of corn and grain sorghum appears to be associated with environmental factors. Touchton (1980) and Touchton and Hargrove (1982) stated that some of the cheaper N fertilizers are more susceptible to losses through ammonia volatilization than the more expensive ones. These losses are

PAGE 15

8 often accelerated with surface applications in no-tillage systems. Climatic and soil conditions that determine the potential for ammonia volatilization are numerous and whether or not losses will occur in any particular system are difficult to predict. Mengel et al. (1982) found that injecting NH^ or urea ammonium nitrate (UAN) below the surface resulted in consistently higher corn grain yields than applying UAN, NH, NO. or urea directly on the soil-residue surface. Nitrogen concen4 3 tration in the leaf and grain also reflected an increase in N use efficiency with subsurface N placement. Percent N in leaf was significantly higher where NH^ or UAN were injected as compared to UAN or urea surface applied. Eckert (1981) stated that research has shown little if any differences in corn yield as a result of using different N sources in conventional tillage production systems. However, the same was not true for no-tillage systems due to crop residues which may intercept much material and hold it above the soil surface until rainfall washes it into the profile. Prolonged contact with crop residues may cause loss of applied N and reduce yield. The extent of N loss will be affected by the type of N fertilizer, the application method used, soil surface pH, soil drainage, climate, and the nature of the crop residue. Eckert (1981) reported that anhydrous ammonia is the preferred source of N in no-tillage systems. Since this material is injected into the soil, it does not interact with surface residue and no problems associated with tillage or residue are normally encountered. Subsurface N application has less effect on surface pH, making it easier to maintain a favorable pH for weed control. Smith (1966) stated that the effect of rate of N application can be quite variable, depending on the crop under consideration.

PAGE 16

Because of its ability to utilize large amounts of N, the corn crop is almost ideally suited for use of ammonia. It is well established that low rates of ammonia application are not likely to appreciably influence grain protein content, although yield may be substantially increased. Colliver and Welch (1970) conducted experiments to study the effects of preplant anhydrous ammonia on germination and early growth of corn. Corn was planted directly over and parallel to NH^ bands applied at different rates, depths, and times before planting. Injurious effects on corn observed with certain NH^ treatments were reduced stand, stunted early growth, restricted seedling root development, and increased occurrence of P deficiency symptoms. Increasing depth of application was more effective at reducing injury than was increasing the time interval between application and planting. Injury was largely prevented when application depth was 25 cm, for all times and rates of application. Mills et al. (1974) reported that toxicity may be partially overcome if the soil pH is near neutrality. The principal factors affecting NH^ + losses from soil are soil reaction and the amount of NH^ + N applied, but depth of fertilizer placement, cation exchange capacity (CEC) base saturation, and soil moisture content also affect retention and volatilization of NR^ + (Mills et al., 1974). Gomes and Loynachan (1984) stated that the nitrification of ammonium to nitrate is a stepwise biological oxidation in which NH. + ions are con4 verted to nitrate (NG^) mainly by the bacteria of the genus Nitrosomonas, and N0 2 is further oxidized to NO^ by Nitrobacter. The end product of nitrification (N0 3 ) is not strongly attached to the soil's cation exchange sites and, thus, is subject to leaching losses by percolating water. Fenn and Kissel (1976) reported that an increasing

PAGE 17

10 CEC resulted in decreasing NH^ + losses. Increased depth of incorporation resulted in reduced NH^ + losses. Also, decreasing the soil water increased the effectiveness of soil incorporation for reducing NH^ + losses. Boswell (1977) stated that the agronomic efficiency of anhydrous ammonia is reported to be equal to other N sources, inferior in some studies, and superior to the conventional N fertilizers under some conditions. Various workers recognized that different soil types as well as application depth, play a major role in predicting ammonia sorption. In addition, moisture content, tilth, pH, distribution as influenced by applicator spacings, and temperature have been shown to influence the availability of N from anhydrous ammonia. Nitrogen Fertilization of Bahiagrass There are 5 million acres of improved bahiagrass pasture in the southeastern United States. This pasture grass is easily maintained and provides beef cattle producers with an acceptable forage for cattl to graze during late spring, summer, and early fall. The yield and quality of bahiagrass can be improved by proper application of N fertilizer (Beaty et al., 1960, 1977; Blue, 1966, 1972, 1974; Stanley et al., 1977). However, with low beef prices and increased cost for N fertilizer, much of this pasture is never fertilized adequately for good forage quality and productivity. Nitrogen is the largest and one of the most expensive components of bahiagrass fertilization. While anhydrous ammonia is one of the least expensive sources of available N, research in the 1950 's conducted by Blue and Eno (1954) and Blue (1984) indicated that a loss of up to 40% of applied N could occur due to volatilization of ammonia.

PAGE 18

1] This loss was dependent upon the cation exchange capacity of the soil, soil temperature, moisture, pH of the soil, and spacing of injectors. Since the 1950's, new and improved application equipment is in use that may make the utilization of anhydrous ammonia more economical than other sources of N. The cost of N from ammonium nitrate (34% N) is 2.4 times that of anhydrous ammonia (82% N) Many studies have been conducted concerning the use of various N rates and sources for fertilization of bahiagrass and other tropical forages (Beaty et al., 1960, 1963, 1977, 1980; Blue, 1972, 1974, 1977). Follett and Wilkinson (1985) reported that effectiveness of N sources varies with placement, soil, and environmental conditions. Ammonium nitrate often has the highest recovery efficiency. Losses of NH 4 + can occur from surface-applied urea, resulting in a lower efficiency of N use. Anhydrous ammonia fertilizers are usually the lowest priced per unit of N and have low loss rates if properly injected into the soil (Follett and Wilkinson, 1985). Nitrogen is the main limiting nutrient in many forage systems; as a consequence, large yield increases are obtainable with N fertilization (Dougherty and Rhykerd, 1985). When N is applied to grasses, the higher crop growth rates achieved are most often attributable to increased leaf area indices (LAI). Nitrogen-fertilized grasses have larger cells with thinner cell walls and, as a consequence, have larger leaves. Nitrogen also stimulates meristematic activity; which is often reflected in increased tillering. Leaf senescence is also retarded by N fertilization which helps to maintain the photosynthetically active surface (Dougherty and Rhykerd, 1985).

PAGE 19

12 Beaty et al. (1980), in a study of N rates on bahiagrass yields, reported that forage production efficiency of applied N (kg DM produced kg ^ N applied) decreased from 54.6 for the first 84 kg N ha ^ to 34.0 for the additional N from 84 to 168 kg N ha 1 and further to 5.2 for N from 168 to 336 kg N ha _1 They stated that with unfertilized bahiagrass, N should be applied by or before early March, but after the first year, time of N application makes no practical difference in yield. At low N rates, harvesting to a stubble height of 3 cm or less will significantly increase the amount of forage utilized and harvested. It was concluded that close grazing or clipping of 'Pensacola' bahiagrass (1) increases digestibility by keeping the forage green; (2) increases the effective yield of a pasture; and (3) may provide better forage distribution over a season without affecting yield when split applications of N are made. Most bahiagrass forage is produced by vegetative tillers which terminate in stolons and bear their meristems, including the leaf growing points, at the soil surface. Leaf production is continuous during the summer (Beaty et al., 1977) and the stolons may be utilized as a feedstuff for beef cattle (Rodriquez et al., 1973). Some tillers develop flowering culms which account for a substantial portion of the July to August growth, but for only a small amount of the total season's forage. Forage production of 'Pensacola' bahiagrass as affected by N rates at a clipping height of 6 to 7 cm has been established and subsequent studies by Stanley et al. (1977) using clipping heights from 0 to 15 cm showed forage yields were negatively related to height of clipping. Tropical grasses have been reported to grow better than temperate grasses at low N levels. One reason may be that temperate grasses have

PAGE 20

13 a higher proportion of roots, thereby reducing the amount of N available for top growth (Wilson and Haydock, 1971). Another reason may be that tropical grasses generally have lower N concentrations, partly because of higher proportions of stem and sheath tissue (Mott, 1974). Usually 50-80% of N applied to forage grasses is recovered in the harvested DM (Lazenby, 1983). Recovery may exceed 100% if fertilizer N increases the availability of soil N. Recovery is dependent on rate and time of application, source of N, soil N availability, species, temperature, moisture, and the interval between application and harvest (Dougherty and Rhykerd, 1985). Limited information is available on the response of bahiagrass to anhydrous ammonia as a fertilizer source of N. The efficiency of using anhydrous ammonia in comparison to other sources of N on various crops has been studied by many investigators (Smith, 1966). Tucker and Crowe (1966) summarized the results of many investigations testing the effectiveness of various sources of N on several crops in comparison to anhydrous ammonia They concluded that anhydrous ammonia was equal to most other N sources. The results of most experiments on forage indicate that, during the year of application, yields are somewhat higher from grasses fertilized with ammonium nitrate in split applications than with anhydrous ammonia applied in one application at rates of 112 to 324 kg N ha" 1 (Tesar, 1974). Burton and Jackson (1962) conducted trials on 'Coastal' Bermudagrass ( Cynodon dactylon L.) for 5 years utilizing anhydrous ammonia as one source of N. The anhydrous ammonia was applied in 40 cm rows with a chizel-type knife. Total yields were greater for ammonia nitrate fertilized grass at the 112 and 224 kg rates of N when fertilizer was applied in split applications.

PAGE 21

14 When Che fertilizer was applied in one application in mid-March, anhydrous ammonia was equal to ammonium nitrate in effectiveness. Hill and Tucker (1968) found yields equal for all sources and all clippings at lower rates of N application. At higher rates of N application, anhydrous ammonia produced lower yields in the first clipping and higher yields in succeeding clippings. This lag in response was attributed to sod burn from escaping ammonia. Reducing the applicator knife spacing tended to increase NH^ retention, decrease sod burn, and increase the NH^ efficiency at the high rates of N application. Newer and more effective application equipment may be the cause of the increased application efficiency. Lechtenberg et al. (1974), using anhydrous ammonia to fertilize smooth bromegrass ( Bromus inermis Leyss.), found that it was as effective in increasing animal production per hectare as was ammonium nitrate at the same application rate. Increasing the N fertilizer for tropical forages has been shown to increase DM yield and crude protein content. However, more diverse information is available on the effect of N rate and environmental factors on the digestibility of tropical grasses. Moore et al. (1970) reported that 'Pensacola' bahiagrass hays of varying maturities differed in crude protein content from 10.5 to 7.6% after 2, 4, and 6 weeks of growth and from 7.0 to 5.2% after 10 or more weeks of growth. In vitro organic matter digestibility (IVOMD) varried from 63.0 to 60.7% after 2, 4, or 6 weeks of growth and from 53.3 to 46.0% after 10 or more weeks growth. They concluded that 'Pensacola' bahiagrass has a potentially good quality in terms of voluntary intake and nutrient digestibility. However, quality did decline quite rapidly between 6 and 10 weeks of growth. Low crude protein content may be the primary

PAGE 22

L5 factor limiting quality at the 10-week growth stage while low nutrient digestibility may be the primary limiting factor at later stages of maturity. Van Soest (1985) also reported that most forages decline in nutritive quality with age. He stated that age and physiological maturity are not identical. Thus, factors such as cool temperatures and light that retard maturity promote higher quality at a given age. Most date-of-cutting studies represent first cuttings taken during the spring and early summer, when the effects of the warming season and maturity positively interact. Such studies show steep declines in digestibility and protein and increases in fiber, lignin, and other cell wall components. Date-of-cutting information is less useful in evaluating second cuttings or aftermaths grown in July through September. At this time, environmental temperature is maximum and no longer increasing, and digestibilities are not as high in immature material as they were in the spring. As temperatures decline in the fall, nutritive value may actually increase with the age of the plant (Van Soest, 1982). The tropical environment differs in that there is generally a much higher solar intensity, which, in combination with adequate moisture and high temperature, means extremely rapid plant development and growth toward maturity. Van Soest (1985) stated that crude protein content as influenced by fertilizer N is the most important effect of fertilization. He also stated that digestibility is affected relatively little, although palatability may be. Wilson (1973) indicated that increasing the N supply from low to moderate levels increased digestibility by 3-5% and caused a small increase in total soluble carbohydrates in pangolagrass ( Panicum maximum var. trichoglume) Many investigators (Burton et al.

PAGE 23

16 1963; Doss et al., 1966) have demonstrated that DM yield and crude protein concentration and content of bermudagrass can be increased with increasing levels of N fertilizer. The effect of N fertilization on digestibility has not been demonstrated as frequently. Meredith (1963) reviewed 22 papers where high and low levels of N had been used on a number of species, including bermudagrass, and concluded that less than a 1% increase in digestibility was due, on the average, to higher rate of N. Fribourg et al. (1971), using 'Midland' bermudagrass, found the average digestible DM increase to be from about 37 to 46% over the range of applied N. The greatest increase occurred as the N rate was increased from 133 to 400 kg N ha \ Henderson and Robinson (1982a) stated that in the southeastern United States the climate during the growing season of summer perennial grasses is characterized by considerable fluctuations in temperature, solar radiation, and rainfall. These climatic fluctuations have been associated with seasonal variations in yield and forage quality of the warm-season grasses (Henderson and Robinson, 1982a). Growth rates of most tropical grasses increase with temperature to 30 to 35 C and increase with light intensity to 60,000 lux or higher. Conditions favoring maximum growth rates have frequently resulted in reduced forage quality. High temperatures during growth periods have been related to increased proportions of stem, increased fiber concentrations, decreased water-soluble carbohydrate concentration, and reduced herbage digestibility of tropical grasses (Henderson and Robinson, 1982a; Wilson and Ford, 1973; Wilson and Minson, 1980; Wilson et al. 1976). Henderson and Robinson (1982b), in a study of tropical grasses including 'Pensacola' bahiagrass, found that in all grasses that IVOMD

PAGE 24

17 consistently decreased as temperature increased, resulting in maximum digestibility at the lowest temperature. The effect of light on digestibility ranged from positive to negative, depending on the grass and temperature. Maximum digestibilities occurred at the high soil moisture level after 14 days regrowth. The digestibility of the 'Pensacola' bahiagrass was 3.6 percentage units higher after 14 days regrowth than after 21 days regrowth. Dry Matter Accumulation and Mineral Composition of Corn and Sorghum Increase in dry weight is a useful definition of growth for those interested in crop productivity. Knowledge of DM production and of nutrient uptake and distribution is needed to relate to plant growth and development (Jacques et al. 1975). Crop growth is usually more accurately characterized by measurement of dry weight than measurement of fresh weight, which can be strongly influenced by prevailing moisture conditions. Dry weight increase has been described mathematically as a function of physiological, pheno logical and environmental factors. Increase in dry weight with time is usually characterized by a sigmoidal curve (Leopold and Kriedemann, 1975), in which three primary phases are recognized: expansion, linear, and senescence (Richards, 1969). In the expansion phase, the growth rate (increase in dry weight per unit of time) is initially slow but the rate increases continuously as more dry weight is added. Accumulation of dry weight is exponential until self-shading or other conditions prevent the increasing leaf area from producing a proportionate increase in the weight of the plant

PAGE 25

18 (Watson, 1958; Leopold and Kriedemann, 1975; Duncan et al., 1967). The end of the expansion phase marks the beginning of the linear phase in which the increase in DM continues at a constant rate. The final, senescence phase is characterized by a decrease in growth rate as the crop approaches maturity and begins to senesce (Salisbury and Ross, 1978) The patterns of growth and DM distribution observed in tropical maize (Goldsworthy and Colegrove, 1974) suggest that the capacity of grain sink to accommodate assimilate can limit grain production. McPherson and Boyer (1977) pointed out that another potentially serious problem occurs if sink size has been affected by low leaf water potential. Moss (1962) and Allison and Watson (1966) have shown that when grain sink is limited, DM that would have passed to the grain, accumulates in the stem and husk. Anderson et al. (1985) indicated that source-sink relationships are important in the accumulation and distribution of N and DM. They found that prolific genotypes of corn maintained a greater N utilization efficiency than the semi-prolific genotypes at all N fertility levels and showed a greater decrease in N utilization efficiency as N fertilization was increased. The prolific genotypes partitioned a larger proportion of plant N to the grain at all N fertility levels, apparently by increasing N remobilization. The semi-prolific genotypes responded to increased N fertility by increasing the ear number per plant, grain N content, and grain yield. Some investigators have measured the inorganic nutrient uptake by corn and sorghums. It has been recognized that amounts of most nutrients removed by a crop harvested for silage may be much more than when the same crop is harvested for grain (Hanway, 1966).

PAGE 26

19 A considerable range in values can be expected for each element, since soil drainage and fertility, climatic conditions, plant population, crop species and genotype, and fertilizer practice can influence crop content of each element (Fribourg, 1974). Work by Owen and Furr (1967) showed little difference in the mineral nutrient content of corn and sorghum, except for K, which can be influenced by fertilization. Fribourg et al. (1976) reported the results of inorganic nutrient uptake by corn and sorghums. The amounts contained in the above-ground plant parts exhibited considerable range: 34 to 222 kg N ha ; 8 to 34 kg P ha" 1 ; 31 to 271 kg K ha" 1 ; 8 to 55 kg Ca ha" 1 ; and 9 to 45 kg Mg ha" 1 Since the quantities removed are the products of harvested plant part weights and percent composition, they are influenced not only by the climatic, edaphic, genotypic, and management considerations, but also by soil nutrient availability. Sivakumar et al. (1979) suggested that plant growth is the result of an effective integration of many factors. Restriction of growth may occur due to the limitation of any one factor. For example, water deficits in plants generally lead to reduced leaf water potentials and stomatal closure, as manifested by an increased leaf resistance to transpiration. The effects of depletion and replenishment of soil water on transpiration are of specific importance to water use and its efficiency in crop production. The relative rates of absorption and transpiration determine a plant's internal water balance, which directly affects the physiological and biochemical process of plant growth. It is widely accepted that corn grain yields are most severely reduced by water stresses which occur during the silking and tasseling stages of growth. Additional water stresses which occur later during the grain filling period can further

PAGE 27

20 reduce grain yields by reducing the weights of individual seeds. Vegetative growth has often been considered the period of corn or sorghum growth which is least sensitive to water stress (Bennett, 1984; Denraead and Shaw, 1960; Eck, 1984; Jurgens et al., 1978; Sinclair et al., 1975). Growth and DM production of grain sorghum have been reported by several workers. Vanderlip and Reeves (1972), who defined 10 growth stages of grain sorghum from emergence to physiological maturity, suggested that by using those stages as standards the timing of sampling or treating of sorghum could be described accurately in relation to the morphological or physiological age or status of the plant. They report that the general pattern of DM accumulation was the same for different grain sorghum hybrids and that late maturing hybrids tended to have higher DM at each stage of development than did earlier maturing hybrids. Jacques et al. (1974), in studies of grain sorghum hybrids, found that Ca and Mg uptake was rapid in early plant development, and Ca was generally taken up more rapidly than Mg during vegetative growth. When vegetative growth had been completed, more than half of the plant's total Ca and Mg uptake had occurred. Whole plant nutrient concentrations decreased through most of plant growth due to dilution. Zinc and Cu concentrations did not decrease as much during grain development as during vegetative growth. Lockman (1972b), reported that soil acidity, soil fertility, stage of growth, variety, and climatic conditions affected the mineral composition of grain sorghums. Jacques et al. (1975) found that 20 to 30 days after emergence sorghum plants began to grow rapidly; their dry weight increased faster than uptake of

PAGE 28

21 nutrients, thus concentrations decreased. Hanway (1962a) found that differences in soil fertility influenced the amounts of N, P, and K taken up by corn plants, but did not markedly change the seasonal pattern of uptake and distribution of these elements in the plants. The accumulation of N, P, and K in corn and grain sorghum was linear in relation to DM accumulation (Fribourg et al., 1976; Hanway, 1962b). Corn and grain sorghum production may be greatly enhanced by proper fertilization. As fertilization efficiency is highly interactive with many soil properties and climatic factors, plant analysis has been used as a measurement of the soil-plant nutrient environment. Since nutrient availability as measured by soil testing may or may not be highly correlated to final crop yields, plant analysis can be used effectively in conjunction with soil tests to examine both critical levels of nutrients needed by the crop and the ability of the soil to supply those amounts. Both of these analyses are necessary to determine nutrient cycling in multicropping systems and to refine the fertilizer requirements of a particular system. Abundant literature exists concerning plant analysis data for corn although few data are available for grain sorghum. Because of this imbalance and the observations of early researchers that the two crops contain similar amounts of most elements, they have often been discussed together. Lockman (1972a, b) and Bennett (1971), however, warn that although nutrient concentrations in the crops are similar, differences increase in later growth stages and corn data should not be used to evaluate growth sorghum. Since nutrient elements are not evenly distributed throughout a plant and fluctuate widely during its growth, it is of great importance

PAGE 29

22 to standardize time of sampling and plant part to be sampled. It is generally recommended that, for diagnostic purposes, corn be sampled by collecting 12 to 25 ear leaf samples from tasseling to silk initiation, and grain sorghum be sampled by collecting 15 to 25 samples from the second leaf from the top of the plant at heading (Jones and Eck, 1973). Whole plant sampling at physiological maturity is not a good measure of nutrient sufficiency in a plant but may be used to determine total plant content to be used in nutrient cycling determinations. Critical nutrient levels (CNL) have been the object of much controversy and may be defined in several ways (Tyner, 1946; Ulrich, 1952) but are essentially the concentration of an element below which yields decrease or deficiency symptoms appear. Because of the numerous interactions among nutrient elements themselves (Peck et al., 1969) and other confounding influences such as soil types (Gallaher and Jellum, 1976) and cultivar differences (Lutz et al., 1972), CNL values must be used with care. Tables 1-1 and 1-2 list ranges of CNL's for corn and grain sorghum. Values are for the ear leaf at silk for corn and the third leaf below the panicle at bloom for grain sorghum. Lockman (1972c) further reported that N and P levels in leaf tissue were both well correlated with sorghum grain yield but that K levels were more irregular and not as well correlated. Zinc levels exhibited a curvilinear correlation with grain yield, the correlation becoming negative as yields increased above the 6280 kg ha \ In corn, yields and nutrient concentrations in the leaf may be also highly correlated. Bennett et al. (1973) noted grain yield increases with increasing N and P levels in the ear leaf.

PAGE 30

23 u tJ >> o cd 4-1 CO C H >-i c a o 3 a c_> 3 4J CO Jj CO cfl 5 4J >. e to 4-1 H £ c M 00 •H 3 ~ CO 4-1 O 1-4 to CO 60 E CO CO o a) •H 3 4-1 u C 14-1 c a E 1) H W M CN H o -oco o in CM O O O O O O O CM O lo vd -i H -a O o o o o O u oo m CM co CM >^ CO co CO o 33 co O o O c 0) •H o •H U-l IH 3 CO o o o o o 4-1 y-i in oin o CN CM CM 3 co Z 0) CM o H o o O in O O o cm a\ , o 0 4-1 4J HI •H U co c (J ,o a cO > -J •H c 4J H c a -u D. 3 3 a tin M CJ cO u C'— > cO a) ro OJ o CO CO cn QJ CJ • — 1 ^ tic a 3 E •H C 0 a •H 3 w 4-1 0 CO M i — i U 1 — 1 CO H •H 0 CN < So un DQ r>> E Q) ja CJ) E d i — i 0 O ~3 4-1 CJ •"i CJ c 3 14-1 #% vC H c cfl U-J I C7\ E 3 Cfl H >^ 0 O u CJ w CO iH c 4-1 o 1-4 ag a 4J CJ a •3 3 cx c 3 cd 0 o oo n ^ xi c c 4J 3 3 u CO •H iJ o u U 3 a 4J 3 -3 rH >> H 4-1 O rH h CJ 1-4 3 o 3 3 3 o IH cu 4-1 CJ H 3 4-1 00 DO U E Rj a Z 0) •H si 3 u-i 4-1 3 >U cfl •H rH pel 3 3 3 3 > J) 3 M CJ •H CO •-4 cfl H 4-1 CO 4-) "3 3 a M e l — 1 a CJ so 3 r-H u H •H *! 3 0 4-1 H c CO rH H 4-1 u M H 3 0 O a ss CJ w oo W O pej 33 o oo

PAGE 31

24 o o m o o c in m cm x — N £ ss \ — u 0 c M 3 cu O H •H M x to CO 4-1 0 G< to H a (-1 0) trj 'J c iw -1 O u rH M rH •H J3 o a z Ph a, a CO -— N ^ c r S — s 3 s u > y — \ O a) PQ a G a) fa a c v — r-l -a n 0) X DO C O a. o c o a. c H tjj 0 •H Mo H u N CO <0 c c 0 • 0) (0 — — C3 ai 00 4-1 CU 3> — rH 0) X 0) < to •H 4J m 01 trj o 1-1 •H u a 00 a u UH "j O -J 4J cu H c o a •H x 14-4 ir-H CO 0 >J >• 01 4-1 c C •H m oi to 60 M X 0) U > u c •H M 14-1 C 3 0 XI to 01 > CO 3 •H 0) e X 5 4-1 c u c 0 •rt Ij Vj u 00 CS < > >, 0) trj X 4-> E trj o rH 14-4 0) > a, c (3 3J 1) O CO i— 1 u Q) to V-i 0) 0 3 e rH o •H trj > 4J 4-1 trj 0) O 4-4 •H r C
PAGE 32

CHAPTER 2 ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR TROPICAL CORN PLANTED INTO BAHIAGRASS SOD BY MINIMUM TILLAGE METHODS Introduction Nitrogen fertilizer is used in lar.ge amounts and is the most expensive input used in growing corn ( Zea mays L.) in the United States. Vast areas of the Southeast are occupied by perennial sods which could be more fully utilized if interplant multicropping mininum tillage systems were feasible. Multicropping systems utilizing bahiagrass ( Paspalum notatum L. Flugge) sod followed by temperate corn have been studied (Gallaher, 1978; Lundy et al. 1974; Prine, 1967; Prine and Robertson, 1968; Robertson et al., 1976, 1980; Stanley and Gallaher, 1980). However, only a few of these studies involved in-row subsoiling and none utilized anhydrous ammonia as the sole source of N. As mentioned, several researchers have investigated reduced or no-tillage corn production and have shown it to be advantageous over conventional tillage on land subject to erosion hazards. Robertson et al. (1976) have cited several factors that contribute to the acceptance of notillage crop production. Highly erosive land can often be utilized for no-tillage grain production without serious soil losses. Elkins et al. (1979) showed that planting into sod usually involves the use of a contact herbicide to chemically kill or suppress the grass sod. They found in their experiments that it was possible to obtain good corn 25

PAGE 33

yields while maintaining at least 50% of the grass sod with little or no erosion observed. This method offers the potential for a combination of corn production and grazing on erosive land. Some reduced or no-tillage management for cropping systems leave a layer of crop residues on the soil surface that can result in increased soil water content and reduced soil temperatures during the growing season and can lead to increased N losses through leaching and denitrif ication (Thomas et al., 1973; Unger, 1978). The increased N loss through leaching and denitrif ication has been attributed to both increased soil water content and an increased number of large pores contiguous to the soil surface (Thomas et al. 1973) Opportunities to incorporate N fertilizers below the residue layer in reduced tillage systems are limited. Consequently, the most common methods currently used in no-tillage systems are broadcasting of solid ammonium nitrate (NH^NO^) or urea or spraying urea-ammonium nitrate (UAN) solutions on the soil surface immediately before or after planting. However, significant N losses can occur through ammonia volatilization when ammonium N sources, particularly urea, are left on the soil surface and exposed to the atmosphere (Bandel et al., 1980; Ernst and Massey, 1960; Hargrove et al., 1977; Terman, 1979; Volk, 1959) A number of soil and environmental factors affect the amount of N lost through ammonia volatilization from surface-applied N fertilizers. Among these are soil pH, cation exchange capacity (CEC) soil organic matter (OM) content, amount and type of residue present, soil moisture content, temperature, humidity, and the N source used (Fenn and Kissel, 1976; Ernst and Massey, 1960; Terman, 1979). Because of the large number of interacting factors involved, the actual amount

PAGE 34

27 of NH^ + lost by volatilization is difficult to predict (Bandel et al., 1980; Fox and Hoffman, 1981; Terman, 1979). In addition to N losses from the soil-plant system, a significant portion of the N applied in no-tillage systems can become immobilized in the decaying residue mulch and, thereby, reduce the amount of N available to the growing crop (Doran, 1980). Therefore, anhydrous ammonia could be the preferred source of N in no-tillage systems. Since this material is injected into the soil, it does not interact with surface residue and no problems associated with tillage or residue are normally anticipated. Subsurface N application has less effect on surface pH, making it easier to obtain a more favorable pH for weed control (Eckert, 1981). Mengel et al. (1982) found that injecting NH^ or UAN below the surface resulted in consistently higher corn yields than applying UAN, NH^NO^, or urea directly on the soil-residue surface Corn has potential for late season planting and production of a second crop to increase productivity in the Southeast (Chambliss et al. 1979, 1980; Gallaher and Horner, 1983; Monson et al., 1980; Widstrom and Young, 1980). These studies involved tropical corn hybrids. Midto late summer plantings of temperate hybrids developed for different planting dates and environments experienced numerous pest problems (All and Gallaher, 1976, 1977; Widstrom and Young, 1980; Young et al., 1978). No-tillage planting a summer crop such as tropical corn into a grass sod could help control erosion problems due to wind or water. Therefore, methods for chemically suppressing late spring and summer grass growth, but allowing for fall regrowth would be desirable. The renovation of the pasture sod with in-row subsoiling plus having grass regrowth and crop residues for livestock to graze in the Fall could

PAGE 35

28 dramatically increase the value and profitability of multicropping corn with bahiagrass sods. The objective of this study was to determine the effect of anhydrous ammonia as the sole source of N for tropical corn planted into bahiagrass sod using minimum tillage methods. Materials and Methods Field Procedures The experiment was conducted at three locations during 1983 and 1984. The experiment was in a randomized complete block design with six replications (Table 2-1) utilizing Pioneer brand 'X304C' tropical corn planted into 15-year-old bahiagrass (c.v. 'Pensacola') sods. Location 1 was planted on June 1, 1983, on a Kershaw fine sand (thermic, uncoated typic Quartzipsamment) an excessively drained sand and location 2 was planted on June 23, 1983, on a Chief land fine sand (loamy, siliceous, thermic, Arenic Hapludalf). The third location was planted on May 29, 1984, on an Arredondo fine sand (loamy, siliceous, hyperthermic grossarenic Paleudult) Locations 1 and 3 were in Levy County, Florida, latitude 2930' North, longitude 8240' West. Location 2 was in Gilchrist County, Florida, latitude 2950' North, longitude 8240' West. Ten days prior to planting, an application of 0.84 kg a.i. glyphosate ha 1 (isopropylamine salt of N-(phosphonomethyl) glycine) (Roundup) plus 1.9 L of X-77 surfactant of 95 L of water was applied in a spray volume of 26 L ha" 1 at 2.8 kg cm This was done to suppress the bahiagrass sod prior to planting.

PAGE 36

2 9 Table 2-1. Statistical analysis model used for tropical corn data. Randomized complete block design. Source DF TOTAL 29 (rT-1) REPLICATIONS (r) 5 (r-1) TREATMENTS (T) A (T-l) ERROR 20 (r-1) (T-l)

PAGE 37

30 All plots were fertilized with a broadcast application of 80 kg K ha \ 25 kg S ha \ and 12 kg Mg ha 1 just prior to planting. Sources of K, S, and Mg were I^SO^MgSO^ (K-Mag) and KC1 (Muriate of Potash). The plots were eight rows, 76 cm wide, and 12.2 ra in length. The plots were planted with an in-row subsoil planter with anhydrous tubes attached to the subsoil shanks. Corn was planted at a population of 62,000 plants ha No irrigation was provided at any location. An application of 0.67 kg active ingredient (a.i.) Carbofuran ha 1 (2, 3-Dihydro-2 2-dimethyl-7-benzof uranyl raethylcarbamate) (15G Furadan) was applied in front of the press wheel at planting. Nitrogen was applied at planting under the row and injected on the subsoil shank at a 25 cm depth. Nitrogen rates were randomized and replicated six times at 0, 56, 112, 168, and 224 kg N ha" 1 On July 10 at location 3 and on July 26 and 27 at the other two locations, 0.05 kg a.i. paraquat ha 1 (1, 1 1 -Dimethyl-4 4 'bipyridinium ion) plus 0.5 L X-77 in 95 L of water was direct sprayed to further suppress the sod. The plots were harvested on the following dates at the three locations: September 12, 1983; September 26, 1983; and September 9, 1984. Two rows 6 m in length were hand harvested from each plot for yield determination. The samples were weighed and a five plant subsample taken for dry matter (DM) determination and chemical analyses. At 40 days post-emergence, five whole plants and five youngest mature leaves were collected from each plot for chemical analyses. At corn bloom, five ear leaves were collected from each plot for chemical analyses. Planting, plant sampling, and harvest dates are shown in Table 2-2.

PAGE 38

31 i o c a s c u o o 1-1 CO o •H a 0 ij 4-1 fo X a 4-1 CO tx c H — a g CO 00 U c CO H a • 0 c Ul to CO m go d J-4 4J Ot Rj rt -a DO cd C tH 4J 0 DO 4-> CJ c > H M cO ~ o •u TJ a c n a i— i a M C a> H 00 J C H n H — i H Cm (J CnI 1 CM CO H OA ON ON CO — c a B on O CM i — i H CM H rH h 00 ON ON m CM cm 00 CM CO nO vO 00 CM CM CM 00 ON On C O u M cd <4H O MH ct C 3 rH l-i e o o <_> rc 1 o ac )-4 — i a) CO 0 M •H a rH O 43 cd CO 0 o Cm >^ UJ ad W i — I CM CO ^3" LO vjO

PAGE 39

All plants and plant parts were dried in a forced air oven at 70 C for 48 hours and weighed. Samples were prepared for further laboratory analysis by grinding in a Wiley mill to pass a 1 mm stainless steel screen and then stored in air-tight plastic bags. Soil samples were taken during the experiment after corn harvest. Soil test results are shown in Appendix Table A-7. Laboratory Procedures For all soils, N analysis employed a micro-kjeldahl procedure (Bremner, 1965) as modified by Gallaher et al. (1976). A 2.0 g sample was placed in 25 ml digestion tubes to which 3.2 g of catalyst (90% anhydrous K^SO^, 10% anhydrous CuSO^) 10 ml concentrated ^SO^ and 2 ml 30% #2^2 were aci ded. Samples were then digested in an aluminum block digester (Gallaher et al., 1975) for 2.5 hours at 375 C. Upon cooling, solutions were diluted to 75 ml with deionized water. Nitrogen concentrations of these prepared solutions were determined using an AutoAnalyzer All soil P, K, Ca, Mg, Fe, Cu, Mn, and Zn analyses were conducted using procedures recommended by the University of Florida's Soil Testing Laboratory using a double acid extraction procedure (Mehlich, 1953). Five grams of air-dried soil were extracted with 0.05 N HC1 + 0.025 N H„S0, at a soil : solution ratio of 1 to 4 (W:V) for 5 minutes. — 2 4 Soil P was then analyzed using colorimetry. Potassium was determined by atomic emission spectrophotometry. Calcium, Mg, Fe, Cu, Mn, and Zn were determined by atomic absorption spectrophotometry. Soil pH was determined using a 2:1 water: soil ratio.

PAGE 40

33 Nitrogen analysis of plant material employed the micro-kjeldahl procedure as modified by Gallaher et al. (1976). A 0.1 g sample was placed in 75 ml digestion tubes to which two boiling chips, 3.2 g of catalyst (90% anhydrous K SO^ 10% anhydrous CuSO^) 10 ml of concentrated H„S0, and 2 ml of h\0 o were added. Samples were then digested 2 4 2 2 in an aluminum block digester (Gallaher et al. 1975) for 2.5 hours. Upon cooling, solutions were diluted to 75 ml with deionized water. Nitrogen concentration of these solutions were determined on a Technicon II AutoAnalyzer Phosphorus, K, Ca, Mg, Fe, Cu, Mn, and Zn concentrations were determined by a routine dry ashing mineral analysis procedure as modified by R. N. Gallaher (personal communication, Agronomy Department, University of Florida, Gainesville, FL, 1983) in which 1.0 g samples were placed in 50 ml pyrex beakers and ashed in a muffle furnace at 480 C for a minimum of 4 hours. After cooling, each was treated with 2 ml concentrated HC1 and heated to dryness on a hot plate. An additional 2 ml of concentrated HC1 + water was added to the dry beakers followed by reheating to boiling and then diluting to 100 ml volume with deionized water. Solutions were analyzed for P using colorimetry on an AutoAnalyzer. Potassium was determined by atomic emission spectrophotometry. Calcium, Mg, Fe, Cu, Mn, and Zn were determined by atomic absorption spectrophotometry. Organic matter was determined as the loss in weight after ashing the DM samples. In vitro organic matter digestibility (IVOMD) of plant material was determined by the Tilley and Terry (1963) two-stage procedure adapted by Moore and Mott (1974, 1976) and expressed on an OM basis (Moore et al., 1972; Moore and Mott, 1974, 1976).

PAGE 41

34 Statistical Procedures The statistical analysis included analysis of variance (ANOVA) and least significant difference (LSD) for all responses and regression analysis for orthogonal polynomials utilizing contrast statements where appropriate. The data from individual locations were analyzed separately due to an interaction between treatments and locations. Where ANOVA indicated differences (probability of F = 0.05) LSD's were employed to compare treatment means. In the cases where there was response to N fertilization rate, appropriate regression analysis was conducted. Regression terms were incorporated into the model if judged significant at the 0.05 level by the F-test or if a higher order term in the same variable was judged significant. The ANOVA, LSD, regression analyses, and correlations were performed at the Northeast Regional Data Center (University of Florida, Gainesville, FL) using the General Linear Model (GLM) procedure of the Statistical Analysis System (SAS) Data filing and transformations were performed on a Tandy Radio Shack TRS-80 Model 111 or IV (48K or 64K RAM microcomputer) Results and Discussion The success of dryland or nonirrigated crop production is dependent on precipitation during the crop growing season and available water stored in the soil. Rainfall data for the three experiments conducted during 1983-84 are found in Table 2-3. Droughty conditions were reflected in grain yields of corn with the most severe stress occurring during the silking and grain fill periods at location 1. When the data

PAGE 42

35 Table 2-3. Rainfall data during 1983-84 at three locations where tropical corn was planted into bahiagrass sod. 1983 1984 Date Location 1 Location 2 Location 3 mm ->l J-J 5/20 5/25 30 5/30 76 6/5 6/10 102 8 6/15 41 6/20 6 8 6/25 23 25 76 6/30 101 7/5 25 84 89 7/10 L3 7/15 7/20 102 7/25 20 25 7 6 7/30 iy L8 8/5 33 38 8/10 8/15 18 8/20 76 127 51 8/25 8/30 9/5 127 10 9/10

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36 were analyzed, interactions occurred among N rates and locations, so locations were analyzed separately. Several reports indicate that source-sink relationships affect the accumulation of N. Grain, residue, and whole plant DM yield increased to 56 kg N ha ^ at locations 1 and 3 which was probably due to insufficient rainfall during the silking to ear fill period (Table 2-4) Grain yield decreased with increasing rate of N at location 1 where rainfall was limited. This physiological response of corn to drought stress has been reported previously by Shimshi (1969). Corn grain yield increased at locations 1 and 3 in response to 56 kg N ha 1 and to 112 kg N ha at location 2 (Table 2-4) Grain yields averaged over the three locations ranged from 250 kg ha at the zero rate to 2270 kg ha 1 at the 224 kg N ha 1 rate. The corn grain to residue ratio reacted differently to N rate at each location and increased to 56, 112, and 168 kg N ha 1 at locations 1, 2, and 3, respectively. Corn grain to residue ratio averaged over the three locations showed a 250% increase from 0 to 224 kg N ha \ Anderson et al. (1985) stated that the response of corn to increase N fertility differs considerably due to genotype, climatic, and other environmental conditions. Some hybrids show increases in protein content and/or grain yield as N rates increase (Kamprath et al., 1973; Nelson, 1956). Balko and Russell (1980) reported that some corn inbreds showed no response while others showed linear or quadratic yield responses to increased fertility. Dry matter yield for corn residue and whole plant increased up to 168 kg N ha 1 at location 2 (Table 2-4) The number of ears ha ^ increased in response to 56 kg N ha ^ at locations 1 and 2; however,

PAGE 44

37 Table 2-4. Tropical corn yield response to rates of anhydrous ammonia. Location N Treatment — Average 12 3 kg N ha Grain yield Mg DM ha 0 .24 .24 .26 .25 56 1.17 1.48 1.76 1.47 112 1.08 2.69 2.24 2.00 168 1.12 3.25 2.22 2.20 224 .68 3/58 2.54 2.27 LSD 0.05 .42 .86 .58 Residue Mg DM ha ^ 0 1.55 1.12 1.18 1.32 56 2.62 2.97 2.82 2.80 112 2.72 3.29 3.50 3.17 168 3.14 4.30 3.46 3.63 224 2.64 4.31 4.23 3.73 LSD 0.05 .75 .98 .82 Whole plant Mg DM ha 1 0 1.79 1.35 1.54 1.56 56 3.79 4.45 4.58 4.27 112 3.80 5.97 5.74 5.17 168 4.25 7.54 5.69 5.83 224 3.32 7.88 6.77 5.99 LSD 0.05 1.02 1.57 1.23 Grain/residue 0 .15 .19 .24 .19 56 .45 .52 .61 .53 112 .38 .77 .64 .60 168 .36 .82 .68 .62 224 .27 .83 .62 .37 LSD 0.05 .15 .23 .14

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38 the number of ears increased to 224 kg N ha at location 3 (Table 2-5). The ear number also decreased with increasing rate of N at location 1. The decreased ear number would indicate a source-sink physiological problem as well as more barren plants at this location. There were no differences in the number of plants ha ^ at locations 1 and 2; however, location 3 did show significant differences to varying rates of N. The number of ears/stalk responded to 56 kg N ha at all three locations. The shelling percent of corn grain was similar at locations 1 and 3, but was significantly lower at location 2 and responded to 56 kg N ha Almost every plant process is affected directly or indirectly by water deficits. When plants are subjected to water stress there is a decrease in photosynthesis and cell enlargement. There is also considerable retention of carbohydrates in photosynthetic tissue. Although translocation proceeds, its rate is reduced. It is generally accepted that optimized grain filling requires continued DM production and translocation of the product to the grain. Hanway (1962a) reported that the potential yield of corn grain which is produced late in the season is determined by the leaf area, which is produced early in the season. However, less than this potential yield of grain will actually be attained if (a) the net assimilartion rate is decreased by any factor such as a moisture deficiency later in the season or (b) the leaf area is prematurely reduced by some factor that results in premature death of leaves such as a nutrient deficiency or insect, disease, or hail damage. If no other factor limits yield, one would expect that

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39 Table 2-5. Response of tropical corn agronomic variables to rates of anhydrous ammonia. Location N Treatment Average 12 3 kg N ha Plants ha 0 44,470 48,420 22,420 38,440 56 39,450 52,290 27,260 39,840 112 39,450 54,150 30,490 41,360 168 37,660 54,870 25,460 39,810 224 39,450 55,230 30,130 41,600 LSD 0.05 NS* NS 4,650 Ears ha ^ 0 13,630 27,970 16,140 18,290 56 30,840 40,890 25,460 32,100 112 29,050 45,900 29,770 34,900 168 28,690 50,930 24,750 35,200 224 25,100 51,290 32,280 36,340 LSD 0.05 9,750 9,540 5,530 Ears/stalk 0 0.31 0.58 0.72 0.47 56 0.78 0.78 0.93 0.80 ll 2 0.74 0.85 0.97 0.84 168 0.76 0.93 0.97 0.88 224 0.64 0.93 1.07 0.87 LSD 0.05 0.22 0.25 0.23 Shelling percent 0 78 55 72 68 56 76 68 77 74 H 2 78 72 77 76 168 77 75 77 76 224 70 73 76 73 LSD 0.05 NS 5 NS NS = Not significant at the 0.05 level of probability.

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40 increasing leaf area index (LAI) up to the point where complete interruption of light occurs should result in increased grain yield. Moss (1962) and Allison and Watson (1966) have shown that when the corn grain sink is missing, DM that would have been translocated to the grain accumulates in the stem and husk. Goldsworthy and Colegrove (1974) have shown that the presence of more barren plants probably explains why more dry weight accumulated in the stems of corn plants. Missing grain sink would also account for the differences in the values for grain yield during the current study, since barren plants contribute to DM but not to grain yield. Jurgens et al. (1978) in a water stress experiment showed that as grain development progressed, the rate of grain fill began to exceed DM accumulation, indicating a net redistribution of stored assimilates. Eck (1984) stated that N fertilizer increases water-use efficiency of N deficient soils when water is adequate but less is known of the effects of high rates of N when water is limiting. Bandel et al. (1975) demonstrated decreased DM yields of corn from N rates in excess of 200 kg N ha 1 on low water level treatments. Denmead and Shaw (1960) indicated that moisture stress prior to silking reduced grain yield by 25%, moisture stress at silking reduced grain yield by 50%, and stress after silking reduced grain yield by 21%. Utilizing contrast statements for orthogonal polynomials, stalk DM yield showed a linear response to N rate at all three locations (Table 2-6). However, grain DM yield, whole plant DM yield, and the grain to stover ratio showed quadratic responses to N at location 1 but linear at locations 2 and 3.

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41 Table 2-6. Regression of responses of tropical corn on rate of nitrogen applied as anhydrous ammonia. Dependent Variable Regression Equation Location 1 Grain yield kg ha Stalk yield kg ha Whole pland yield kg ha~l Grain/stover N cone, grain dag kg -'-1 -1 N content grain kg ha N cone, stalks dag kg" N content stalks kg ha ^ DOM grain kg ha~l 1V0MD stalks dag kg DOM stalks kg ha _1 -1 Y Y Y Y Y Y Y Y Y Y Y -691 1723 1196X 270X -378 + 2675X -.09 + .33X I. 24 + .10X II. 17 + .19X .46 + .08X 7.6 + 3.5X 575 + 5.7X 43.8 + 1.86X 733 + 175X 185X 378X' .05X 2 2* 0.52 0.25 0.36 0.36 0.53 0.60 0.46 0.46 0.60 0.49 0.37 Location 2 -1 -1 Grain yield kg ha Stalk yield kg ha Whole plant yield kg ha Grain/stover -1 .-1 N cone, grain dag kg N content grain kg ha" N cone, stalks dag kg -*N content stalks kg ha -'IVOMD grain dag kg -1 -1 DOM grain kg ha IVOMD stalks dag kg DOM stalks kg ha" 1 -1 Y = -290 + 884X Y = 882 + 771X Y = 592 + 1616X Y = .17 + .15X Y = 1.35 + .04X Y = -5.2 + 12. 7X Y = 3.45 + 4.6X Y = 580 + 10. 2X Y = 53 8.5X + 1.2X' Y = 386 + 302X 0.72 0.59 0.70 0.52 0.14 0.75 NS** 0.62 NS 0.40 0.51 0.59

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42 Table 2-6. Continued Dependent Variable Regression Equation Location 3 Grain yield kg ha Stalk yield kg ha -1 Whole plant yield kg ha Grain/stover ^ N cone, grain dag kg N content grain kg ha "' N cone, stalks dag kg~l N content stalks kg ha "' IVOMD grain dag ha -*DOM grain kg ha l IVOMD stalks dag kg~ DOM stalks kg ha _1 -1 = 297 + 502X = 1098 + 654X = 1396 + 1156X .31 + .59 + -2.7 + .'37 + 08X 19X 8.6X 08X = .98 + 6.04X 0.55 0.48 0.55 0.35 0.76 0.70 0.49 0.66 *X = Coded N rate; X = 1-5, 1=0, 2 = 56, 3 = 112, 4 = 168, and 5 = 224 kg N ha -1 ** NS = Not significant at the 0.05 level of probability.

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43 The concentration of N in corn grain increased in response to 112 kg N ha" 1 at location 2, to 168 kg N ha 1 at location 3, and to 224 kg N ha" 1 at location 1 (Table 2-7). At location 1 there was an increased concentration of N as N rate increased. The concentration of P and K increased in response to 224 kg N ha 1 and 56 kg N ha ^ rates, respectively, at location 2 (Table 2-7). Nitrogen fertilizer did not affect the concentration of Ca, Mg, Fe, Mn, Cu, or Zn at locations 1 and 3. However, at location 2, 168 kg N ha 1 fertilizer caused Ca to increase and the 112 kg N ha _1 rate caused Mg to increase in concentration (Table 2-7) Since location 2 had a better rainfall distribution, an increased uptake of nutrients should have occurred providing higher concentrations of elements in the grain. The concentration of N in corn stalks increased up to the 224 kg N ha _1 rate at location 1 and up to the 168 kg N ha 1 rate at locations 2 and 3 (Table 2-8) Regression equations for stalk N concentrations versus rate of N application are given in Table 2-6. Correlations were low for N concentration in stalks when compared with N rates. Phosphorus, K, Mg, Fe, or Mn concentrations in stalks were not affected by rate of N (Table 2-8). Calcium concentration increased in response to 56 kg N ha _1 at location 1 and to 168 kg N ha 1 at location 3. Zinc was highest in the control plots and did not respond to N application. The content of N in corn grain increased in response to 56 kg N ha" 1 at location 1 and to the 112 kg N ha 1 rate at locations 2 and 3 (Table 2-9). Rhoads and Stanley (1981) stated that the amount of grain produced for each kg of N contained in the aerial portion of corn plants ranges from 30 to 60 kg. In the current study, grain yield per kg N in the plant ranged from 25 to 44 kg for 0 to 56 kg N ha applied.

PAGE 51

44 Table 2-7. Response of tropical corn grain nutrient concentration to rates of anhydrous ammonia. Location N Treatment — Average 12 3 kg N ha N dag kg 0 1.30 1.40 0.80 1.20 56 1.50 1.30 1.00 1.30 112 1.60 1..50 1.20 1.40 168 1.60 1.50 1.40 1.50 224 1.80 1.50 1.50 1.60 LSD 0.05 0.18 0.13 0.18 p dag kg 1 0 0.22 0.34 0.34 0.30 56 0.30 0.38 0.35 0.34 112 0.30 0.45 0.36 0.37 168 0.29 0.44 0.37 0.37 224 0.25 0.53 0.39 0.39 LSD 0.05 NS* 0.08 NS K dag kg 1 0 0.38 0.48 0.42 0.43 56 0.39 0.51 0.40 0.43 112 0.44 0.54 0.40 0.46 168 0.46 0.53 0.39 0.46 224 0.41 0.54 0.40 0.45 LSD 0.05 NS 0.03 NS

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45 Table 2-7. Continued Location N Treatment Average 12 3 kg N ha Ca dag kg 0 5 12 7 8 56 5 7 8 7 112 4 13 8 8 168 5 15 13 11 224 5 12 13 10 LSD 0.05 NS 2 NS Mg dag kg 1 0 0.11 0.18 0.11 0.13 56 0.12 0.18 0.11 0.14 112 0.13 0.23 0.13 0.16 168 0.15 0.22 0.13 0.17 224 0.12 0.23 0.13 0.16 LSD 0.05 NS 0.03 NS Fe mg ha 0 30 47 53 43 56 32 47 43 41 112 30 55 73 53 168 35 63 83 60 224 33 62 68 54 LSD 0.05 NS NS NS

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46 Table 2-7. Continued Location N Treatment Average 12 3 kg N ha : Mn mg ha 0 3.0 7.0 5.0 5.0 56 5.0 8.0 6.0 6.0 112 5.0 8.0 7.0 7.0 168 5.0 9,0 7.0 7.0 224 5.0 9.'0 7.0 7.0 LSD 0.05 NS NS NS Cu mg ha ^ 0 3.0 2.7 1.3 2.0 56 2.0 2.0 1.3 1.8 112 2.0 2.3 1.3 1.9 168 3.0 2.0 1.0 1.9 224 2.7 2.3 1.0 2.0 LSD 0.05 NS NS NS Zn mg ha ^ 0 22 50 31 34 56 18 59 31 36 112 18 60 31 36 168 19 59 25 34 224 23 57 27 36 LSD 0.05 NS NS NS NS = Not significant at the 0.05 level of probability.

PAGE 54

47 Table 2-8. Response of nutrient concentration in tropical corn stalks to ratio of anhydrous ammonia. Location N Treatment Average 12 3 kg N ha N dag kg 0 0.47 0.58 0.48 0.51 56 0.64 0.46 0.50 0.53 112 0.84 0.55 0.56 0.70 168 0.73 0.59 0.76 0.69 224 0.82 0.55 0.74 0.70 LSD 0.05 0.13 0.07 0.15 P dag kg 1 0 0.20 0.31 0.24 0.25 56 0.21 0.23 0.18 0.21 112 0.22 0.20 0.14 0.19 168 0.20 0.21 0.15 0.19 224 0.25 0.20 0.18 0.21 LSD 0.05 NS* NS 0.03 K dag kg 1 0 0.90 1.20 1.00 1.00 56 0.90 1.10 1.10 1.00 112 1.10 1.20 1.10 1.10 168 0.90 1.20 1.10 1.10 224 0.90 1.00 1.00 1.00 LSD 0.05 NS NS NS

PAGE 55

48 Table 2-8. Continued Location N Treatment — Average 12 3 kg N ha Ca dag kg 0 0.14 0.19 0.20 0.18 56 0.24 0.17 0.23 0.21 112 0.21 0.20 0.30 0.24 168 0.20 0.22 0.38 0.27 224 0.19 0.19 0.31 0.23 LSD 0.05 0.03 NS 0.07 Mg dag kg 1 0 0.26 0.25 0.18 0.23 56 0.30 0.26 0.17 0.24 112 0.30 0.25 0.18 0.24 168 0.28 0.25 0.26 0.24 224 0.26 0.22 0.19 0.22 LSD 0.05 NS NS NS Fe rag kg ^ 0 60 70 70 70 56 60 80 60 70 112 70 70 70 70 168 60 80 70 70 224 80 70 80 70 LSD 0.05 NS NS NS

PAGE 56

49 Table 2-8. Continued Location N Treatment Average 12 3 kg N ha r Mn mg kg 0 20 20 20 20 56 20 30 40 30 112 20 20 40 30 168 20 30 50 30 224 20 30 40 30 LSD 0.05 NS NS NS Cu mg kg 1 0 3.0 2.8 2.0 2.6 56 3.3 2.8 2.5 2.8 112 4.5 4.0 3.2 3.9 168 3.5 4.0 4.0 3.8 224 3.6 4.3 3.0 3.6 LSD 0.05 NS 0.8 0.7 Zn mg kg ^ 0 20 50 30 30 56 10 30 20 20 112 10 20 10 20 168 10 20 10 20 224 10 20 10 10 LSD 0.05 3 9 8 NS = Not significant at the 0.05 level of probability.

PAGE 57

Table 2-9. Response of nutrient content in tropical corn grain to rates of anhydrous ammonia. Location N Treatment — Average 12 3 kg N ha N kg ha 0 3 3 2 3 56 17 20 18 18 112 17 4Q 27 28 168 18 49 31 33 224 12 53 38 34 LSD 0.05 6 12 9 P kg ha _1 0 1.0 1.0 1.0 7.0 56 3.0 6.0 7.0 5.0 112 3.0 12.0 8.0 8.0 168 3.0 14.0 9.0 9.0 224 2.0 19.0 10.0 10.0 LSD 0.05 1.0 4.0 3.0 0 1.0 1.0 1.0 1.0 56 5.0 8.0 7.0 2.0 112 5.0 14.0 9.0 9.0 168 5.0 17.0 9.0 10.0 224 3.0 19.0 10.0 LSD 0.05 2.0 5.0 3.0

PAGE 58

Table 2-9. Continued Location N Treatment Average 12 3 kg N ha • Ca kg ha 0 0.01 0.03 0.02 0.02 56 0.06 0.12 0.14 0.10 112 0.03 0.34 0.17 0.18 168 0.05 0.48 0.30 0.22 224 0.03 0.43 0.35 0.29 LSD 0.05 0.02 0.13 0.16 Mg kg ha ^ 0 0.3 0.4 0.3 0.3 56 1.4 2.8 1.9 2.0 112 1.4 6.2 2.8 3.4 168 1.6 7.0 3.0 3.9 224 0.8 8.3 3.3 4.1 LSD 0.05 0.6 2.1 1.1 Fe g ha 0 7 1 2 12 56 4 7 8 6 112 3 15 16 11 168 4 20 19 14 224 2 22 18 20 LSD 0.05 1 7 7

PAGE 59

r )2 Table 2-9. Continued Location N Treatment Average 12 3 kg N ha Mn g ha 0 0.09 0.1 0.1 0.10 56 0.50 1.0 1.0 0.80 112 0.50 2.0 2.0 1.50 168 0.60 2..0 2.0 1.50 224 0.30 3.0 2.0 1.80 LSD 0.05 0.10 0.6 1.0 Cu g ha 0 0.60 0.06 0.04 0.05 56 0.20 0.30 0.20 0.20 112 0.20 0.60 0.30 0.40 168 0.30 0.70 0.20 0.40 224 0.20 0.80 0.20 0.04 LSD 0.05 0.10 0.10 0.10 Zn g ha ^ 0 0.5 1.0 0.8 3.0 56 2.0 9.0 6.0 6.0 112 2.0 20.0 7.0 10.0 168 2.0 20.0 6.0 9.0 224 1.5 20.0 7.0 10.0 LSD 0.05 0.6 5.0 2.0

PAGE 60

53 The N content of corn stalks responded in the same way as for grain (Table 2-10) Phosphorus content of stalks responded similarly at all locations and increased with an application of 56 kg N ha Potassium, Ca, Mg, and Mn contents all increased in response to the 56 kg N ha ^ rate at locations 2 and 3. At location 1, Ca and Cu contents increased to rates of 56 and 112 kg N ha respectively. There was no significant response to N rate of other nutrients at location 1 (Table 2-10). Colliver and Welch (1970) found that P uptake may be restricted by application of anhydrous ammonia. Fribourg et al. (1976) stated that the content of N, P, K, Ca, and Mg exhibits considerable variability. This was not unexpected since soil drainage, fertility, climatic conditions, and fertilizer practice can influence yield levels and crop content of each element. Hanway (1962b) reported that the mineral nutrition of corn plants in the field appears to influence grain yields mainly by affecting the leaf area produced early in the season, and the length of time the leaves remain alive and functioning during grain formation. Yamaguchi (1974) found in a study of tropical corn that leaves die quickly after silking and the duration from silking to harvest is short, hence leaf area duration (LAD) is smaller. The reason for this is unknown, but it seems that high temperature is one of the important factors since senescence is slow when temperatures are cooler. Nair and Babu (1975) stated that Zn-P-Fe interactions occurred in the corn plant. Higher P levels reduced Zn concentration in the shoots by more than half as compared to roots. The mobility of Zn and Fe was impeded from root to shoot in their study. In vitro organic matter digestibility increased only in corn stalks at locations 1 and 2; however, digestible organic matter (DOM)

PAGE 61

3a Table 2-10. Response of nutrient content in tropical corn stalks to rates of anhydrous ammonia. Location N Treatment Average 12 3 kg N ha N kg ha 0 7 7 6 7 56 17 13 14 15 112 23 18 19 20 168 23 25 19 24 224 22 24 31 26 LSD 0.05 6 6 7 p kg ha -l 0 3.0 3.5 3.1 3.2 56 5.4 6.5 4.9 5.6 112 5.7 6.2 4.7 5.5 168 6.2 9.1 5.3 6.8 224 6.4 8.6 7.5 7.5 LSD 0.05 1.8 2.5 1.4 K kg ha _1 0 15 14 13 14 56 25 33 30 29 112 30 39 37 35 168 29 50 36 38 224 24 46 40 37 LSD 0.05 9 13 11

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55 Table 2-10. Continued Location N Treatment Average 12 3 kg N ha Ca kg ha 0 2.0 2.0 2.6 2.2 56 6.4 4.8 6.4 5.9 112 5.6 6.0 10.4 7.5 168 6.4 9.3 12.4 9.2 224 5.0 7.9 12.6 8.5 LSD 0.05 1.7 2.4 3.2 Mg kg ha ^ 0 4.1 2.8 2.3 3.0 56 7.9 7.4 4.7 6.7 112 8.1 8.1 6.2 7.4 168 8.7 10.9 6.9 8.9 224 6.3 9.4 7.9 7.9 LSD 0.05 NS* 2.9 1.6 Ye g ha ^ 0 9 8 9 8 56 17 22 17 19 112 19 23 24 22 168 21 33 26 26 224 22 29 32 27 LSD 0.05 NS 9 8

PAGE 63

5h Table 2-10. Continued Location N Treatment — — — Average 12 3 kg N ha Mn g ha 0 3 2 5 3 56 5 7 12 8 112 7 8 15 10 168 7 12 16 11 224 7 11 17 11 LSD 0.05 NS 4 5 Cu g ha ^ 0 0.4 0.3 0.3 0.3 56 0.9 0.8 0.7 0.8 112 1.2 1.3 1.1 1.2 168 1.1 1.7 1.4 1.4 224 1.0 1.9 1.2 1.4 LSD 0.05 0.1 0.1 0.1 Zn g ha ^ 0 3 6 4 4 56 2 8 6 5 112 4 8 5 6 168 3 9 5 6 224 3 8 7 6 LSD 0.05 NS 3 3 NS = Not significant at the 0.05 level of probability.

PAGE 64

57 content of grain and stalks increased in response to 56 to 168 kg N ha 1 (Table 2-11). There was a linear increase for DOM in stalks at both locations and a quadratic increase for IVOMD concentration at location 2 (Table 2-6) The IVOMD of corn grain was 60% greater than for stalks when averaged over all locations and rates. This could be due to a dilution effect since DOM ha 1 was greater in stalks than in grain. Monson et al. (1980) in comparing tropical corn with temperate found no difference in whole plant in vitro dry matter digestibility (IVDMD) at final harvest, 73% vs 72.1%. Correlation coefficients for yield, agronomic variables, nutrient concentration, and nutrient content are found in Appendix Tables A-2 through A-19. Analysis of the youngest mature leaf at 40 days after emergence indicated that N concentration was increased by application of 56 to 224 kg N ha" 1 (Table 2-12). The only other nutrient that was affected by N fertilizer was Fe which increased to 168 kg N ha \ When the whole plant was sampled at 40 days after emergence, there was a change in plant concentration of N, Ca, Mg, Fe, Mn, and Ca to N rates of 112, 56, 56, 56, 112, and 112 kg N ha" 1 respectively (Table 2-13). When the ear leaf was sampled at the bloom stage of maturity, fertilizer N only affected OM and IVOMD at 224 and 56 kg N ha \ respectively, when averaged over the two locations (Table 2-14). Nitrogen values ranged from 1.87 to 2.78 dag kg 1 at 40 days post emergence for youngest mature leaf, 1.61 to 2.78 dag kg 1 for the whole plant at 40 days, and 1.66 to 2.43 dag kg" 1 for the ear leaf at bloom (Tables 2-12 to 2-14). Critical nutrient levels (CNL) for corn were first established by Tyner (1946). He proposed CNL levels of 2.9 dag kg -1 N, 0.29 dag kg" 1 P, and 1.3 dag kg 1 K for the sixth leaf at silking. Since then many CNL

PAGE 65

3 8 Table 2-11. Response of tropical corn grain and stalk organic matter to rates of anhydrous ammonia. Location Average N Treatment 1 2 Grain Stalk Grain Stalk Grain Stalk kg N ha OM dag kg 0 99.4 96.2 99.0 97.0 99.2 96.6 56 99.5 95.7 98.8 97.2 99.2 96.5 112 99.2 95.7 98.8 96.9 99.0 96.3 168 98.3 95.0 98.8 97.0 98.6 96.0 LSD 0.05 0.5 0.5 NS* NS OM Mg ha" 1 0 0.24 1.49 0.23 1.08 0.23 1.29 56 1.16 2.51 1.46 2.89 1.31 2.70 112 1.07 2.60 2.65 3.19 1.86 2.89 168 1.10 2.98 3.21 4.17 2.15 3.57 224 0.67 2.49 3.53 4.20 1.43 3.35 LSD 0.05 0.42 0.71 0.85 0.96 IVOMD dag kg" 1 0 74.0 45.2 77.9 46.0 76.0 45.6 56 71.8 48.3 76.0 40.8 74.0 44.6 112 74.9 49.5 74.5 38.5 74.7 44.0 168 76.1 50.5 71.6 39.6 76.1 45.1 224 77.6 53.4 70.6 41.5 74.1 47.5 LSD 0.05 NS 3.7 NS 3.4 DOM Mg ha" 1 0 0.18 0.69 0.14 0.52 0.16 0.61 56 0.84 1.27 0.82 1.20 0.83 1.24 112 0.82 1.34 1.47 1.26 1.15 1.28 168 0.84 1.59 1.85 1.71 1.35 1.65 224 0.51 1.41 1.79 1.77 1.15 1.60 LSD 0.05 0.32 0.36 0.53 0.41 NS = Not significant at the 0.05 level of probability.

PAGE 66

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PAGE 67

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64 Q S O > s o a u -a a a (3 u u 5 I CM H 1 cn o o c 1 r~r o vt CM c rH cn m m o 1 >£> vO •H u n) o 00 r~, iO m rn o 1 en 00 O CM CM hJ pH O 3> ON ON r rH vD iO c u E 4-1 a) H in m rn 1 t— i CN m m CM c m H 4-J CO CJ 1 o o DO CO DO O 1 c~— — pJ rH 1 • O rCM in 1 ON ON ON ON ON 1 m m o m 1 CM CM m CM CM d m i", o I cn cn CM CM CM •H 4-1 CO O m o o m in O 1 r~ in >-J H o o CC rn m --r P 00 in — nD CM CO i — < —1 CM rJ

PAGE 72

65 values or ranges of values have been proposed, but the consensus of the literature places CNL levels at approximately 2.75 to 3.50 dag kg for N, 0.25 to 0.40 dag kg" 1 for P, and 1.5 to 2.5 dag kg -1 for K, when measured in the ear leaf at silking. In the current study, no rate of N gave these levels of N in the ear leaf when sampled. Phosphorus tended to decrease with increasing rate of N, and only the control and 56 kg N ha ^ would meet CNL requirements for P. Potassium met or exceeded the CNL requirement (Table 2-14) Correlation coefficients for nutrient concentration used to predict grain, stalk, and whole plant DM yields by three sampling methods are found in Table 2-15. When the youngest mature leaf was sampled at 40 days post emergence there was a high positive correlation between N and Ca concentration in the leaf with final grain, stalk, and whole plant DM yield. Potassium was negatively correlated to grain yield. Zinc was also negatively correlated but to stalk and whole plant yield as well as grain yield. Phosphorus, Mg, Fe, Mn, Cu, DM, OM, and IVOMD were not well correlated with grain, stalk, and whole plant yield at either locations utilizing this sampling technique. Calcium and N were well correlated with final yield but neither nutrient met sufficiency levels in this study. At this stage of growth N concentration should range from 3.5 to 5 dag kg ^ and Ca from 0.300.70 dag kg Nitrogen and Ca concentration in the youngest mature leaf did not meet the above mentioned levels at any rate of applied N (Table 2-12). When the whole plant was sampled at 40 days post emergence more nutrients were correlated with final grain, stalk, and whole plant DM yields (Table 2-15) Nitrogen and Ca were again positively correlated

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66 Table 2-15. Correlation coefficients between plant characteristics and grain, stalk, and whole plant dry matter yield for tropical corn at two locations. Youngest mature leaf at 40 days Whole plant at 40 days Ear leaf at silking Location Location Location 1 2 1 2 1 2 -1 dag kg i -1 gram kg ha N 0.69 0.64 0.69 0.74 0.71 0.79 P -0.65 NS* NS NS NS NS K -0.52 -0.47 -0.56 -0.44 NS NS Ca 0. 69 0.42 0.76 0.66 0.54 0.43 Mg 0.57 NS 0.52 0.53 NS NS Fe NS 0.39 NS NS 0.43 -0.43 Mn NS NS NS NS NS NS Cu NS NS 0.44 0.68 NS NS Zn -0.42 -0.56 NS NS -0.61 -0.41 DM NS -0.41 NS -0.46 -0.55 NS OM NS NS NS -0 39 NS NS IVOMD NS 0.38 NS -0.53 stalks kg ha ^ — 0.73 NS N 0.70 0.57 0.50 0.50 0.57 0.57 P -0.52 NS 0.40 NS NS NS K NS -0.38 -0.60 -0.40 NS NS Ca 0.58 0.43 0.77 0.68 0.45 0.48 Mg 0.46 NS 0.67 0.65 NS NS Fe NS NS 0.39 0.40 0.40 NS Mn 0.49 NS 0.49 0.39 NS NS Cu NS NS 0.44 0.47 NS NS Zn -0.51 -0.50 NS NS -0.62 NS DM NS -0.47 NS -0.53 -0.66 NS OM NS NS NS NS 0.38 NS IVOMD NS 0.43 0.39 -0.65 0.69 0.43

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Table 2-15. Continued 67 Youngest mature leaf at 40 days Location Whole plant at 40 days Location Ear leaf at silking Location whole plant kg ha N P K Ca Mg Fe Mn Cu Zn DM OM IVOMD 0.73 0.63 0.49 0.65 0.66 -0.60 NS NS NS NS NS -0.45 -0.62 -0.44 NS 0.65 0.45 0.81 0.71 0.45 0.53 NS 0.66 0.62 NS NS NS 0.40 NS 0.44 0.37 NS 0.38 NS NS NS NS 0.46 0.60 NS -0.50 -0.56 NS NS -0.65 NS -0.46 NS -0.52 -0.66 NS NS NS NS NS xs 0.43 NS 0.62 0.75 0.71 NS NS 0.48 NS 0.40 NS NS NS NS NS 0.40 NS = Not significant at the 0.05 level of probability,

PAGE 75

68 with grain, stalk, and whole plant DM yields with K being negatively correlated. However, Cu and Mg were also positively correlated with final DM yields. When the ear leaf was sampled at mid-silking, only N, Ca, and Zn were well correlated at both locations to predict grain yield. Nitrogen and Ca concentrations in the leaf were positively correlated while Zn was negatively correlated. Nitrogen, Ca, and IVOMD were positively correlated to stalk and whole plant DM yield. The reason for the IVOMD being correlated to yields of stalk and whole plant is that the IVOMD of grain does not vary much but is directly influenced by moisture availability, DM accumulation, source-sink, and nutrient uptake in the vegetative portions of the plant. Bennett et al. (1973) noted grain yield increases with increasing N and P levels in the ear leaf. Gallaher et al. (1972) found that in corn, seasonal variation in rainfall, temperature, and sunlight caused large differences in yield and ear leaf concentration of K. Hanway (1962c) reported that several researchers have found high positive correlations between the percentages of N, P, and K in corn leaves at silking time and the yield of grain. Conclusions Grain, residue, and whole plant DM showed a positive response to the 56 kg N ha 1 rate at two locations. At the third location, a significant increase for the yield parameters occurred in response to the 112 kg N ha 1 rate. There was a 250% increase for the corn grain to residue ratio over the control. Insufficient rainfall during the silking through ear fill period decreased grain yields more than

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69 residue yields. Also, grain yields were more depressed when the highest rate of N (224 kg ha ) was applied at location 1. Grain, stalk, and whole plant DM yields increased linearly at locations 2 and 3, but increased quadratically at location 1 for grain and whole plant DM yield due to moisture stress. The concentration of nutrients varied with N fertilizer rate at each location. Nitrogen content increased linearly at all locations. Total grain yield per kg of N content ranged from 25 ro 44 kg ha The N content of stalks responded the same as grain. The concentration and content of most other nutrients did not respond to N rate at any location or only increased in response to the 56 kg N ha ^ rate. The analysis of diagnostic samples indicated that N and Fe were the only elements increased by N rate when youngest mature leaves were sampled at 40 days post emergence. Whole plant samples at 40 days exhibited a change in nutrient concentration for N, Ca, Mg, Fe, Mn, and Cu. Ear leaf sampled at mid-silk showed an increase to N rate for OM and IVOMD. The concentration of N and P were lower than the CNL values recommended by Tyner (1946) for sufficiency levels in corn ear leaves. Only K met the CNL values recommended by various researchers. Nutrient concentration by three sampling methods as predictors of grain yield indicate that N, Ca, and Zn were all well correlated with grain, stalk, and whole plant DM yield when the youngest mature leaf at 40 days was utilized. When the whole plant at 40 days post emergence was sampled, N and Ca were positively correlated to final yields with K being negatively correlated. Copper and Mg were also positively correlated with final DM yields when this sampling technique was utilized. When the ear leaf at silking was sampled, N and Ca were positively

PAGE 77

70 correlated and Zn negatively correlated with grain yield. Nitrogen, Ca, and IVOMD were positively correlated to stalk and whole plant DM yield

PAGE 78

CHAPTER 3 ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR GRAIN SORGHUM PLANTED INTO BAHIAGRASS SOD BY MINIMUM TILLAGE METHODS Introduction Grain sorghum ( Sorghum bicolor L. Moench) is gaining popularity in the Southeast as a feed grain. It has been studied in multicropping systems (Nelson et al., 1977a) and fits well into a combine type farming operation. Date of planting is not as limiting and yield increase from close row spacing is greater than from corn ( Zea mays I.) or soybeans ( Glycine max L. Merrill) (Larson and Maranville, 1977). Under some conditions higher grain yields have been produced with grain sorghum than with corn (Lutrick, 1978) Vast areas in the Southeast are occupied by perennial sods which could be more fully utilized if interplant multicropping minimum tillage systems were feasible. Multicropping systems utilizing bahiagrass ( Paspaluin no ta turn L. Flugge) sod followed by grain sorghum have been studied (Lundy et al. 197A; Prine and Robertson, 1968; Robertson et al. 1976). However, only a few of these studies involved in-row subsoiling and none utilized anhydrous ammonia as the sole source of N. Grain sorghum has high yield potential (Smith, 1966) and produces grain which can be increased appreciably in protein content. Magnitude of grain sorghum response to N f erti] izer addition is indicated by findings of Miller et al. (1964) and Nelson (1952). Grain sorghum 71

PAGE 79

72 generally responds to N application similar to corn. However, yield is not so easily depressed as that of corn when N deficiency exists. The crop has a tendency to produce appreciable grain of very low protein content when corn would likely produce a very low yield. Grain sorghum tends to give less yield increase for a given application of N than corn which may be due in part to its ability to recover more available N from the soil. This behavior may be due to its ability when under stress to delay maturity allowing for more uptake of N from the soil. The level of N to which grain sorghum will respond varies considerably with environmental factors, soil type, fertilizer application rate, and climatic conditions (Lutrick, 1978) Johnson and Cummins (1967) reported that in Georgia 112 kg N ha ^ applied anytime up to 6 weeks after planting would give maximum yields of forage sorghum. Valentine and Onker (1968) observed a yield increase for irrigated grain sorghum up to 180 kg N ha ^ with the 135 kg N ha ^ rate giving the optimum response. They obtained an 8-year average grain yield increase of 1350 kg ha from the first 45 kg of N, 390 kg grain ha from the second 45 kg N, and225 kg grain ha~ from the third 45 kg N. Lutrick (1978) applied ammonium nitrate at rates of 0 to 188 kg N ha \ In general, the yield of grain sorghum did not increase significantly when more than 75 kg N ha ^ was applied on a yearly basis. The protein concentration increased in the grain of sorghum for increments of N up to and including 112 kg ha He then deduced that the recommended rate of applied N for grain sorghum should be 112 kg ha No-tillage planting a summer crop such as grain sorghum into a grass sod could hlep control erosion problems due to wind or water. Therefore, methods for chemically suppressing late spring and summer

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73 grass growth, but allowing for fall regrowth would be desirable. The renovation of the pasture sod with in-row subsoiling plus having grass regrowth and crop residues for livestock to graze in the Fall could dramatically increase the value and profitability of raulticropping sorghum with bahiagrass sods. The objective of this study was to determine the effect of anhydrous ammonia as the sole source of N in no-tillage plus subsoil planted sorghum into bahiagrass sod. Materials and Methods All materials and methods for this experiment were identical to those previously presented in Chapter 2 with only a few differences as discussed below. The grain sorghum experiment was conducted at three previously described locations during 1983 and 1984. The experiment was in a randomized complete block design with six replications utilizing DeKalb 'DK59' grain sorghum planted into 15-year-old bahiagrass (c.v. 'Pensacola') sods. All sorghum was planted at a population of 124,000 plants ha Two rows 6 m in length were hand harvested from each plot for yield determination. The samples were weighed and a five plant subsample taken for dry matter (DM) determination and chemical analyses. At 40 days post emergence five whole plants and five youngest mature leaves were collected from each plot to determine diagnostic potential of plant part sampling and analyses. At sorghum bloom, five leaves, each positioned three leaves down the stalk from the flag leaf, were collected from each plot for chemical analyses.

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74 All plants and plant parts were dried in a forced air oven at 70 C for 48 hours and weighed. Samples were prepared for further laboratory analysis by grinding in a Wiley mill to pass a 1 mm stainless steel screen and then stored in air-tight plastic bags. Planting dates, sampling, and harvest dates are listed in Table 3-1. Soil samples were taken following final harvest. Soil test results are shown in Appendix Table B-l. Results and Discussion Rainfall was limiting during the bloom to grain fill period, particularly at location 1 during 1983 (Table 3-2). As a result of interactions between N rate and locations, the data in this study were analyzed by location. Sivakumar et al. (1978) reported that the major components of sorghum yield which were significantly affected by drought in the case of non-irrigated plots were tertiary branches per secondaries, seed number per panicle, and seed size. The reduction in these components was 46, 26, and 28%, respectively, in their study. Their data point out the importance of the availability of a few additional cm of water to a sorghum crop under water stress and benefits that should accrue from such water application. Grain DM yield increased to the 56 kg N ha ^ rate at locations 1 and 2 and to the 112 kg N ha 1 rate at location 3 (Table 3-3). Residue yield increased at all three locations to the 112 kg N ha rate, while whole plant yield responded positively to the 56 kg N ha ^ rate at locations 1 and 3 and to the 112 kg N ha rate at location 2. Grain/residue, percent grain, and the number of plants ha ^ varied at each location and contributed to the variation of DM yields and

PAGE 82

75 — o a 00 oa to to n) o >j 4-1 ofl id a) — •H J2 DO c5 c ,13 •H 4-1 O DO 4-1 C > •H X) X CJ 4-1 ~3 3 c a) H a M 3 e •H 3 U JS c Ml CO >j i — 1 o M 00 c 0 o o C o -4 4-1 C5 o o c o r_ a o — ) CS to 13 c O 0> m CM CS cc ON 00 ON OA vC 00 CM CXI CS CO ON cr J3 oo u o •x M 0 14-1 e 00 x; cc ro 00 CJ H -i H IM •H o C/l (U E 3 H O ~j QJ 3 s-i c O 4-1 4-1 M-l a r fj 14-4 CO CO 4-1 CJ T3 B s 4-1 c cd CO o, o 00 4-1 H CJ s •H c TO Cc H (J (0 4-1 •H OJ to M CO 4-1 00 OJ 13 0) u c c H l-i > H OJ CO 3 O H •H a. H O A _C <0 O o CM >> 3 H CO i— 1 CS CO m

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76 Table 3-2. Rainfall data during 1983-84 at three locations where grain sorghum was planted into bahiagrass sod 1983 1984 Date Location 1 Location 2 Location 3 mm 5/1 j 5/20 5/25 30 5/30 76 6/5 6/10 102 S 6/15 41 6/20 6 8 6/25 23 25 76 6/30 101 7/5 25 84 S9 7/10 13 7/15 7/20 102 7/25 20 25 76 7/30 19 IS 8/5 33 38 8/10 8/15 18 8/20 76 127 51 8/25 8/30 9/5 127 10 9/10

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77 Table 3-3. Grain sorghum yield response to rates of anhydrous ammonia. Location N Treatment Average kg N ha ^ Grain yield Mg ha 1 0 0.51 0.20 0.51 0.41 56 1.92 0.77 1.87 1.52 112 1.86 1.08 2.83 1.92 168 2.22 1.48 3.14 2.28 224 2.50 1.38 1.88 1.92 LSD 0.05 0.60 0.48 0.62 Residue Mg ha ^ 0 1.58 2.08 0.69 1.45 56 2.96 4.64 2.14 3.25 112 3.65 5.86 3.02 4.16 168 3.85 5.76 2.99 4.20 224 4.30 6.41 2.32 4.34 LSD 0.05 0.54 1.21 0.52 Whole plant Mg ha ^ 0 2.10 2.30 1.20 1.90 56 4.92 5.37 3.97 4.72 112 5.56 6.88 5.83 6.10 168 6.12 7.28 6.14 6.48 224 6.80 7.78 4.18 6.22 LSD 0.05 0.90 1.50 1.00

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7 8 Table 3-3. Continued Location N Treatment Average 12 3 kg N ha 1 Grain/ residue 0 0.32 0.11 0.75 0.39 56 0.6A 0.17 0.89 0.57 112 0.51 0.19 0.95 0.55 168 0.58 0,25 1.05 0.63 224 0.60 0.21 0.84 0.55 LSD 0.05 0.18 0.06 NS* Grain dag kg ^ 0 24 9 41 24 56 39 14 47 33 112 34 17 48 33 168 36 20 51 36 224 37 17 45 33 LSD 0.05 10 5 10 Plants ha ^ 0 128,680 88,580 66,350 94,540 56 157,950 93,960 76,030 109,310 112 102,000 96,830 83,030 93,950 168 181,610 97,190 76,390 118,400 224 185,060 106,160 60,610 117,280 LSD 0.05 11,800 5,940 14,990 NS = Not significant at the 0.05 level of probability.

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79 interactions among locations and rates of N. Location 2 had severe sorghum webworm ( Celama sorghiella (Riley) (Lepidoptera:Noctuidae) ) infestation which contributed to lower grain yields and a lower grain to residue ratio than at the other two locations. Nitrogen concentration in sorghum grain ranged from 1.5 to 2.2 dag kg 1 when averaged over the three locations (Table 3-4). The response was to the 112 kg N ha rate at location 1 and to the 224 kg N ha" 1 rate at the other two locations. Phosphorus and Fe showed an increase to N rate at only location 1 which was to the 168 kg N ha" 1 (Table 3-4). Potassium, Ca, Mg, Mn, Cu, and Zn concentrations in grain were not affected by N fertilizer at any location. Nitrogen concentration of stalks increased to the 168 kg N ha" 1 rate at locations 1 and 3 and to the highest rate of 224 kg N ha _1 at location 2 (Table 3-5). Phosphorus reacted similarly at all locations and was highest in the control plots with no N applied. This response is due to dilution effect as more DM was accumulated at higher N rates. Also, it has been reported that NH^ may have an inhibitory effect on the uptake of P. Potassium increased to N fertility only at location 2 which was to 168 kg N ha Calcium and Mg stalk concentrations increased similarly to the 168 kg N ha" 1 Copper concentration of stalks varied and increased to the 224 and 168 kg N ha _1 rates at locations 1 and 3, respectively (Table 3-5). Zinc was highest in the control plots at only one location. Nutrient interactions in grain sorghum are not well documented but several studies have investigated particular ratios and interactions. More than half of the total nutrient uptake in the vegetative growth of

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8 0 Table 3-4. Response of grain sorghum grain nutrient concentration to rates of anhydrous ammonia. Location N Treatment Average 12 3 kg N ha N dag kg 0 1.61 1-68 1.15 1.48 56 1.67 1.52 1.14 1.44 112 1.99 1.7.8 1.34 1.70 168 2.17 1.95 1.53 1.89 224 2.34 2.41 1.90 2.22 LSD 0.05 0.25 0.42 0.17 P dag kg 1 0 0.26 0.44 0.40 0.37 56 0.23 0.32 0.37 0.31 112 0.28 0.34 0.42 0.35 168 0.36 0.32 0.47 0.38 224 0.32 0.36 0.40 0.36 LSD 0.05 NS* 0.10 NS K dag kg 1 0 0.44 0.55 0.48 0.49 56 0.45 0.55 0.42 0.47 112 0.49 0.55 0.47 0.50 168 0.45 0.57 0.50 0.51 224 0.41 0.52 0.40 0.44 LSD 0.05 NS NS NS

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81 Table 3-4. Continued Location N Treatment Average 12 3 kg N ha Ca dag kg 0 0.03 0.06 0.03 0.04 56 0.03 0.05 0.02 0.03 112 0.03 0.06 0.02 0.03 168 0.02 0.05 0.02 0.03 224 0.02 0.05 0.02 0.03 LSD 0.05 NS NS NS Mg dag kg 1 0 0.20 0.30 0.20 0.20 56 0.20 0.30 0.20 0.20 112 0.20 0.30 0.20 0.20 168 0.20 0.30 0.20 0.20 224 0.20 0.30 0.20 0.20 LSD 0.05 NS NS NS Fe mg kg 1 0 44 82 70 65 56 52 80 88 73 112 38 85 122 82 168 72 68 118 86 224 72 83 137 97 LSD 0.05 19 NS NS

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6 2 Table 3-4. Continued Location N Treatment — — — Average 12 3 kg N ha Mn mg kg 0 17 30 27 25 56 19 29 18 22 112 18 31 20 23 168 29 30. 24 27 224 19 36 21 25 LSD 0.05 NS NS NS Cu mg kg 1 0 4.2 6.3 2.8 4.4 56 3.6 5.7 2.7 4.0 112 4.0 7.0 2.8 4.6 168 4.8 7.2 3.3 5.1 224 4.4 6.7 3.0 4.7 LSD 0.05 NS NS NS Zn mg kg 1 0 20 38 28 29 56 18 34 25 26 112 22 37 27 29 168 24 37 28 30 224 20 35 25 27 LSD 0.05 NS NS NS NS = Not significant at the 0.05 level of probability.

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83 Table 3-5. Response of stalk nutrient concentration in grain sorghum to rates of anhydrous ammonia. Location N Treatment Average 12 3 kg N ha N dag kg 0 0.57 0.62 0.48 0.56 56 0.50 0.58 0.50 0.53 112 0.83 0.66 0.56 0.68 168 0.86 0.83 0.76 0.82 224 1.01 1.00 0.74 0.92 LSD 0.05 0.14 0.14 0.15 P kg ha -1 0 0.28 0.24 0.24 0.25 56 0.21 0.16 0.18 0.18 112 0.30 0.17 0.14 0.20 168 0.22 0.20 0.15 0.18 224 0.19 0.18 0.18 0.18 LSD 0.05 0.04 0.03 0.03 K kg ha _1 0 1.28 1.38 1.01 1.22 56 1.23 1.37 1.05 1.22 112 1.43 1.35 1.06 1.28 168 1.30 1.64 1.05 1.33 224 1.40 1.47 0.97 1.28 LSD 0.05 NS* 0.12 NS

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84 Table 3-5. Continued Location N Treatment Average 12 3 kg N ha Ca dag kg 0 0.14 0.16 0.20 0.17 56 0.18 0.18 0.23 0.20 112 0.18 0.17 0.30 0.22 168 0.20 0.17 0.38 0.25 224 0.19 0.18 0.31 0.23 LSD 0.05 0.02 NS 0.07 Mg d ag kg 1 0 0.20 0.21 0.18 0.20 56 0.24 0.22 0.17 0.21 112 0.27 0.25 0.18 0.23 168 0.27 0.26 0.20 0.24 224 0.29 0.22 0.19 0.23 LSD 0.05 0.03 0.03 NS Fe mg kg 1 0 74 112 72 86 56 84 135 62 94 112 88 118 68 91 168 82 75 73 77 224 102 77 77 85 LSD 0.05 NS NS NS

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8 5 Table 3-5. Continued Location N Treatment Average 12 3 kg N ha Mn mg kg 0 36 40 34 37 56 42 42 40 41 112 43 38 44 42 168 50 40 47 46 224 43 39 40 41 LSD 0.05 NS NS NS Cu mg kg 3.8 2.0 3.10 3.7 2.5 3.10 4.5 3.2 3.80 4.7 4.0 4.00 4.7 3.0 4.00 NS 0.66 Zn mg kg 31 29 26 27 20 20 25 14 18 25 15 19 25 15 19 NS 8 0 3.4 56 3.2 112 3.8 168 3.2 224 4.2 LSD 0.05 0.99 0 18 56 13 112 15 168 16 224 17 LSD 0.05 NS NS = Not significant at the 0.05 level of probability.

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86 grain sorghum occurs in early growth (Jacques et al., 1975). They observed that Cu and Zn were translocated from vegetative growth to the panicle as grain developed but that Mn was not. Nitrogen content of grain varied in response to 56, 112, and 168 kg N ha" 1 at locations 1 to 3 (Table 3-6). This response most likely relates to the source-sink differences among locations and the response of the plant to moisture stress. Phosphorus and K content also varied among locations and ranged from 1 to 10 and 2 to 11 kg ha respectively, in grain. Grain Ca content increased to the 56 kg N ha rate at location 1 and to the 112 kg N ha 1 rate at locations 2 and 3 (Table 3-6) Greater growth rates in response to N fertilizer would account for increased Ca uptake, particularly where moisture was not limiting. Magnesium increased in grain to the 168 kg N ha ^ rate at locations 1 and 2 but to the 112 kg N ha 1 rate at location 3. Iron and Mn uptake in grain were positively affected by a higher rate of N at location 1. Copper was not affected by N application. Response was identical for Cu, and Zn content was lower at location 1 than at locations 2 and 3 which responded similarly (Table 3-6) Nitrogen content of sorghum stalks was positively affected by N fertilizer at all three locations up to the 224 kg N ha ^ rate (Table 3-7). Phosphorus stalk content showed a significant increase to the 112 kg N ha ^ rate for locations 1 and 2 with no difference due to N rate at location 3. Potassium, Ca, Mg, Fe, Mn, Cu, and Zn stalk contents varied at each location and responded differently to increasing rates of N. The stalk content of each of these elements was affected by applied N (Table 3-7). Percent OM and IVOMD showed a positive response in stalks to N rate (Table 3-8). However, total OM

PAGE 94

87 Table 3-6. Response of grain nutrient content of grain sorghum to rates of anhydrous ammonia. Location N Treatment Average 12 3 kg N ha N kg ha 0 8 3 6 6 56 32 12 21 22 112 38 21 38 32 168 48 49 47 41 224 58 33 36 42 LSD 0.05 12 9 8 P kg ha" 1 0 1.3 0.9 2.0 1.4 56 4.4 2.5 6.9 4.6 112 5.4 3.9 11.7 7.0 168 8.1 4.4 14.8 9.1 224 8.1 5.0 7.6 6.9 LSD 0.05 3.1 1.6 3.5 K kg ha -1 0 2.3 1.1 2.4 1.9 56 8.4 4.3 7.9 6.9 112 9.1 6.4 13.3 9.6 168 9.8 8.3 16.0 11.3 224 10.4 7.2 7.7 8.4 LSD 0.05 3.0 2.5 4.0

PAGE 95

Table 3-6. Continued 88 Location N Treatment Average 12 3 kg N ha Ca kg ha 0 0.13 0.11 0.15 0.13 56 0.51 0.33 0.29 0.38 112 0.49 0.68 0.52 0.56 168 0.44 0.80 0.68 0.64 224 0.50 0.64 0.45 0.53 LSD 0.05 0.22 0.27 0.21 Mg kg ha 0 0.80 0.50 1.00 0.80 56 3.06 2.00 2.80 2.60 112 3.80 3.30 5.20 4.10 168 5.20 4.50 6.70 5.50 224 4.68 3.60 3.70 4.00 LSD 0.05 1.60 1.20 1.80 0 2 2 4 2 56 9 6 17 11 112 7 10 33 17 168 6 10 36 21 222 18 11 27 19 LSD 0.05 3 3 10

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89 Table 3-6. Continued Location N Treatment Average 12 3 kg N ha Mn g ha 0 1.0 0.6 1.4 1.0 56 4.0 2.3 3.4 3.0 112 3.0 3.7 5.6 3.0 168 6.0 4.5 7.3 6.0 224 5.0 5.3 4.0 5.0 LSD 0.05 1.0 1.5 2.0 Cu g ha ^ 0 0.2 0.1 0.1 0.1 56 0.7 0.4 0.5 0.5 112 0.8 0.8 0.8 0.8 168 1.1 1.0 1.0 1.0 224 1.1 0.9 0.6 0.8 LSD 0.05 0.3 0.3 0.1 Zn g kg 1 0 1.0 0.8 2.0 1.0 56 4.0 3.0 5.0 3.0 112 4.0 5.0 8.0 6.0 168 5.0 6.0 9.0 7.0 224 5.0 5.0 5.0 5.0 LSD 0.05 2.0 2.0 2.0

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90 Table 3-7. Responses of stalk nutrient content of grain sorghum to rates of anhydrous ammonia. Location N Treatment Average 12 3 kg N ha N kg ha 0 9 14 4 9 56 15 27 8 17 112 13 36. 11 26 168 33 48 17 33 224 44 64 26 45 LSD 0.05 7 12 4 „ -1 p ^ ha 0 4.0 5.0 2.0 4.0 56 6.0 7.0 3.0 6.0 112 11.0 10.0 3.0 8.0 168 8.0 11.0 3.0 8.0 224 8.0 12.0 4.0 LSD 0.05 2.0 3.0 NS* K kg ha _1 0 20 29 9 19 56 37 63 31 44 112 53 79 44 59 168 50 94 44 63 224 60 94 29 61 LSD 0.05 10 19 10

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91 Table 3-7. Continued Location N Treatment — Average 1 2 3 kg N ha Ca kg ha 0 2.0 3.0 1.0 2.0 56 5.0 8.0 5.0 6.0 112 7.0 10.0 10.0 9.0 168 8.0 10,0 11.0 10.0 224 8.0 12.0 9.0 10.0 LSD 0.05 1.0 3.0 2.0 Mg kg ha ^ 0 3.0 4.0 1.0 3.0 56 7.0 10.0 3.0 7.0 112 10.0 14.0 5.0 10.0 168 10.0 15.0 5.0 10.0 224 12.0 14.0 5.0 10.0 LSD 0.05 2.0 4.0 1.0 Fe g ha ^ 0 12 20 6 13 56 24 60 15 33 112 32 70 22 41 168 31 40 25 32 224 44 50 21 38 LSD 0.05 7 30 6

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92 Table 3-7. Continued Location N Treatment Average 12 3 kg N ha Mn g ha 0 6 8 5 6 56 12 19 16 16 112 16 23 20 20 168 19 23 22 90 224 19 25 15 20 LSD 0.05 4 8 3 Cu g ha ^ 0 0.5 0.8 0.2 0.5 56 0.9 1.7 0.5 1.0 112 1.4 3.0 0.7 1.7 168 1.2 3.0 0.8 1.7 224 1.8 3.0 0.8 1.9 LSD 0.05 0.1 0.6 0.1 "I Zn g kg 0 3 6 2 3 56 4 12 5 7 112 5 14 5 8 168 6 14 5 8 224 7 16 5 9 LSD 0.05 1 4 2 NS = Not significant at the 0.05 level of probability.

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93 Table 3-8. Response of grain sorghum grain and stalk organic matter to rates of anhydrous ammonia. Location — Average N Treatment 1 2 Stalk Grain Stalk Grain Stalk k g N ha OM dag kg 0 97.5 93.8 98.3 94.9 97.9 94.4 56 97.8 94.8 96.5 94.7 97.2 94.7 112 97.5 95.5 97.2 94.5 97.4 95 0 168 97.2 95.8 96.8 93.9 97.0 94 9 224 97.6 95.7 96.3 97.8 97.0 96.8 LSD 0.05 NS* NS NS 1.5 OM Mg ha 0 0-5 1.5 0.2 2.0 0.40 1.80 56 1-9 2.8 0.7 4.4 1.30 3.60 112 1-8 3.5 1.1 5.5 1.90 4.50 168 2 2 3.7 1.4 5.4 1.80 4.60 224 2 4 3.9 1.3 6.3 1.90 5.10 LSD 0.05 0.6 0.5 0.4 1.2 IVOMD dag kg 0 63.9 46.2 69.4 51.2 66.7 48.6 36 58.1 46.6 64.5 51.0 61.3 48.8 112 61.2 59.5 60.2 56.5 60.7 58.0 168 59.5 59.8 66.8 55.6 63.2 57.7 224 60.0 55.0 68.9 57.2 64.4 56.1 LSD 0.05 NS 5.7 7.9 4.2 DOM Mg ha 0 0.3 0.7 0.1 1.1 0.2 0.9 56 1-1 1-4 0.5 2.4 0.8 2.0 112 1-1 2 2 0.7 3.3 0.9 2.8 168 1.3 2.3 1.0 3.2 1.2 2.8 224 1-5 2.4 1.0 3.7 1.3 3.0 LSD 0.05 0.4 0.7 0.3 0.8 NS = Not significant at the 0.05 level of probability.

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94 and DOM were higher in stalks than in grain and were affected bydifferent rates of N at locations 1 and 2. Yield components increased linearly with increasing rates of N for grain yield, stalk yield, whole plant yield, and grain to stover ratio at locations 1 and 2 (Table 3-9). These yield parameters increased in a quadratic manner at location 3. Individual regression equations are shown in Table 3-9. Grain and stalk mineral concentration and content increased linearly at all locations for N and IVOMD. Only grain IVOMD concentration increased in a cubic nature at location 1 (Table 3-9). Nutrient analyses of the youngest mature leaf and whole plants at 40 days post emergence and the third leaf down the stalk from the flag leaf at bloom are shown in Tables 3-10, 3-11, and 3-12. The youngest mature leaf concentration of N, Ca, and Mg increased to the 56 kg N ha 1 rate with IVOMD increasing to the 168 kg N ha" 1 (Table 3-10). Nitrogen fertilizer rates affected the concentration of N, Ca, Mg, Mn, Cu, Zn, OM, and IVOMD when the whole plant at 40 days post emergence was analyzed (Table 3-11). Nitrogen, K, and OM increased in response to N fertilizer when the third leaf below the flag leaf was sampled at sorghum bloom (Table 3-12) Lockman (1972a, b, c) reported that Mg sufficiency values ranged from 0.20 to 0.50 dag kg for third-leaf samples of grain sorghum taken at the bloom stage. Data in Gallaher et al. (1975) indicate that grain sorghum will respond to Mg fertilization when fourth leaf tissue at the late pollination stage drops below 0.2 dag kg -1 The actual Mg sufficiency level for grain sorghum grown under similar conditions may be somewhat greater than 0.2 dag kg" 1 because both yield and Mg concentration had not leveled off at the highest rate of Mg fertilization.

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95 Table 3-9. Regression of responses of grain sorghum on rate of nitrogen applied as anhydrous ammonia. Dependent Variable Regression Equation Location 1 Grain yield kg ha Stalk yield kg ha Whole plant yield kg ha Grain/stover ^ N cone, grain dag kg N content grain kg ha N cone, stalks dag kg "'" N content stalks kg ha~l 1V0MD grain dag kg •1 -J DOM grain kg ha IVOMD stalks dag kg DOM stalks kg ha -1 -1 Y Y Y Y Y Y Y Y Y Y Y Y 526 + 426X 1369 + 633X 1895 + .38 + 1.36 + 2. -06 + .38 + 1059X 05X • 196X 11.56X 12X = -.01 + 8.7X 75.9 .57X 3 310 + 257X 44.2 + 3.08X 515 + 422X 17. 5X + 5.7X 0.60 0.75 0.74 0.20 0.70 0.78 0.71 0.82 0.16 0.61 0.37 0.80 Location 2 Grain yield kg ha Stalk yield kg ha _1 Whole plant yield kg ha Grain/ stover N cone, grain dag kg N content grain kg ha~?" N cone, stalks dag kg~ N content stalks kg ha -1 -1 -1 IVOMD grain dag kg DOM grain kg ha -*IVOMD stalks dag kg DOM stalks kg ha -1 Y = 66 + 305X Y = 2011 + 977X Y = 2097 + 1282X Y = .10 + .03X Y = 1.30 + .19X Y = -2.9 + 7.5X Y = .43 + .10X Y = 1.3 + 12. IX Y = -10.5 + 1.8X Y = 36.7 + 208X Y = 1.59 + .48X Y = 934 + 598X 0.49 0.60 0.62 0.25 0.48 0.60 0.47 0.78 0.25 0.53 0.30 0.59

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Table 3-9. Continued 9o 2 Dependent Variable Regression Equation R Location 3 Grain yield kg ha Stalk yield kg ha _^ Whole plant yield kg ha Grain/stover _^ N cone, grain dag kg N content grain kg ha -'" N cone, stalks dag kg~l N content stalks kg ha" IVOMD grain dag kg"l DOM grain kg ha -'IVOMD stalks dag kg" DOM stalks kg ha~l ,-1 Y = -2098 + 2923X 420X Y = -1570 + 2612X 367X 2 Y = -3668 + 5536X 787X 2 Y = .46 + .31X .05X 2 Y = .84 + .19X Y = 3.7 + 8.6X Y = 1:06 .59X + .1 Y = -2.6 + 5.3X ,2 0.78 0.83 0.85 0.15 0.75 0.60 0.89 0.83 *X = Coded N rate; X = 1-5; 1 = 0, 2 = 56, 3 = 112, 4 = 168, and 5 = 224 kg N ha -1

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98 S o > H o •H JJ ct) c J O c c •H 4-> CO 'J 0 N C O — I u n) u o 3 U c O Co CJ O T3 01 CS a co i rO d H c o •H 4J a u o c 01 0 z a) sh H rH I in in m m Ln cn i-i ON in O 0> ON 0> O CO' m m CO o n r-~ r~ X CO o o i — i rH co ON 0> CO Z co o i.n o un o o CM a CM Ln m rH n ai rH m c a rC c cn a •H UH •H c

PAGE 106

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102 Q S > o •H 4J n o o o -J c 00 60 00 CC o o o CM m CO — 1 CO Z r--. vC o r~ U0 m On On ON ON m o co o cn m vD cn CO cn in m m m on On ON ON 3 T3 a ID e . in CM CD cn cn cn CO cn CO CO m O o r- r~CM o m i— 1 a CD -* r i H i — 1 H m o in Ln CO o r~ CM vO m cO cO o m cO in o o CM uO CO
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103 Nitrogen, P, and K concentration ranged from 1.95 to 3.12 dag kg 0.23 to 0.24 dag kg -1 and 1.75 to 2.09 dag kg" 1 respectively, when the youngest mature leaf at 40 days post emergence was used as the diagnostic sample (Table 3-10). Potassium actually decreased as rate of N fertilizer increased. Nitrogen, P, and K concentration ranged from 1.72 to 2.93 dag kg" 1 0.28 to 0.32 dag kg" 1 1.60 to 1.73 dag kg" 1 respectively, when the whole plant at 40 days was used as the diagnostic sample (Table 3-11). As with the leaf sample, K concentration decreased with increasing N fertilizer. Nitrogen, P, and K concentration ranged from 1.67 to 1.77 dag kg \ 0.22 to 0.30 dag kg and 2.74 to 3.00 dag kg" 1 respectively, when the third leaf below the flag at bloom was used as the diagnostic sample (Table 3-12) Both P and K concentration decreased with increasing N fertilization. Critical nutrient levels (CNL) for grain sorghum are not well established, but Lockman (1972a, b, c) stated that leaf N in grain sorghum at several vegetative stages was highly correlated with final grain yields. He further suggested that deficiency levels for the third leaf below the flag at bloom stage were in the order of 2.5 to 3.2 dag kg" 1 N. Sorghum grain yields decreased as leaf N at full bloom dropped below 2 dag kg Leaf N at this stage accounted for about 63% of the variation in grain yields. Eylands (1984) found that applied N increased nutrient concentrations of P, Ca, Mg, Fe, Zn, Mn, and Cu, and decreased K in the diagnostic leaf of grain sorghum when following either crimson clover (Trifluim incarnatum L.) or lupine ( Lupinus angustif olius L.). Grain N and whole plant N content of grain sorghum also increased with applied N, as did grain nutrient levels exceeding 100 kg ha correlating to

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104 diagnostic leaf N levels of 3.35 dag kg ^ or higher. Approximately 2.9 dag kg ^ N was needed in the diagnostic leaf of grain sorghum for maximum grain yields. Correlation coefficients were utilized to compare these three sampling techniques for predicting grain, stalk, and whole plant DM yields. The correlation coefficients for locations 1 and 2 are given in Table 3-13. Correlation coefficients for yield with nutrients determined at final harvest are found in Appendix Tables B-2 through B-19. Correlation coefficients for predicting grain yield showed that N concentration was positively correlated to final grain yield by all three sampling techniques with a tendency for the whole plant at 40 days post emergence to give the highest correlations (Table 3-13) When the youngest mature leaf at 40 days was sampled N, Ca, Zn, DM, and IVOMD were positively correlated to grain yield (Table 3-13). Only N and IVOMD were positively correlated to stalk or whole plant DM yields with this sampling technique. When the whole plant was sampled at 40 days N, Ca, Mg, Fe, Mn, Cu, and IVOMD were all positively correlated to final grain yield and N, Ca, Mg, Mn, Zn, and IVOMD were positively correlated to stalk and whole plant DM yields. Potassium was negatively correlated with grain yield while plant DM concentration was negatively correlated with grain, stalk, and whole plant DM yield. When the third leaf below the flag leaf at bloom was sampled, N was the only nutrient positively correlated with grain yield at both locations (Table 3-13) Nitrogen and OM were positively correlated with stalk yield with P negatively correlated. Nitrogen, Ca, Mg, and OM were positively correlated with whole plant DM yield while P was negatively correlated. The lack of P being correlated to grain yield

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105 Table 3-13. Correlation coefficients to p redict grain stalk, and whole plant dry matter yield for grain so rghum at two locations Youngest mature Whole plant Third leaf flag leaf at 40 days at 40 days at bloom Location Location Location 1 2 1 2 1 2 _i Han Wo ud 6 ^6 gra'in <.g ha N U 0^4 u / O A 71 U ol A / O 0 43 p No' 5 N o A /. 1 XT r* NS -0. /I NS V IX INb a c; i -U Jl -U Jo A -0 63 NS A Aft U Ho a iq u jy A 7") A 1 O NS 0. 40 Mo U JO NS A 7 T n to U 11 NS 0 43 MC o. /y 0. 55 NS NS IN b A /.A A C c U 55 A / / U 44 NS NS Cu M C No No A C A 0 50 0 37 -0.46 NS Zn a -0 41 A / O 0 48 NS -0.41 NS DM a / r A c; / -0.54 A / £ -0 46 -0 40 NS NS AM Url A C "7 0.5/ NS NS NS 0.64 NS T VAMT) 0.65 0.52 0.39 0.72 NS NS stalks kg ha ^ M IN 0.49 0.80 0.89 0.74 0.67 0.59 p NS NS 0.54 NS -0.58 -0.49 K NS -0.62 -0.71 NS NS NS La 0.48 NS 0.84 0.70 NS NS 0.46 NS 0.87 0.59 0.42 NS r e -0.37 0.43 0.58 NS NS NS Mn NS NS 0.64 0.38 0.42 NS Cu NS NS 0.58 NS -0.44 NS Zn -0.42 NS 0.58 0.47 -0.49 NS DM -0.48 0.41 -0.50 -0.62 NS NS OM 0.61 NS NS NS 0.64 0.55 IVOMD 0.74 0.40 0.66 0.73 NS NS

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106 Table 3-13. Continued Youngest mature Whole plant Third leaf flag leaf at 40 days at 40 days at bloom Location Location Location 12 12 12 dag kg whole plant kg ha N 0.52 0.81 0.89 0.78 0.68 0.58 P NS NS 0.51 NS -0.66 -0.47 K NS -0.56 -0.68 NS -0.49 NS Ca 0.50 NS 0.83 0.75 0.38 0.38 Mg 0.53 NS 0.87 0.63 0.41 0.37 Fe -0.46 0.45 0.52 NS NS NS Mn NS NS 0.63 0.42 0.40 NS Cu NS NS 0.58 NS -0.47 NS Zn -0.52 NS 0.56 0.42 -0.48 NS DM -0.48 0.47 -0.51 -0.61 NS NS OM 0.62 NS NS NS 0.68 0.53 IVOMD 0.74 0.45 0.57 0.76 NS NS *NS = Not significant at the 0.05 level of probability.

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107 in this study is in contrast to the findings of Lockman (1972b). The variability of K, Zn, and Cu may be explained by the fact that nutrient uptake generally increases with yield but total nutrient contents vary widely due to location, soil types, and hybrids (Fribourg et al., 1976), Lockman (1972b) found that Cu levels were not well correlated with yields. Higher Cu levels were noted with later samples in a dry year. Iron levels in grain sorghum generally were not well correlated with yield (Lockman, 1972b). However, in the current study Fe concentrations in all three sampling techniques were moderately to highly correlated with grain, stalk, and whole plant DM yields. Conclusions Grain sorghum DM yield for grain and whole plant increased at the 56 kg N ha ^ rate at two locations and to the 112 kg N ha rate for the third location. Residue DM yield increased to the 112 kg N ha~^~ rate at all locations. Sorghum webworm at location 2 and moisture deficits at location 1 had a greater effect on grain yields than residue yields. As with corn, the 224 kg N ha ^ fertilizer rate reduced yields where moisture was deficient. Grain yield and whole plant yield averaged over the three locations were 560 and 342% higher than the control at the 168 kg N ha ^ rate, respectively. Grain N concentration increased to the 112 kg N ha 1 rate at location 1 and to the 224 kg N ha 1 rate at locations 2 and 3. The grain concentration of P, K, Ca, Mg, Fe, Mn, Cu, and Zn were not affected by N fertilizer at any location. Iron concentration did show increases to 168 kg N ha rate only at location 1. The concentration of nutrients in sorghum stalks increased with increasing rates of N fertilizer.

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108 Whole plant N content was 39, 58, 74, and 87 kg ha for application of 56, 112, 168, and 224 kg N ha respectively. Efficiencies of N uptake were 43, 38, 35, and 32% for 56, 112, 168, and 224 kg N ha" 1 respectively It appears that concentration of certain nutrients, particularly N, in the youngest mature leaf at 40 days post emergence, whole plant at 40 days, and third leaf below the flag leaf at bloom can all be used as good predictors of grain yield and whole plant DM. Sampling of whole plants at 40 days gave higher correlations for N and Ca as predictors than did the leaf analyses to predict final yield of grain, residue, and whole plant DM yields.

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CHAPTER 4 YIELD AND CHEMICAL COMPOSITION OF BAHIAGRASS AS INFLUENCED BY NITROGEN RATE, SOURCE, AND APPLICATION METHOD Introduction There are millions of acres of improved bahiagrass ( Paspalum notatum L. Flugge) pasture in the southeastern United States This pasture grass is easily maintained and provides beef cattle producers with an acceptable forage to let cattle graze during late spring, summer, and early fall. The productivity and quality of bahiagrass can be improved by proper application of N fertilizer which has been studied by many researchers (Beaty et al., 1960, 1977; Blue, 1966, 1972, 1974; Stanley et al., 1977). However, with low beef prices and increased cost for N fertilizer much of this pasture is never fertilized adequately for good forage quality and productivity. Nitrogen is the largest and most expensive component of bahiagrass fertilization. While anhydrous ammonia (NH^) is one of the least expensive sources of available N, research in the 1950s conducted by Blue and Eno (1954) and later (Blue, 1984) indicated that up to 40% of the applied N could be lost due to volatilization of ammonia. This loss was dependent upon the cation exchange capacity (CEC) of the soil, soil temperature, moisture, pH of the soil, and spacing of injectors. Since the 1950s new and improved application equipment is in use that may make the utilization of anhydrous ammonia more 109

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110 economical than other sources of N. The cost of N from ammonium nitrate (34% N) is 2.4 times that of anhydrous ammonia (82% N) Many studies have been conducted concerning the use of various N rates and sources for fertilization of bahiagrass. These studies all showed significant responses to increasing N rates as well as increased N content of forage (Beaty et al., 1960, 1963, 1977, 1980; Blue, 1966, 1972, 1974). However, very limited information is available on the response of bahiagrass to anhydrous ammonia as a fertilizer source of N. The efficiency of using anhydrous ammonia in comparison to other sources of N on crops has been studied by many investigators. Tucker and Crowe (1966) summarized the results of many investigations testing the effectiveness of various sources of N on several crops in comparison to anhydrous ammonia. They concluded that anhydrous ammonia was equal to most other N sources. The results of most experiments on forage indicate that, during the year of application, yields are somewhat greater from grasses fertilized with ammonium nitrate (NH^N0 3 ) in split applications than with anhydrous ammonia applied in one application at rates of 112 to 324 kg N ha -1 (Tesar, 1974). Burton and Jackson (1962) conducted trials on 'Coastal' bermudagrass ( Cynodon dactylon L.) for 5 years utilizing anhydrous ammonia as one source of N. The anhydrous ammonia was applied in 40 cm rows with a chisel-type knife. Total yields were greater for ammonium nitrate fertilized grass at the 112 and 224 kg ha""*" rates of N if fertilizer was applied in split applications. When the fertilizer was applied in one application in mid-March, anhydrous ammonia was equal to ammonium nitrate in effectiveness. Hill and Tucker (1968) found yields equal for all sources and all clippings

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Ill at lower rates of N application. At higher rates of N application, anhydrous ammonia produced lower yields in the first clipping and higher yields in succeeding clippings. The lag in response was attributed to sod burn from escaping ammonia. Reducing the applicator knife spacing tended to increase N1U retention, decreased sod burn, and increased the NH^ efficiency at the high rates of N application. Lechtenberg et al. (1974) using anhydrous ammonia to fertilize smooth bromegrass ( Bromus inermis Leyss.), found that it was as effective in increasing animal production per hectare as was ammonium nitrate at the same application rate. The objective of this study was to determine the effect of anhydrous ammonia versus ammonium nitrate as sources of N on the yield and chemical composition of bahiagrass forage. Materials and Methods Experiments were conducted at two locations during 1983 and one location during 1984. All locations were in Levy County, Florida, latitude 2930' North, longitude 8230' West. Five rates of N (0, 56, 112, 168, and 224 kg N ha" 1 ) were whole plot treatments within which each of the split plot sources of N (ammonium nitrate and anhydrous ammonia) and were randomized and replicated four times (Table 4-1). Treatments were applied during 1983 on June 8 at location 1 and on June 11 at location 2. Location 3 received all treatments on May 29, 1984. All locations had been in bahiagrass sod for 15 years. Location 1 was a Kershaw fine sand (thermic, uncoated, typic Quartzipsamment) an excessively drained soil. Locations 2 and 3 were on a Candler series

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112 Table 4—1. Statistical analysis model used for bahiagrass data. Split-plot design. Source df TOTAL 39 (rTS-1) Total whole plots 19 (rT-1) Replications (r) 3 (r-1) Whole plot (T) 4 (T-l) ERROR A 12 (r-l)(T1) TOTAL split plot 20 (rTS-1) (rT-1) Split Source (S) 1 (S-l) Whole plot x split source 4 (T-1)(S1) ERROR B 15

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113 (hyperthermic, uncoated, typic Quartzipsamment) also an excessively drained, rapidly permeable soil. Split plots were 3 x 10 m. Anhydrous ammonia was injected 15 cm into the bahiagrass sod utilizing a DMI "Sod Booster" applicator developed by DMI Inc., Goodfield, Illinois. The applicator is a pull type unit with nine spring-loaded shanks on 35.5 cm spacings with adjustable knives and a packer wheel behind each knife. A continental A-6503 regulator was utilized to regulate the anhydrous flow. Ammonium nitrate was broadcast by hand to all plots receiving this treatment. All plots at all locations were fertilized with a broadcast application of 80 kg K ha" 1 25 kg S ha" 1 and 12 kg Mg ha 1 prior to applying N treatments. Sources of K, S, and Mg were K^SO^rMgSO^ (K-Mag) and KC1. All plots were harvested with a rotary type mower with a grass catching attachment. Clipping height was 2.5 cm. Harvest size was 1 x 7 m with all plots being harvested at 13-week intervals until October of each year when cool temperatures and dry weather severely limited growth. Stolon root samples were obtained by taking three 12.5 cm diameter cores to a depth of 15 cm from each split plot both prior to and following final harvest. Treatment and harvest dates are shown in Table 4-2. These samples were washed thoroughly to remove soil. Both forage and stolon root samples were dried in a forced air oven at 70 C, then ground in a Wiley mill through a 1 mm stainless steel screen. Soil samples were taken following final harvest at depths of 0-20 and 20-40 cm. Soil sample results are shown in Appendix Table C-l. Chemical analyses of soil and plant tissue was

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114 CC CT C o eg a z n cc CXi c fO CJ 0 -J o — to -J (J cO C G E o i — i H CM CXI rH in vD co CM 00 co CJ H c-j r1 o o CO 0> 1 — 1 m CM co i — I CO co ON C7% CM O c J c I — I CO CO CM on o o o3 CO 4-1 rH C p. cu Cl, E CO CO 4J 4J 4J 4-1 4J CO 4-1 cu co co 10 CO co CJ rd rH w 0) 0) OJ CJ CJ rH CJ a. 4_> > > > > CX 0) u e c c M u u S r^ H a CO CJ c3 CO CO Clj cd a, o CO B rC JC co a H 4-J a C! CC CU CJ CJ CJ CJ c CO CM to O CJ 00 00 CO CD cr o 1 u rH in CO n cO C3 rH rH -i u o •H Cu 4-1 o o o 0 c 4-J O a) o C/J P* Pn c^ CirK CO CO rH CM CO m

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115 determined as described in the Materials and Methods section of Chapter 2. A split-plot statistical analysis was performed according to Cochran and Cox (1957). Statistical analysis was performed according to the description given in Chapter 2. Average yields were determined for each location and used to determine the cost Mg 1 of forage produced at each rate of N, cost Mg of forage produced by each 56 kg increment of N, and forage production efficiency of applied N (kg of DM produced kg 1 N applied). Recovery of applied N was calculated by the following equation: N uptake (treatment) N uptake (control) x 100 1i ; — ^ — -. r — = Percent N recovery annual N application (treatment) The cost of anhydrous ammonia was calculated at $16.00 ha 1 for application plus $.26 kg 1 material (82% N) applied which computes to a cost of $.32 kg" 1 of applied N plus $16.00 ha" 1 at each rate of N. The cost of ammonium nitrate was calculated at $.215 kg 1 of material (34% N) or $.63 kg" 1 of N. Results and Discussion No differences in total seasonal dry matter (DM) yield were found between sources of N except at location 1 at the 112 kg N ha 1 rate in favor of anhydrous ammonia, and at the 168 and 224 kg N ha 1 rates for ammonium nitrate (Table 4-3) There were also differences between sources at individual harvest dates (Table 4-4) with the last harvest at location 1 and the first harvest at location 3, where yield was 21% greater for anhydrous ammonia.

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116 Table 4-3. Influence of N source and rate on forage yield and nutrient concentration of bahiagrass. Location 1 Location 2 Location 3 N Rate — — — — Average NH„ NH,NCL NH„ NH.N0 o NH„ NH.NOkg ha DM kg ha 0 2350 2600 2500 2340 2340 1830 2320 56 5540 5840 4830 4800 3650 3120 4630 112 6980 6170 5230. 5560 3240 3750 5155 168 6690 7250 6280 6200 4550 3880 5805 224 6850 7350 7110 6660 5330 5170 6410 LSD .05 Rate 700 750 1000 LSD .05 Source 470 NS* NS N dag kg ^ 0 1.46 1.27 1.03 1.16 1.40 1.40 1.29 56 1.43 1.45 1.13 1.35 1.39 1.59 1.39 112 1.67 1.54 1.35 1.44 1.52 1.72 1.54 168 1.78 1.70 1.51 1.46 1.72 1.82 1.66 224 1.81 1.93 1.51 1.35 1.82 1.89 1.76 LSD .05 Rate .16 .15 .13 LSD .05 Source NS .06 .05 IVOMD dag kg" 1 0 35 38 27 30 — — 32 56 38 41 28 32 — — 35 112 37 41 33 33 — -36 168 38 42 31 33 — — 36 224 39 46 34 38 — — 39 LSD .05 Rate 2 2 LSD .05 Source 2 2

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117 Table 4-3. Continued Location 1 Location 2 Location 3 N Rate — — Average NH 3 NH 4 N0 3 NH 3 NH 4 NC> 3 NH 3 NH 4 N0 3 kg ha Fe mg kg 0 583 671 804 753 994 858 777 56 723 638 706 550 760 533 652 112 664 573 551 483 579 556 568 168 629 602 532 483 575 377 533 224 673 581 537 446 533 430 533 LSD .05 Rate NS 105 135 LSD .05 Source NS 42 55 Mn rag kg ^ 0 84 84 92 90 109 102 94 56 85 80 81 83 97 93 87 112 85 86 77 80 96 91 86 168 85 83 76 75 92 91 84 224 84 92 81 79 97 100 87 LSD .05 Rate NS NS NS LSD .05 Source NS NS NS Cu mg kg 1 0 6555555 56 5555555 112 6 6 6 6 5 6 6 168 6 6 6 5 6 6 6 224 6 6 6 6 6 6 6 LSD .05 Rate .3 -5 .40 LSD .05 Source NS NS NS

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118 Table 4-3. Continued Location 1 Location 2 Location 3 N Rate — — — — — Average NH„ NH, N0„ NKL NH,N0„ NH„ NH,NO„ kg ha Zn mg kg 0 29 27 57 58 50 50 45 56 23 24 67 39 39 36 38 112 22 25 63 43 34 36 37 168 23 28 42 45 36 37 35 224 27 26 63 65 37 38 38 LSD .05 Rate NS 11 9 LSD .05 Source NS NS NS -1 p d a g ha 0 0.18 0.18 0.13 0.13 0.17 0.17 0.16 56 0.17 0.22 0.12 0.14 0.16 0.17 0.17 112 0.18 0.19 0.14 0.16 0.18 0.19 0.18 168 0.17 0.19 0.15 0.17 0.18 0.20 0.18 224 0.19 0.22 0.16 0.16 0.19 0.20 0.19 LSD .05 Rate NS .01 .01 LSD .05 Source .01 .01 .01 P kg ha" 1 0 453343 4 56 10 4 6 7 6 6 8 112 10 13 8 9 6 7 9 168 12 14 9 11 9 8 10 224 13 16 11 10 10 11 12 LSD .05 Rate 2.2 1.4 2.0 LSD .05 Source 1.5 NS NS

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119 Table 4-3. Continued Location 1 Location 2 Location 3 N Rate Average NH„ NH,N0 o NH„ NH,NO_ NH NH.NOkg ha : Ca dag kg 0 0.53 0.48 0.41 0.40 0.46 0.43 0.45 56 0.40 0.43 0.38 0.40 0.40 0.42 0.41 112 0.44 0.47 0.37 0.39 0.40 0.41 0.42 168 0.41 0.41 0.34 0.37 0.39 0.41 0.39 224 0.44 0.43 0.35 0.41 0.39 0.39 0.40 LSD .05 Rate NS .03 .03 LSD .05 Source NS NS NS Ca kg ha 0 13 12 10 9 10 8 10 56 22 24 18 19 15 13 18 112 29 28 24 23 13 15 22 168 27 28 18 20 17 16 21 224 30 30 24 26 20 20 25 LSD .05 Rate 2.0 3.0 3.4 LSD .05 Source NS NS NS NS = Not significant at the 0.05 level of probability.

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120 c c H 4J cO o O (U u M 3 O oo c CJ to 0 M -J H Z C 0 H AJ 33 H 0) OO CO co CO z z Z z o o o o I -T c oo cjx j CN r^ c i 1 — 1 H CN > AJ •H rH H o o o o I CTi CO o CN C3 AJ H rH rH JD rH — I rH CN C rH M H ft CD to iah Xl 4-) 0 o to n a> i — 1 > a) > <-H CO a) 0 J* rH •JC r^ to CO CO oo a m Z Z Z z CO ai o > cu a) o O O o o o rH cn CN o 4-) co rH 00 CO a) CJ in rH CN o AJ to O AJ CO cd a -a J3 AJ AJ rH o O O o o CM AJ CI o CXI in oo u ct) rH CXI — 1 30 CI II •H rH H CN cm AJ M H C cu c w oC a E •H •H 3 w cm Z H AJ C u c M to Z H co > ii ii cd CO rH CN r-i u-i z CO

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121 At location 3 there was limited rainfall between N application and first harvest, thus giving the anhydrous ammonia an advantage for plant uptake. The higher DM yield at location 1 is in agreement with Burton and Jackson (1962) who found a greater carryover effect in the year after application favoring anhydrous ammonia over ammonium nitrate when used for bermudagrass fertilization. Hill and Tucker (1968) had similar results at higher rates of N ha and attributed low yields at the first harvest to sod burn and escaping ammonia. Likewise, Tesar (1969), and Tesar et al. (1972) measured the residual effects of anhydrous ammonia in the year following fertilization and found greater yields from grass fertilized with anhydrous ammonia than with ammonium nitrate. Schoer and Tesar (1977) noted greater carryover of N after a dry year at rates of 45 and 90 kg N ha ^ from ammonium nitrate. In most studies on tropical forages, anhydrous ammonia consistently gave the lowest yields in the first cutting and higher yields in subsequent cuttings Dry matter yield responded to the 112, 224, and 168 kg N ha 1 rate for anhydrous ammonia and to the 168, 112, and 224 kg N ha rate for ammonium nitrate at locations 1, 2, and 3, respectively. The overall mean DM yields over all sources and rates ranged from 2320 kg ha 1 for 0 N ha _1 to 6410 kg ha" 1 at 224 kg N ha" 1 (Table 4-3). There were interactions between location and rate when data were combined. The range in yields at 2.5 cm clipping height is consistent with that found by Blue (1966, 1977, 1980, 1983) and Beaty et al. (1976, 1977). Nitrogen concentration varied due to source at locations 2 and 3 with a greater concentration due to ammonium nitrate. In general, N concentration increased with increasing rate of N for both anhydrous ammonia

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122 Or ammonium nitrate (Table 4-3) The concentration of mineral elements in forage is dependent on the interaction of a number of factors, including soil characteristics, plant species, stage of maturity, yield, pasture management, and climate (McDowell et al., 1983). Nitrogen concentrations were slightly higher than those found by Blue (1972) over 6 years of N fertilization at similar rates utilizing different sources of N. The IVOMD responded to increasing rates of N and was higher with ammonium nitrate at most rates (Table 4-3). The IVOMD concentrations ranged from 32 to 39 dag kg -1 when averaged over sources, locations, and N rates. These values are lower than those found by other researchers (Moore et al., 1970; Prates et al., 1974; Ruelke and Prine, 1971). Some researchers have reported increases in digestibility of N fertilized forage while others have reported no difference due to the application of N fertilizers (Ford and Williams, 1973). Waite (1970) noted an increase in the IVOMD of orchardgrass ( Dactylis glomerata L.) and ryegrass ( Lolium multiflorum Lam.) with N fertilization. Fribourg et al. (1971) noted an increase in IVOMD of bermudagrass from 37 to 46% as N applied increased from 0 to 800 kg ha Others have shown no difference due to N rate (Ruelke and Prine, 1971; Webster, 1965). Nitrogen fertilizer stimulates rapid growth which possibly causes lower levels of soluble and structural carbohydrates and a higher digestibility (Waite, 1970). Stanley et al. (1977) found that when bahiagrass was fertilized with 0 to 336 kg N ha 1 and clipped to height from 0-12.5 cm above the stolons that cell wall constituents of the forage ranged from 70-72% and were not influenced by N fertilization

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123 or clipping height. Wilson (1973) using Panicum maximum var. triaho glume found that increasing N from low to moderate levels increased digestibility by 3-5% and had a small positive effect on the percentage of total soluble carbohydrates. Lechtenberg et al. (1974) utilizing smooth biromegrass ( Bromus inermis Leyss.) fertilized with anhydrous ammonia at rates ranging from 0 to 448 kg N ha found that anhydrous ammonia was as effective as ammonium nitrate in increasing animal production per hectare. Also, the level of N fertilization had no effect on percent IVOMD. During 1983 and 1984 the ambient temperatures were higher than normal and less rainfall than average occurred during the harvesting period June through October. Henderson and Robinson (1982b) studied environmental influences on yield and in vitro true digestibility (IVTD) of warm season perennial grasses. They found that DM yield increased with increasing photon flux density and temperature. In all grasses studied including 'Pensacola' bahiagrass IVOMD consistently decreased as temperature increased. Henderson and Robinson (1982a) found negative correlations between IVOMD and concentrations of acid detergent fiber (ADF) cellulose, permanganate lignin (Lig) and silica. In a review of the literature, Cooper and Tainton (1968) stated that growth rates of most tropical grasses increased with temperature from 30 to 35 C and light intensity to 60,000 lux or higher. Conditions favoring maximum growth rates have frequently resulted in lower forage quality. High temperatures during rapid growth periods have been related to increased proportions of stems, increased fiber concentrations, decreased water soluble carbohydrate concentration, and reduced herbage digestibility of tropical

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124 grasses (Henderson and Robinson, 1982b; Wilson and Ford, 1973; Wilson et al., 1976; Wilson and Minson, 1980). Wilkinson and Langdale (1974) stated that adequate N concentration in 'Pensacola* bahiagrass appears to be in the range of 1.8-2.2 dag kg These levels were reached at only the highest N rates of 168 and 224 kg N ha 1 in the current study (Table 4-3). Brown and Ashley (1974) reviewed the literature pertaining to N metabolism and carbohydrate reserves in plants and found that N fertilization, particularly of grasses, increases N content which is associated with growth resulting from high N rates and they concluded that carbohydrate reserves would be limited under such conditions. Gallaher and Brown (1977) found evidence to indicate that the photosynthate is not utilized for new growth or metabolism when N is deficient but accumulates in bundle sheath cells in the form of starch. More starch in the leaves of N deficient leaves of bahiagrass is in agreement that N stimulates the translocation of assimilates from leaves and their utilization with a corresponding reduction in carbohydrate accumulation in the leaves. It has been shown that age of the forage has a direct effect upon digestibility (Moore et al., 1970; Prates et al., 1974). A possibility for the greater digestibility from ammonium nitrate could be due to destruction of bahiagrass stolons during the injection process of NH^ where more soluble carbohydrates would be utilized to rebuild cells and structural carbohydrates in the stolonif erous root systems (Sampaio and Beaty, 1976). Insufficient rainfall and increased temperatures apparently influenced all parameters measured overa all locations and harvest dates (Table 4-5) This effect has been reported in other N rate studies as noted previously

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125 Table 4-5. Rainfall data for bahiagrass experiments conducted during 1983-84 at three locations. 1983 1984 Date Location 1 Location 2 Location 3 mm 5/15 • 5/20 5/25 58 5/30 91 6/5 6/10 102 6/15 15 6/20 6 58 15 6/25 23 23 6/30 101 74 7/5 25 114 38 7/10 13 6 7/15 7/20 7/25 20 38 114 7/30 19 46 6 8/5 33 79 8/10 8/15 15 8/20 76 101 63 8/25 6 8/30 9/5 9/10 9/15 13 13

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126 Phosphorus concentration also was higher at most rates of ammonium nitrate over anhydrous ammonia (Table 4-5) The concentration of P was found to be deficient in studies by Rojas (1985) He found that most bahiagrass hays were likely to be deficient in P, Na, Cu, Co, Fe, and Zn at all stages of maturity. Mean concentrations of all elements except K at 0 N rate, or P and Cu at all rates of N in forage DM would meet the National Research Council (NRC) requirements of a 450 kg body weight beef cow of average milking ability (Table 4-6) Total kg P ha ^ responded due to source only at location 1 at the 56, 168, and 224 kg N ha ^ rates. Phosphorus increased with rate and responded to the 56 to 224 kg ha ^ rates depending on location and N sources. Reid and Jung (1965) found that P fertilized tall fescue had a higher content of soluble carbohydrate and a higher IVOMD. Iron concentration also varied due to source and rate with concentrations being higher in the anhydrous ammonia treated forage at the 56 and 0 kg N ha ^ rates at locations 2 and 3, respectively (Table 4-3). This could possibly be due to contamination of samples with soil as the Fe concentration was highest at the 0 rate and decreased through 168 kg N ha ^ when locations were averaged. Calcium, Mn, Cu, and Zn concentrations were changed from N application but not by source of N (Table 4-3). No differences due to sources of N were found for OM, N, K, or Mg contents or K or Mg concentrations in forage (Table 4-7) The N content increased with the 168 kg N ha ^ rate at location 1 and to the 224 kg N ha ^ rate at locations 2 and 3. The bahiagrass stolonif erous root system and its response to N rates and sources have been studied by several researchers (Beaty

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127 Table 4-6. Mineral concentration means of bahiagrass at all locations as related to critical levels in beef cattle nutrition. N Rate kg ha Mineral SVR 56 112 168 224 ** dag kg 1 Phosphorus 0.23 0.16 0.17 0.18 0.18 0.19 Potassium 0.65 0.62 0.73 0.81 0.86 0.88 Calcium 0.28 0.45 0.41 0.40 0.40 0.40 Magnesium 0.10 0.23 0.22 0.25 0.25 0.22 mg kg 1 Iron 50 777 652 568 533 533 Manganese 40 94 8 7 8 b 84 87 Copper 8 5 5 5 6 6 Zinc 30 45 3S 34 38 38 Suggested value of requirement (NRC, 1984) ** Suggested weight of value 450 kg for beef cows (NRC, 1984). with average milking ability and body

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128 Table 4-7. Influence of N rates on nutrient content of bahiagrass. Location N Rate Average 12 3 kg N ha : OM kg ha 0 1990 1790 1600 1790 56 4290 3790 2630 3570 112 5080 4270 2850 4067 168 5360 525.0 3580 4730 224 5240 5750 4450 5150 LSD .05 350 600 700 N kg ha ^ 0 30 30 30 30 56 80 60 50 60 112 100 80 60 80 168 120 80 80 90 224 120 100 100 110 LSD .05 10 10 20 K dag ha 0 0.70 0.60 0.55 0.62 56 0.79 0.82 0.57 0.73 112 0.86 0.91 0.69 0.81 168 0.95 0.95 0.69 0.86 224 0.94 0.96 0.75 0.88 LSD .05 .08 .08 .08

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129 Table 4-7. Continued Location N Rate Average 12 3 kg N ha : K kg ha 0 20 20 10 15 56 50 40 20 40 112 60 50 20 43 168 70 6Q 30 53 224 70 70 40 60 LSD .05 7 8 8 M g dag kg 1 0 0.28 0.20 0.21 0.23 56 0.27 0.20 0.20 0.22 112 0.30 0.22 0.22 0.25 168 0.30 0.22 0.24 0.25 224 0.33 0.24 0.24 0.22 LSD .05 0.03 0.02 0.01 0 7 5 4 5 56 16 10 7 11 112 21 12 8 14 168 22 14 10 15 224 23 17 13 18 LSD .05 2 2 2 Total of all cuttings at each location.

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130 et al., 1980; Blue, 1972, 1977; Blue et al., 1979; Blue and Graetz, 1977; Impithuksa and Blue, 1978; Rodriquez et al., 1973). Rodriquez et al. (1973) stated that 'Pensacola' bahiagrass produces massive stolon-root systems with relatively high crude protein concentrations. Some IVOMD studies indicated 59% digestibility of this material. Blue (1972) and Blue and Graetz (1977) found that the stolonif erous root system stores N and that N concentration ranged from 0.36 to 1.02 dag kg with 0 to 224 kg N ha ^ applications, respectively, and varied with the number of N applications and sources. In the current study, there were no differences due to N sources for any of the nutrients measured except for P. Phosphorus increased more to ammonium nitrate than to anhydrous ammonia at locations 1 and 3 (Table 4-8). Yield and concentration of DM, OM, IVOMD, N, K, Ca, Mg, Fe, Mn, Cu, and Zn are found in Tables 4-9 through 4-11. There was no difference due to rate of N for DM yields, IVOMD, and OM ha The nutrient content of N increased to the 112 kg N ha ^ rate only at location 1. The content of K, Ca, and Mg in forage varied due to N rate only at location 3 (Table 4-10). The concentration of nutrients varied among locations with the following results: N concentration responded to 224 kg N ha ^ at location 1 and to 56 kg N ha at location 2 (Table 4-9). Potassium and Ca responded to N rate with K responding to 112 kg N ha ^ at location 1. Calcium concentration decreased with increased rate of N at location 1 and showed no response at the other locations. Iron, Mn, Cu, and Zn concentrations in forage were not different at any location (Table 4-9) Recovery of applied N is shown in Table 4-12. Recovery tended to follow the same trends as those identified by Beaty et al. (1964) and

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131 CO o z en z C U-l O O •H 4-1 0) cfl u CJ M O 3 rJ o co m EC T3 z C cfl 0) •u cfl u >. XI n TD O CD CJ 4-1 3 -H z c CO d a) O 4-1 rH Cfl O 4-1 CO 2 o o m o rH rH rH CN rH
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132 Table 4-9. Nutrient concentration of bahiagrass stolons as influenced by rate of nitrogen at three locations. Stolon N Rate N P K Ca Mg kg ha ^ dag kg Location 1 0 .15 .08 .22 .35 .16 56 .16 .07 .21 .32 .15 112 .27 .07 .24 .29 .14 168 .26 .06 .23 .30 .15 224 .35 .06 .20 .28 .14 LSD .05 .07 .01 .03 .03 NS* Location 2 0 .10 .05 .16 .20 .19 56 .19 .07 .20 .21 .09 112 .15 .09 .20 .19 .10 168 .17 .08 .21 .20 .09 224 .19 .06 .19 .19 .11 LSD .05 .06 NS NS NS NS Location 3 0 .45 .10 .31 .34 .15 56 .47 .09 .28 .33 .13 112 .44 .08 .23 .32 .13 168 .45 .08 .24 .26 .12 224 .56 .09 .28 .31 .20 LSD .05 NS NS NS NS NS

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133 Table 4-9. Extended Stolon N Rate Fe Mn Cu Zn kg ha 1 rag kg 1 Location 1 0 1046 77 4 22 56 1030 77 4 21 112 1126 72 3 19 168 1068 .83 4 19 224 1070 78 7 27 LSD .05 NS NS NS NS Location 2 0 56 112 168 224 1045 991 1074 1017 935
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134 Table 4-10. Nutrient content in bahiagrass stolons as influenced by rate of nitrogen at three locations. Stolons N Rate K Ca Mg kg ha ^ kg ha Location 1 0 8 13 20 9 56 9 13 19 9 112 15 13 16 8 168 15 13 17 8 224 17 10 14 7 LSD .05 5 NS* NS NS Location 2 0 4 7 8 8 56 7 8 8 4 112 6 7 7 4 168 7 8 8 4 224 7 7 7 4 LSD .05 NS NS NS NS Location 3 0 5 3.2 3.5 1.6 56 7 4.0 4.6 1.8 112 8 4.1 5.8 2.3 168 9 4.8 5.1 2.4 224 9 4.6 5.3 3.3 LSD .05 NS 0.8 1.2 0.9 NS = Not significant at the 0.05 level of probability.

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135 Table 4-11. Yield and digestibility of bahiagrass stolons as influenced by nitrogen rate at three locations. Stolons N Rate DM DM OM IVOMD kg ha Location 1 0 56 112 168 224 LSD .05 -1 kg ha 5,700 6,080 5,490 5,600 4,610 NS* dag kg 34.8 40.6 45. .4 37.4 38.2 2.2 kg ha 1,970 2,490 2,490 2,080 1,870 NS dag kg 25.2 25.2 26.7 31.5 27.0 NS -1 Location 2 0 56 112 168 224 LSD .05 3,850 3,880 3,630 4,080 3,600 28.8 33.5 40.6 35.3 36.0 5.5 1,070 1,250 1,510 1,430 1,280 NS 37. 31. 31. 31. 36, Location 3 0 56 112 168 224 LSD .05 1,050 1,440 1,860 2,000 1,700 300 67.7 57.5 52.8 57.6 61.1 NS 7,010 8,190 9,550 11,430 10,130 NS NS Not significant at the 0.05 level of probability.

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136 Table 4-12. Recovery of applied nitrogen in 'Pensacola' bahiagrass forage and stolon root systems as influenced by rates of N at three locations. N Rate Forage N Yield Stolon + Root N Yield Total Plant N Recovery of Applied N kg ha ^ Location 1 kg ha -1 dag kg 0 56 112 168 224 30 80 100 120 120 8 9 5 5 7 38 89 115 135 137 91 59 5S 44 Location 2 0 56 112 168 224 30 60 80 80 100 4 7 6 7 7 34 6 7 86 87 107 59 46 32 33 Location 3 0 56 112 168 224 30 50 60 80 100 5 7 8 9 10 35 57 68 89 110 39 29 32 33

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137 Blue (1977, 1983) in that 40-50% recovery occurred at the lower N rates and decreased with increasing rates of N. The high apparent recoveries at location 1 are probably the result of cattle fecal residues absorbed from previous years as the stocking rates on the site were much greater than at the other locations prior to year of treatment. Larger amounts and distribution of rainfall at location 1 could have attributed to increased recovery of N by developing more massive stolonif erous root systems to capture applied N. The work by Blue (1977) and Beaty et al. (1964) showed recoveries ranging from 40-50% for the first 4 years, increases to approximately 70% during the subsequent 6 years (Blue, 1966, 1974) The increased recovery was attributed to the ultimate development of a massive stolon root system which is capable of absorbing relatively quickly a large amount of N which is stored in the stolons. Beaty et al. (1964) also demonstrated that stolon-root mass of bahiagrass increases with increasing rates of N. Apparently there is a large potential for N to be utilized and immobilized in the development and maintenance of stolon-root systems. Dry matter yield increased to all levels of N when sources of N were averaged over all locations. As reported earlier, source of N had no effect on overall DM yield at any location. The important aspects of forage production for a producer are the amount of forage produced per kg N applied and the cost of producing that forage (Table 4-13) For the first 56 kg increments of N both anhydrous ammonia and ammonium nitrate cost approximately the same. This is due to the fixed application fee for the anhydrous ammonia. As N rate increases, due to the price difference kg ^ of N applied, the anhydrous ammonia becomes less expensive than the ammonium nitrate. Also, the efficiency of

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138 n H c 0 £ cd CO o — >, JZ c [fl e o — — cu u o re cu M c Sj o 14-1 [fl CO cfl r4 60 cfl •H • z [fl CH c cfl CO H a o 4-4 CJ cC cfl M m c M CU 3 CH O *4-l 4J o 4-1 a n 4J 0 Cfl 0 5-4 4-1 H c d Cfl £ >, 3 a •H c (3 a) c H o H ^4 '4-1 M U4 o CO O U C CU B cu CJ CO o Z J (-4 o< o cu < Ch o. z s Q 00 C cu oo^o cu (J IT) (4 u a o S-i c cu m h a, 01 Cfl 0 U cj 60 cfl S (J Q O 4J CO 0 U Cfl cd C4J 2 cfl xi c o c 3 o o o O in CO — vO m in o O o o o o o o LO I-. o rH ro CM ro o in H o c c O CO o o o O EE i z m o CM H rH CM CM H 1 cct 1 CO co LO rH XI 1 CM CM CO O o o C CO O c o C EE l Z 1 . CO o vO CN CO
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139 forage production (kg forage kg ^ N applied) decreases as N rate increases to 224 kg N ha \ The first 56 kg N ha ^ produced the most forage kg ^ N applied (40 kg forage kg ^ N) This efficiency is consistent with that of other researchers (Beaty, 1964; Blue, 1966, 1974). A producer should evaluate his own needs for forage production ha ^ and compare costs and benefits when developing a N fertility program. The data in Table 4-13 would suggest that a single yearly application of 56 kg N ha ^ of either anhydrous ammonia or ammonium nitrate or 112 kg N ha ^ of anhydrous ammonia would produce the most economical and efficient forage yields of bahiagrass. Close grazing or clipping will provide more total forage and better utilization and adjusting stock rates to allow maximum utilization would produce forage of higher nutritional quality. Regression equations and correlations for the affect of N rate on nutrient concentration and content are found in Tables 4-14 and 4-15. Conclusions The objective of this study was to determine the effect on anhydrous ammonia versus ammonium nitrate as sources of N on the yield and chemical composition of bahiagrass forage. No differences in DM yield were found due to source of N in this study. Nitrogen, IVOMD, and P concentrations increased with increased rates of N and were greater when ammonium nitrate was used as the source of N. Concentrations of all nutrients increased with increasing rates of N. Phosphorus and Cu were found to be deficient in forage at all rates of N for providing NRC requirements for an average milking 450 kg beef cow. The ultimate objective of pasture fertilization is to

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140 'S. QJ JZ "3 'J 14-1 CO ~j rH o T1 4 m r* —• n\ \U CJ c 0 u U (3 CJ H 3 a o oo CO n fo 0} w CO h bO cfl rl £ cd JD M £o (3 o •H 4J crj 3 cr CJ C 0 •H CO w 01 -l C£ CJ CM C*i o c o "rl 4J CO CJ o c 0 •H u CtJ a o 03 C o H a cr w e o •H CC CO a bC a) r>3 c o cj cr W c o ri a tn CJ Sj M 01 C cu a) r-l c CO CJ -rl D. U 0J CO a > M CO cd T3 OO O CO CN| O X O CO o o o o + + CM t — I CO I— I vO i — It — I vD • -CO • 00 CO O-HOOZOCMZ II II II II >< >< >< >• II II CT> iH CM O M i — I CM I i — It — It — I I | | I I o o o o o X X 2 S M o

PAGE 148

141 CM c o •H n> TO 3 — c o •H W is, <3i U od 0) OS EN PS o •H 4J id cr W c o •H ca CD CU M bO 01 C 0) CD i-H -d xi C TO (U -H 0) TO Q > 60 to TO CN CM ci cm o o o lilt i i i i X CN + X X CM CM CM o o O O •CO o X o 00 i 1 + W H fl Oi o m cm X o o + m • • C/3 CO [/) W C/l OcMrH2<32222 II CM I 00 * >^ CM 00 + X in in o o o o + CO CO o 2 TO 00 > 2 Q 2 i*5 O 2 M O cd ,fi >> H SB •H rH 0 H ,C TO CM o CM r-l & T3 c cd o 1 — 1 00 o > rH cu i — i CM in rH o rH o CJ JS HI o HI id II HI X c td a ii •H HI HI to H M c tc SB •H Cfl T3 QJ HI X) o o 2 O II li CO X 2

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142 cm c o •H 4J CCj 3 cr w C o •H to en a) t-i co 0) 0 H *J ca 3 cr in c o H [0 00 HI M) aj 0) 4-1 G ty rH X) £> C cd d) -H Du U co CM o r->. CM CM O O o + CM X CO CO o o + CM X r-~ H O o o •CO C X m + I X in o •CO rH X LO + I H X CO oco I Id 00 m \a • COCMrHrHrHOOlTlOI X CM CM •CO O X vC + I w vo trt i/i II II II II 1! II II >H >^ >• >-• CO ON CO o cyi C-l rH H CM H CM rH rH X O O O o O o o CO CM •K XCM CM CM X X — I CM m o rH O O O I o I X I 00 X • X co o in m -l P-i £>-4 X I '-O CO CO f CM X in H o c 1 X o CM o + in X in H O O o I x in m o + o c i II EH c; X m o o o c I o\ rH o + CO rH II X w cc H <• I X rH o f m id S S Q O 2 Cd O 00

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143 CM at c o >H JJ cd 3 CT W 3 0 •H CO 0} 01 n 60 U CN OS s 0 •H *J Tj 3 cr W 3 o •H CO CO 01 M CU K C 01 0) rH £ cd 01 -H a. m oi cd a > XI 60 CO 00 H CN rH co CN O o O • o I I I I co X co co X! o rH o rH O o • o o O + I + CN CN X X cn io m X co o 00 • O n id ^ CO CN CN CO O O O O CO X r-O o o o + CN X CO CN a i X X X X X X in oo X Cl c o-. CN rH CO H H CN O o CO rH o + + c o o + + + + + in >* in H r> VD m CN — t o> rH CN rH CN CO rH ON H (H 5H t X >< S S CO 60 p o z px, x u a m XI 4J 53 H rH 60 •H X cd rH D rH CN in rH o H o
PAGE 151

144 maximize profit per unit land area, usually through the production of some animal product. The recovery of N was mostly in the 30-60% range except at one location where 91% of N applied was recovered at the 56 kg N ha ^ rate. Recoveries of N decreased as N rate increased. The most economical and efficient forage yields were obtained with one yearly application of 56 kg N ha 1 of either NH^ or NH^NO^. If additional forage is needed, then a single yearly application of 112 kg N ha ^ as NH 0 would be the most economical.

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CHAPTER 5 ACCUMULATION OF DRY MATTER AND NUTRIENT UPTAKE OF TROPICAL CORN, GRAIN SORGHUM, AND FORAGE SORGHUM Introduction Increase in dry weight is a useful definition of growth for those interested in crop productivity. Knowledge of dry matter (DM) production and nutrient uptake and distribution is needed to relate to plant growth and development (Jacques et al., 1975). Crop growth is usually more accurately characterized by measurement of dry weight than measurements of fresh weight, which can be strongly influenced by prevailing moisture conditions. Dry weight increase has been described mathematically as a function of physiological, pheno logical and environmental factors. Increase in dry weight with time is usually characterized by a sigmoidal curve (Leopold and Kriedemann, 1975), in which three primary phases are recognized: expansion, linear, and senescence (Richards, 1969). In the expansion phase, the growth rate (increase in dry weight per unit of time) is initially slow but the rate increases continually as more dry weight is added. Accumulation of dry weight is exponential until self-shading or other conditions prevent the increasing leaf area from producing a proportionate increase in the weight of the plant (Watson, 1958; Leopold and Kriedemann, 1975; Duncan et al., 1967). The end of the expansion phase marks the beginning of the linear phase in which the increase in DM continues at a constant rate. The final, 145

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146 senescence phase is characterized by a decrease in growth rate as the crop approaches maturity and begins to senesce (Salisbury and Ross, 1978). The patterns of growth and DM distribution observed in tropical corn ( Zea mays L.) (Goldsworthy and Colegrove, 1974) suggest that the capacity of the grain sink to accommodate assimilate can limit grain production. McPherson and Boyer (1977) pointed out that a potentially serious problem occurs if sink size has been affected by low leaf water potential. Moss (1962) and Allison and Watson (1966) have shown that when grain sink is missing, DM that would have been translocated to the grain accumulates in the stem and husk. Yamaguchi (1974) stated the low grain yield of typical tropical maize is due to short growth duration caused by high temperature, rather than low CGR or low productivity per unit growth duration. ... In the typical tropical maize, leaves die quickly after silking and the duration from silking to harvest is short, hence the leaf area duration (LAD) is smaller. The reason for this characteristic is unknown, but it seems that high temperature is one of the important factors since the senescence of the leaves of tropical maize in highlands and in lowlands in winter is slow where temperatures are low. The grain production per unit of LAD (G/LAD) of tropical maize is large. In other words, the efficiency of green leaves for producing grain is not at all low. Therefore, the small LAD may perhaps be one of the yield limiting factors of typical tropical maize. ... In tropical maize there is a loss of total dry weight (TDW) with approaching maturity. There is usually no such loss in temperate maize. Significant loss of stem weight is only reported from the temperate area by defoliation at silking. As this loss was also observed in tropical highland maize this characteristic may be genetic. The probable explanations for this TDW decrease are (i) respiratory loss from the stem and husk, which can not be replaced by the current assimilates or (ii) more probably, translocation to the ear of materials previously held in the stem; this process is accompanied by a rapid respiratory loss in the stem.

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147 The harvest index of typical tropical maize is 0.38, which is smaller than the 0.5 or more of temperate maize. This index is also low in tropical highland maize (0.39). Thus, it appears that this character is also genetic. The length and dry weight of the culm of tropical varieties continued to increase after silking. This growth of the culm after silking may compete with the growth of the ear and result in a low harvest index. -2 The number of kernels m of tropical varieties was about 2,600 regardless of the climatic conditions within the limits of this experiment. This number is much smaller than the 4,000 kernels m or more reported as high yields in temperate varieties. This difference is mainly due to the difference in number of kernels per ear. In tropical highland maize, this small number was compensated for by a large kernel size and produced a high grain yield. Nevertheless, the evidence reveals that the grain yield of tropical maize is more frequently limited by the sink size (kernel number) rather than the source of photosynthates It should be mentioned here that the various characteristics of tropical maize described above may be interrelated, for example, LAD and the number of kernels. Thus, it is difficult to state which is caused environmentally or genetically. However, at least some of them are under genetic control. In other cereals, for example, in rice, improvements of plant traits have succeeded in increasing the yield ability of tropical varieties. These facts suggest that varietal improvement is definitely one of the important approaches for obtaining high yields of tropical maize. (p. 77) Some investigations have measured the inorganic nutrient uptake by corn and sorghums ( Sorghum bicolor L. Moench) It has been recognized that amounts of most nutrients removed by a crop harvested for silage may be much more than when the same crop is harvested for grain (Hanway, 1966). A considerable range in values can be expected for each element, since soil drainage and fertility, climatic conditions, plant population, crop species and genotype, and fertilizer practice can influence crop content of each element (Fribourg, 1974). Work by Benoit et al. (1965) and Owen and Furr (1967) showed little difference in the

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148 mineral nutrient content of corn and grain sorghum, except for K, which can be influenced by fertilization. Fribourg et al. (1976) reported the results of inorganic nutrient uptake by corn and sorghums. The amounts contained in the above-ground plant parts exhibited considerable range: 34 to 220 kg N ha ; 8 to 34 kg P ha" 1 ; 31 to 271 kg K ha" 1 ; 8 to 55 kg Ca ha ; and 9 to 45 kg Mg ha" 1 Since the quantities removed are the products of harvested plant part weights and percent composition, they are influenced not only by the climatic, edaphic, genotypic, and management considerations, but also by soil nutrient availability. Growth and DM production in grain sorghum have been reported by several workers. Vanderlip and Reeves (1972), who defined 10 growth stages of grain sorghum from emergence to physiological maturity, suggested that by using those stages as standards the timing of sampling or treating sorghum could be described accurately in relation to the morphological or physiological age or status of the plant. They reported that the general pattern of DM accumulation was the same for different grain sorghum hybrids and that late maturing hybrids tended to be heavier at each stage of development than did earlier maturing hybrids. Jacques et al. (1975), in studies of grain sorghum hybrids, found that Ca and Mg uptake preceded DM production, and Ca was generally taken up more rapidly than Mg during vegetative growth. When vegetative growth had been completed, more than half of the plant's total Ca and Mg uptake had occurred. Whole plant nutrient concentrations decreased through most of plant growth. Zinc and Ca concentrations did not decrease as much during grain development as during vegetative growth. Lockman (1972a, b) reported that soil acidity, soil fertility,

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149 stage of growth, variety, and climatic conditions affected the mineral composition of grain sorghums. Jacques et al. (1975), found that 20 to 30 days after emergence sorghum plants began to grow rapidly; their dry weight increased faster than nutrient accumulation, and thus concentrations decreased. Hanway (1962b), found that differences in soil fertility influenced the amounts of N, P, and K taken up by corn plants, but did not markedly change the seasonal pattern of uptake and distribution of these elements in the plants. The content of N, P, and K in corn and grain sorghums was linear in relation to DM accumulation (Fribourg et al. 1976; Hanway, 1962c). The objective of this study was to measure the DM accumulation, nutrient concentration, and nutrient content of three genotypes: tropical corn, grain sorghum, and forage sorghum. Materials and Methods The study was conducted during 1984 at one location utilizing Pioneer Brand 'Y0M06 1 tropical corn, DeKalb 'EXA 816' tropical corn, Pioneer Brand '923' forage sorghum, and Pioneer Brand '8222' grain sorghum planted into 15-year-old bahiagrass ( Paspalum no ta turn L. Flugge) (c.v. 'Pensacola') sod. The genotypes were planted on May 30, 1984, on an Arredondo fine sand (loamy, siliceous hyperthermic Grossarenic Paleudult) Other methods and materials for this study were identical to those cited in Chapter 2 with the following exceptions Corn was planted at 45,000 plants ha" 1 and the forage sorghum at 130,000 plants ha and the grain sorghum at 75,000 plants ha" 1

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150 All plots were harvested at 15 day intervals beginning 30 days after planting through grain black layer. Harvest dates were June 30, July 15, July 30, August 14, August 29, and September 13. Seven plants were sampled in the corn plots for the first two harvests and then five thereafter. Four 1-foot sections of row were sampled for the first two harvests for the grain and forage sorghums with seven plants sampled thereafter. All sampled plants were weighed for fresh weight and moisture determination. Samples were dried at 60-70 C in a forced air oven. All samples were then ground in a Wiley mill to pass a 1 mm stainless steel screen and stored in air-tight plastic bags until further analysis. Results and Discussion Dry matter accumulation was slow during initial growth, then from approximately 60 days after planting when the plants were in bloom, growth began a linear phase (Figure 5-1) as described by Richards (1969). The two tropical corn hybrids ('Pioneer Y0M06' and 'DeKalb EXA 816') reached physiological maturity at 85 days, at which time DM accumulation started to decline. Moisture did not appear to be limiting until near physiological maturity (Table 5-1). The 'Pioneer 923' forage sorghum and the 'Pioneer 8222' grain sorghum continued to accumulate DM through the final harvest at 105 days after planting. At bloom, approximately 20 percent of the total DM had accumulated approximately 58, 30, and 45% of their DM, respectively. Dry matter accumulation appeared to be nearly linear following bloom of each genotype. At physiological maturity, the corn hybrids lost DM rapidly as the plants started senascing. This accumulation followed

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151 39 36 33 30 27 24 2. 21 1 8 15 1 2 9 6 3 A-'Pioneer 923' Forage Sorghum -'Pioneer 8222' Grain Sorghum 4Pioneer Y0n06' Corn -'DeKalb EXA 8 1 6' Corn 30 45 60 75 90 105 Days After Planting 1 20 Figure 5-1. Effect of days after planting on the DM accumulation of four cultivars of tropical corn and sorghum.

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152 Table 5-1. Rainfall data during 1983-84 at three locations where tropical corn, grain sorghum, and forage sorghum were planted into bahiagrass sod. Date Location — mm -D/ ID J/ ZU _>/ /j 30 c /on J/ JU 76 C 1 c b/5 6/10 8 6/15 41 6/20 8 6/25 7.', 6/30 7/5 7/10 89 7/15 7/20 7/25 76 7/30 18 8/5 38 8/10 8/15 18 8/20 51 8/25 8/30 9/5 10 9/10

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153 that observed by Hanway (1962a) on corn, and Jacques et al. (1975) for grain sorghum. Jacques et al. (1975) found that nutrient uptake preceded DM production, because the nutrients were required for growth and DM accumulation. More than half of the total nutrient uptake occurred before maximum vegetative DM was produced in grain sorghums. Vanderlip and Reeves (1972) reported that the general pattern of DM accumulation was the same for different sorghum hybrids and that late maturing hybrids tended to be heavier at each stage of development than did earlier maturing hybrids. Shipley et al. (1971) reported that in irrigated grain sorghum DM production was slowest from emergence to the six to eight leaf stage and from bloom to milk and was most rapid during the earlyto late-boot stage. Lane and Walker (1961) reported that applying N and P resulted in a faster growth rate and plants of larger size and dry weight. Organic matter concentrations for all cultivars tended to follow similar trends in that there was a rapid increase in OM concentration in the early vegetative stages and then the concentration stabilized near bloom for all cultivars (Figure 5-2) Organic matter accumulation followed DM accumulation for each genotype. Nitrogen and K concentrations increased rapidly during the first 30 days after planting and decreased thereafter (Figures 5-3 and 5-4). Since total DM varied with each genotype, total N uptake also varied. The forage sorghum accumulated 265 kg N ha 1 which was approximately 60% more uptake than was applied. The variety 8222 grain sorghum, Y0M06 corn, and EXA 816 corn accumulated 160, 140, and 90 kg N ha" 1 respectively (Figure 5-3). Potassium uptake was fairly constant after bloom for 'EXA 816'; however, K accumulated almost linearly in the

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154 I 10 100 90 110 TO (n) ft-'Pioneer 923' Foroge Sorghum D-'Pioneer 0272' Groin Sorghum k -Pioneer YOMOG' Corn -'DeKolb EXA 0 I 0' Corn 15 30 45 60 75 90 Days After Planting 105 120 39 36 33 30 27 24 2 2. E 10 o '5 i ? 9 6 3 (b) A-'Ploneer 923' Forage Sorghum a-'Pioneer 8222' Groin Sorghum A-'Pioneer Y0M06' Corn -'DeKolb EXA 0 I 6' Corn 15 30 45 60 75 90 Days After Planting 105 120 Figure 5-2. Effect of days after planting on the OM concentration (a) and content (b) of four cultivars of tropical corn and sorghum.

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155 5 I i 1 1 1 — 1 1 a -'Pioneer f oroge Sorghum -'Pioneer B222' Groin Sorghum A-'f'ioncer Y0M06' Corn -'OeKolfj f "XA 0 I 6' Corn a 0 l L 1 , 15 30 4b 60 75 go !0'5 120 Days Alter Planting ?ooi — i 1 r Days After Planting Figure 5-3. Effect of days after planting on the N concentration (a) and content (b) of four cultivars of tropical corn and sorghum.

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156 0 6 0 5 0 4 P 03 T3 0 2 0 I (o) 0 0 l 5 A-'Pioneer 923' Forage Sorghum -'Pioneer 0222' Groin Sorghum A 'Pioneer Y0M06' Corn -'DeKalb EXA 0 1 6' Corn 3 0 45 60 7S 90 105 120 Days After Planting I 20 100 60 60 40 20 I 1 1 1 1 r(b) A-'Pioneer 923' Forage Sorghum -'Pioneer 8222' Groin Sorghum A-'Pioneer Y0M06' Corn OeKalb E XA 8 I 6-' Corn 15 30 45 60 75 90 Days After Planting 105 120 Figure 5-4. Effect of days after planting on the P concentration (a) and content (b) of four cultivars of tropical corn and sorghum.

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157 other three cultivars (Figure 5-4). Sayre (1948) reported that trends in N accumulation are similar, though not identical, to DM production. In their experiment, N continued to accumulate in the grain as long as the plants were sampled. This indicates that N moved from the other tissues of the plant. Lockman (1972b) indicated that K levels in grain sorghum plant samples decreased almost linearly with age. Dry weather appreciably decreased relative K levels in seedling samples in one year of his study. Anderson et al. (1985) stated that the response of corn to increase N fertility differs considerably. Some experimental hybrids show increases in protein content and/or grain yield as N rates increase (Kamprath et al., 1973; Warren et al., 1980; Nelson, 1956). Several reports indicate that source-sink relationships are important in the accumulation and distribution of N and DM. Kamprath et al. (1982) found that low N uptake in corn before silking was associated with a low harvest index. Hanway (1962b) stated that the pattern of N accumulation by plants is influenced by the seasonal pattern of N availability in the soil. Seasonal pattern will vary with different times and methods of application of N fertilizer and the rate of mineralization of N from the soil organic matter will vary among different soils and different seasons. Potassium accumulation in Hanway 's (1962c) study continued until a later stage of maturity and there was no loss of K from the plants during the latter part of the season. Similar results occurred in the sorghum cultivars in the present study, but the corn hybrids did lose K after physiological maturity which is in agreement with Sayre' s (1948) data. Phosphorus ranged from 0.35 to 0.45 dag kg" 1 at the first harvest among the cultivars. The concentration of P declined rapidly due to a

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158 dilution effect by the second harvest and remained fairly constant thereafter (Figure 5-5). Phosphorus content increased through final harvest in both sorghums, but decreased in the corn hybrids after physiological maturity. Bates (1971) observed that the pattern of nutrient content with age varies with the species and with the nutrient. Phosphorus concentration with age is probably due to both a changing nutrient content of a given tissue with age, such as an increasing proportion of stem and a decreasing proportion of leaf tissue. Hanway (1962c) found that the P accumulation pattern was similar to the DM accumulation pattern except more rapid early in the season. Calcium and Mg concentrations reacted similarly for corn and sorghum. However, concentrations were higher for the two sorghums than for the tropical corn hybrids (Figures 5-6 and 5-7) Calcium accumulated more rapidly than Mg and accumulated to a greater level in the sorghums than the corn hybrids. Also, more Ca than Mg was accumulated by all the cultivars. Jacques et al. (1975) found in sorghums that Ca and Mg uptake preceded DM production, and Ca was generally taken up more rapidly than Mg during vegetative growth. When vegetative growth had been completed, more than half of the plant's total Ca and Mg uptake had occurred. In one study, Lockman (1972a) reported that seasons affected nutrient levels in grain sorghum and that dry years caused high Ca and Mg, as well as other nutrients, in sorghum leaves, probably because K would be less mobile in the soil. Fribourg et al. (1976) stated that, in general, nutrient uptake of N, P, K, Ca, and Mg increased linearly with increasing yield of either crop genotype used. However, grain sorghum above-ground plant parts tended to contain

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159 (n) a -'Pioneer 923' forage Sorghum n-' Pioneer (irnin Sorghum a Pioneer Y0n06' Corn -OeKolt) EXA 0 1 6* Corn Figure 5-5. Effect of days after planting on the K concentration (a) and content (b) of four cultivars of tropical corn and sorghum.

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160 S3 o u 05 0 4 0 3 0 2 0 1 (a) ^-'Pioneer 923' Forage Sorghum Pioneer 8222' Grain Sorghum A-'Pioneer YOMOG' Corn -'OeKalb E X A 0 16' Corn l 5 JO 45 ()0 75 90 Days After Planting 105 120 c JZ Jr.' a u 60 50 40 30 20 1 0 (t) ) A-'Pioneer 923' Forage Sorghum -'Pioneer 8222' Grain Sorghum APioneer Y0ri06' Corn -'DeKolb E X A 8 16' Corn 15 30 45 60 75 90 Oays After Planting 105 120 Figure 5-6. Effect of days after planting on the Ca concentration (a) and content (b) of four cultivars of tropical corn and sorghum.

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161 X o n E 0 5 0 4 0.3 0 2 0 I (nj £>-'Pioneer 923' Foroge Sorghum -'Pioneer 0222' Groin Sorghum A-'Pioneer Y0M06' Corn -'OeKolb E X A 0 16' Corn 30 45 60 75 90 Days After Planting 105 120 I 20 (b) I 00 00 I a JZ CT> 60 E 40 20 A-'Pioneer 923' Forage Sorghum -'Pioneer 0222' Groin Sorghum APioneer Y0M06' Corn -'OeKalb E X A 8 16' Corn I 5 30 45 60 75 90 Ooys After Planting 105 120 Figure 5-7. Effect of days after planting on the Mg concentration (a) and content (b) of four cultivars of tropical corn and sorghum.

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162 larger amounts of the five nutrient elements at the lower yield levels than did corn at the lower yield levels. Iron concentration was very eratic at all harvest dates. As with other nutrients studied, Fe concentrations were highest during the early vegetative stages then reduced due to a dilution effect by very rapid DM accumulation between' 30 and 45 days after planting (Figure 5-8). Accumulation of Fe tended to increase in the two corn hybrids until black layer formation in grain. The Fe continued to increase in both sorghums through the final harvest at 105 days after planting. Soil contamination of plant samples could explain the eratic nature of the Fe concentration in the various genotypes. Jacques et al. (1974), comparing washed with non-washed samples, showed that no valid inferences about Fe in blade and sheath tissue, and possibly head tissue, could be made if samples were not washed thoroughly. However, significant differences between washed and non-washed samples were found for Mg, Ca, Zn, Cu, or Mn content in any plant part. Manganese, Cu, and Zn followed similar trends in concentration and content (Figures 5-9, 5-10, and 5-11). Manganese concentrations ranged from the first to final harvest from 87-34, 83-47, 72-37, and 46-40 mg kg" 1 for '923', '8222', 'Y0M06', and 'EXA 816', respectively. Jacques et al.,(1975) found whole plant nutrient concentrations decreased through most plant growth. Zinc and Cu concentrations did not decrease as much during grain development as during vegetative growth. Nutrient uptake generally had reached 50% or more of total uptake in the plants when they completed vegetative growth. Nutrient uptake preceded DM accumulation. These same trends were true in the current study for Mn, Cu, and Zn.

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163 260 240 220 200 100 I 60 I 40 1 20 1 00 80 60 40 2 0 (o) G-'Ploneer
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164 1 601 < 1 1 A-'Pioneer g23' F jrage Sorghum 140 o-'Pioneer 0222' Groin Sorghum A-'F'ioneer Y0n06' Corn -'DoKolb EXA 0 16' Corn I 20 20 1 1 1 I L_ J 15 JO 45 60 75 90 105 120 Days After Planting i 5 0 5 1 1 T (b) T T 1 1 T 1 -Pioneer 923' Foroge Sorghum 0 -Pioneer 8222' Groin Sorghum Pioneer Y0MQ6' Corn DeKoltJ EXA 8 1 6' Corn i i i i 15 30 45 60 75 90 105 120 Ooys After Planting Figure 5-9. Effect of days after planting on the Mn concentration (a) and content (b) of four cultivars of tropical corn and sorghum.

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165 Figure 5-10. Effect of days after planting on the Cu concentration (a) and content (b) of four cultivars of tropical corn and sorghum.

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166 50 -10 30 — i(a) 20 I 0 A-'Pioneer 923' Forage Sorghum a 'Pioneer 0222' Groin Sorghum A Pioneer YOrlOO' Corn -'DeKelb E X A 0 I 6 Corn 5 0 45 60 75 90 I05 I20 Days After Planting a c in 0 6 0 5 0 4 0 3 0.2 0.1 0 0 A-'Ptoneer 923' Forage Sorghum -'Pioneer 8222' Groin Sorghum A-'Ploneer YOriOG' Corn -'OeKolO EXA 8 16' Corn 105 120 Ooys After Planting Figure 5-11. Effect of days after planting on the Zn concentration (a) and content (b) of four cultivars of tropical corn and sorghum.

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.167 The yield and agronomic characteristics for the sorghum and corn hybrids are found in Table 5-2. The nutrient concentration and content for each element or nutrient at final harvest are found in Tables 5-3 and 5-4. By the final harvest, the sorghums removed more N and K than was applied (Table 5-4). Fribourg et al. (1976) found similar occurrances in corn and sorghums where both crops contained larger amounts of N and K than had been applied as fertilizer, indicating that soul sources of available K and N were utilized by the crops. The fertilizer N applied in the Fribourg et al (1976) study was less than the N uptake in many cases when N was applied at 135 to 170 kg ha Conclusions Dry matter accumulation and OM concentration and content increased rapidly after 30 days post planting. Nitrogen, P, K, Ca, Mg,Fe, Mn,Cu, and Zn concentrations increased rapidly during early vegetative growth and decreased rapidly thereafter. Iron concentration tended to be erratic throughout all harvest dates. The concentrations of N, Ca, Mg, Mn, Cu, and Zu were higher in the sorghum than in the corn hybrids. The other elements studied tended to be higher in corn hybrids. The nutrient uptake tended to follow DM accumulation particularly after the early vegetative stages of growth. Because environmental conditions do vary over short periods of time they will affect the validity of plant analysis if they alter the nutrient concentration at sampling, whether or not they alter any critical concentration. A number of authors reporting year-to-year variation in nutrient content have considered weather as a major cause (Bates, 1971). As noted, Fribourg et al. (1976) stated that since quantities removed are the products of

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171 harvested plant part weights and percent composition, they are influ enced not only by the climatic, edaphic, genotypic, and management considerations, but also by soil nutrient availability.

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CHAPTER 6 SUMMARY AND CONCLUSIONS Florida is a grain deficient state with many thousands of cattle shipped out of the state each year for stocking or finishing in western ranges or feedlots. Florida currently ranks 9th in the nation in beef cow/calf production. There are also some 3 million acres of bahiagrass ( Paspalum notatum Flugge) sod which might be more fully utilized in row crops and forage production. Several feedlots in the state are in need of good quality grain for profitable beef production. At the current time there is substantial freight costs incurred for shipping grain from the midwestern United States to utilize in cattle and poultry rations in the State of Florida Tropical corn or grain sorghum planted in the summer in multicropping systems could take us a long way toward meeting the demand for high energy feed grains by feedlot operators. This multicropping or intensification of land and resources is needed for Florida farmers to adequately compete and stay in business. The adage is no longer, "How much can I produce?" but "How much can I produce profitably?" If summer planting of corn or grain sorghum were feasible, this could add to our economic base and maximize use of our farm resources and management. Also, a bahiagrass sod, under two tillage systems, has served as the soil conservation component during the late fall and winter months, while in late summer it seems to serve as a trap crop 172

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173 for unutilized fertilizer under high soil fertility and possibly as a competitor for nutrients when soil fertility is low. Poor rainfall distribution and soil types which have low water holding capacity are a major detriment to high crop yields. Thus, many farmers have severely reduced corn acreage on non-irrigated land and many have incorporated irrigation into their management plans. However, irrigation is expensive, with a cost of approximately $4 to $6 per ha The Florida Crop Reporting Service reported the following results for the 1983-84 growing seasons. The area planted to corn in 1984 totaled 101,250 ha, 49% more than 1983 when many growers participated in acreage reduction programs. Of the total ha planted, 85,050 were harvested for grain, 72% more than the year before. The average yield was 3450 kg ha which included irrigated as well as non-irrigated land. Drought damage to late corn that was not irrigated was the primary cause of the yield reduction as most of the early crop and irrigated corn produced good to excellent yields. The value of the corn produced for grain was placed at $41,633,000, up 34% from the year before. One objective of this study was to determine the effect of anhydrous ammonia (NH^) as the sole source of N when tropical corn (Zea mays L.) was no-tillage planted into bahiagrass sod. Nitrogen is the largest and probably the most expensive fertilizer components used in producing corn, grain sorghum ( Sorghum bicolor L. Moench) and bahiagrass forage with NH^ being one of the least expensive sources of N available The tropical corn showed a response to the 56 kg N ha ^ rate for grain, residue, and whole plant dry matter (DM) yields at two locations. The third location showed a significant increase for the yield

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174 parameters to the 112 kg N ha 1 fertilizer rate. There was a 250% increase for the corn grain to residue ratio over the control. Insufficient rainfall during the silking through ear fill period decreased grain yields more than residue yields. Also, grain yields were more depressed when the highest rate of N (224 kg ha "*") was applied. This is attributed to the physiological processes and the plants response to high levels of fertility under moisture stress. Grain, stalk, and whole plant DM yields increased linearly in response to increased levels of N fertility at locations 2 and 3, but were quadratic at location 1 for grain and whole plant DM yield probably as a result to moisture stress. The concentration of nutrients in grain varied with location and N fertility did not affect Ca, Mg, Fe, Mn, Cu, or Zn at locations 1 or 3. Nitrogen content of grain and stalks increased linearly at all locations. Grain yield kg N in the aerial portion of the plant ranged from 25 to 44 kg ha The N content of stalks responded the same as grain. The concentration and content of most other nutrients did not respond to N rate at any location or only responded to the 56 kg N ha ^ rate and did not increase above that rate. The analysis of diagnostic samples indicated that N and Fe were the only elements increased by N rate when youngest mature leaves were sampled at 40 days post emergence. Whole plant samples harvested at 40 days exhibited a change in nutrient concentration for N, Ca, Mg, Fe, Mn, and Cu to increasing rates of N. Ear leaf sampled at mid-silk showed an increase to N rate for OM and IVOMD. The concentration of N and P were lower than the CNL values recommended by Tyner (1946) for sufficiency levels in corn ear leaves. Only K met the CNL values recommended by various researchers (Anderson et al., 1985). Climatic

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175 conditions, soil fertility, or competition from the bahiagrass sod may have reduced maximum uptake of N and P. Nutrient concentration determined with these three sampling methods for use as predictors of grain yield indicate that N, Ca, and Zn were all well correlated with grain, stalk, and whole plant DM yield when the youngest mature leaf at 40 days was sampled. When the whole plant at 40 days post emergence was sampled, N and Ca were positively correlated with final yields with K being negatively correlated. Copper and Mg were also positively correlated with final DM yield when this method was utilized. When the ear leaf at silking was sampled, N and Ca were positively correlated and Zn negatively correlated with grain yield. Nitrogen, Ca, and IVOMD were positively correlated to stalk and whole plant DM yields. A second objective of this study was to determine the effect of NH^ as the sole source of N for grain sorghum no-tillage planted into bahiagrass sod. Grain sorghum DM yield for grain and whole plant increased at the 56 kg N ha ^ rate at two locations and to the 112 kg N ha ^ rate for the third location. All three locations increased in residue DM yield up to the 112 kg N ha rate. Sorghum webworm at location 2 and moisture deficits at location 1 had a greater effect on grain yields than on residue yields. As with corn, it was found that 224 kg N ha ^ reduced yields where moisture was deficient. Grain yield and whole plant yield averaged over the three locations were 560 and 342 dag kg ^ more than the control when 168 kg N ha ^ was applied. Grain N concentration increased to the 112 kg N ha ^ rate at location 1 and to 224 kg N ha ^ rate at locations 2 and 3. The grain concentration of P, K, Ca, Mg, Fe, Mn, Cu, and Zn were not affected by

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176 N fertilizer at any location. The concentration of nutrients in sorghum stalks increased with increasing rates of N fertilizer at all three locations. Whole plant N content was 39, 58, 74, and 87 kg ha from applications of 56, 112, 168, and 224 kg N ha respectively. Efficiencies of N uptake were 43, 38, 35, and 32 dag kg 1 for the 56, 112, 168, and 224 kg N ha" 1 rates. It appears that, in these experiments, concentration of certain nutrients, particularly N, in the youngest mature leaf at 40 days post emergence, whole plant at 40 days, and third leaf below the flag at bloom can all be used as good predictors of grain yield and whole plant DM. Whole plant analyses gave higher correlations for N and Ca than the leaf at 40 days to predict final yield of grain, residue, and whole plant DM. These diagnostic tools would also be invaluable to help in determining nutrient deficiencies early in the growing season so that additional fertilizer or other management methods could be applied so that fertility particularly N would not be limiting to yields. The third objective of this study was to determine the effect of NH„ versus ammonium nitrate (NH.N0„) as sources of N on the yield and 3 4 3 chemical composition of bahiagrass forage. No differences in DM yield were found due to source of N in this study. Nitrogen, IVOMD, and P concentrations increased with increased rates of N and were greater when NH, N0„ was used as the source of N. However, these differences 4 3 were small although significant. Concentration of all nutrients increased with increasing rates of N. Phosphorus and Cu were found to be deficient in forage at all rates of N for providing National Research Council (NRC) requirements for an average milking 450 kg beef cow. The ultimate objective of pasture

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177 fertilization is to maximize profit per unit land area, usually through the production of some animal product. The recovery of N was mostly in the 30-60% range except at ne location where 91% of N applied was recovered in the forage and stolonif erous root system. The 91% recovery was at 56 kg N ha" 1 Recoveries of N decreased as N rate increased. This study indicates that up to 168 kg N ha 1 could be applied at one time to obtain significant yield increases. The first increment of 56 kg N ha" 1 gave the most forage product per kg N applied (40 kg) and this would be sufficient if stocking rates were such that overgrazing was not a problem. The cost of either NH^ or NH^NO^ are similar at this rate. However, if additional forage is needed then there is a cost advantage by using NH^ if 168 kg N ha 1 is applied. The last objective of this study was to measure the DM accumulation, nutrient concentration, and nutrient content of three genotypes: tropical corn, grain sorghum, and forage sorghum. Dry matter and OM concentration and content increased rapidly after 30 days post planting. Nitrogen, P, K, Ca, Mg, Fe, Mn, Cu, and Zn concentrations increased rapidly during early vegetative growth and decreased rapidly thereafter. Iron concentration tended to be.erratic throughout all harvest dates. This could be due to contamination of plant samples with soil. The concentration of N, Ca, Mg, Mn, Cu, and Zu were higher in the sorghum than in the corn hybrids. The other elements studied tended to be higher in the corn hybrids. The nutrient uptake tended to follow DM accumulation, particularly after the early vegetative stages of growth. A number of authors reporting year-to-year variation in nutrient content have considered weather as a major cause (Bates, 1971).

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178 Fribourg et al. (1976) stated that since quantities of elements removed (content) are the products of harvested plant part weights and percent elemental composition, they are influenced not only by the climatic, edaphic, genotypic, and management considerations, but also by soil nutrient availability. Most field crop research is conducted utilizing irrigation as a management tool to insure that moisture does not become a confounding factor in the research project. However, the cost of irrigation is prohibitive for most commercial producers or the availability and quality of water may limit its use in some areas. The summer planting of tropical corn or grain sorghum might be an alternative for providing increased grain production for our grain deficient state. The years 1983 and 1984 were not typical in that the normal heavy summer rainfall turned into two back-to-back droughts in the months of August and September. Research needs to be continued to look for drought resistant, prolific, and high quality tropical corns and grain sorghums which might fit into this management regime. Also, the regrowth of sorghums and the residue of sorghums and tropical corn along with regrowth of bahiagrass from these multicropping systems would be desirable for the fall feeding of the beef herd. Nitrogen concentration of grain sorghum residues were consistently higher than that of corn while IVOMD values were lower in grain sorghum. Crop residues of grain sorghum and corn have attracted attention as an alternate economical forage resource for livestock utilization. There are few data available on agronomic production factors affecting yield and quality of crop residues (Perry and Olson, 1975). The time is here for economic evaluations of the most profitable multiple cropping systems. More research is needed to evaluate and

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179 adapt those systems which are most energy efficient. Soil fertilityplant nutrition and crop quality information, as these factors relate to cropping and/or tillage systems, will also need to be related to practical on-farm use. Florida's soils are among the most infertile in the United States and the development of year-round forage or cropping systems will require exact knowledge of element removals so that soil fertility will not become a limiting factor in crop production.

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APPENDICES

PAGE 188

APPENDIX A ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR TROPICAL CORN PLANTED INTO BAHIAGRASS SOD BY MINIMUM TILLAGE METHODS

PAGE 189

CO T" JUJ (-4GO cd *H r* A£ r J J CM 4_j •H T3 CO d) c (_} 4-J O C *H rd 4-* | n3 Dm CJ •H O QJ CO d) r-\ I. -1 f — — CO 4-J cu r^H O 03 i m 1 iu f i — *ri H C vj 00 0) £ 00 £ td nj | rH CO •H 3 4-J O cu 1 CJ O "O t-t ^ r— O •v* &0 C CO •H d) > 4-J O ctj i P-( rH 14-1 CO 4J cu rH O 3 C CO G QJ 3 i-4 r| 14H x; 4J C CO -H a. CU a) 4-1 CO Q a> rH •H T3 O O C/3 UJ a o r-. CM X X X -X X X
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183 •G 4-1 01 o E U co ro CN CNl vD in to E 00 CO CNl co co LT1 1 m cfl H 00 CO u 00 CS1 O o -cr CNl CM m rn CO c o •rH _l ON rH m c( CNl m co CO CN| a a P-, oc CN| -cr in ^£5 r-s cni oo vd r-r-m \D in o co r — tn f— i in l-H i— I rH CN] i — | I —
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184 00 in oo m m CN CN St m m m
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185 i — cd o CO 1 c c •H *H CO 0) oo o CTJ rH rH *H 1 o 4-1 c cd c rH i-t G. o QJ o i — ^ o o o *H •"O 4-J r— 1 S3 QJ U •H O > H i-i 4-J iJ Jb o - CO M CO J-4 1-4 00 C O cfl •H
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186 i — l O CO u 4J CM I CO c — • •H G O •H OJ CO 60 S-J co O H iH H 4-i 1 O c 4-1 C c <0 r-l co U CO tj co nj u u o oo C U-t CO •rH 00 •H CO CO 42 o 4J CO o C 42 CD •H O U 4-1 •H C C4-I -r-l 14-1 4-1 0) TJ c O CD 0) CJ 4J 6 o C 4-1 o C cfl CO O rH -4 o CO 4-1 'Jl c cfl CCJ rH o • — ( CO CO CO u u

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187 3 c G H 0) to cd cd j-j oo c •H cd u o ON m o rn o o I 0 c a u o o c c •H rH c3 QJ O •H 0 C (0 1 I D. QJ G 3> o o i-1 -u rt o CO cd u DO CO T3 M O .e C XI QJ •H O O 4J •h d a) x> o CD u .u C cd c o tH j-i C3 H CU O D U CO H o cd c ai E w a u H en 00 o o O O o o l < cd H id C a 6 u a ii H cd M o cd CO c cd i — ( c a o M cd jj CO C cd

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188 — c 01 J s c z i — 1 CO — , c 1 c •H ,Sli o 1— 1 CO Q -J (0 — i i — i •H u 1 \ 4-1 c C cO CO W r— 1 0 c nj O i — i •H &, — 1 o a c o >-J •H 00 65 4J c m CO •H r-H o r— ( o ,— j 0) 4J CO o — o 4J co a d cy j 3 to cO OJ cr (0 u H a cfl 0 c oo o co H •H 4J J3 C cd •^ H — S rt a) P M o 00 4-1 c c u •1-1 z CO Z co Z 1 > C r-1 H >, 4-1 z it H D. .11 1 — 1 Rl CO M C rH i-l a) 11 M H 1— 1 CM u-i co r-l u d O 0 0 td H CO s j-j -C co 4-1 z a O CO US, co z

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189 k CD rH -a H c cu E 2 4J re 1 — 1 cu •H M c H co ,a co is H — o re cu M 4-1 •H 1 co >, a •H CO oo re rH i — i re i — 1 Q 4J •H CO 1 o c c ^ U 4J C re CD o w — I a <*-i o CO >4-( CO 0) o 1 — 1 CT) a re •rH re oj > c CO o o M— 1 4-1 •H -H o c 6 4-1 re o re c o o o M rH re u re oo u c O TJ •H 4-1 o rH CO rH CO cu u CO C CO CO cu re H (j o oo •h re 14-1 -H a TD — ( cu re re a O XI u •H o o !>> o c -u o c H -H 4-1 c re xi •H rH cu a re CU 4J Q u u c 00 i-i re O rH u a, m ON o m 00 CO O in CO a z 3 o O O o c rH (3> >o vO 00 O m 33 oo 00 in M c O c O o o o o H n in o I o o co o o CO 2 CO 2 CO o o m n o r- O o CO co o 2 O o o o H
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190 jj (3 a) 2 _j 1 — 1 7*H u Q :f r — 1 z X n cd W 1 — | f., — i ni 4_) co rj i — | cd •H — | r— | > 0 c •H •H C H 0> •H 1 — \ — cO CO Q z O O 0 0 0 0 rH \ CO Q [O CO Z 0 O 0 0 0 0 rH r ^ j Q c 0 vC CO 0 Z O O rH o o co 2 o o O o o o 4-1 •H -a Xi 4-1 cn rH u rH 60 c 0) c Cfl O H 4-1 at 4-1 •H 00 M •H a c S 0 •H a rH CO rH >, J3 ClJ jj z cfl H o< -J rH CO H a rH 4-1 4J CX Q) II BO H rH 4-1 Cfl rH (3 V-i cfl a) O O ct) ct) H H £ M 4-1 rH CC z O O co CO (Xi W Z -X

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191 — H C > 3 C bC U en CO CO CO CO CO CO CO 25 23 25 Z Z z z 25 o o w [/] CO co CO CO co CO CO co z Z Z z Z Z Z Z z o 1 CO co o m CO to H o CO CO CO CO 2 Z Z 25 rH o O vD cc CO o z z O o H c CO w c Z z z co Z o o o o CO z o o CO z o o o c C4 cc) u a 3 Q g O H S > erf O m H

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192 H H P O > CO in I— 1 n as O M H

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193 H 30 c o H c u c c o u (3 u c o u n C •H B a CO C o o M 0 c a •H o •H u-i >4-l 0) c u G O •H 0) H o u B c pi, 00 cd 3 z z co Z Z O I o CO Z '.2 CO o I CO z CO Z CO O CO z • z o I co m co z • z o z z CO z 00 to m CO Z o a i C J i — i in LO Z O 1 1 m X o u-i ro 3 o O H O r. o Z — O O o o 1 — 1 m O o m oo o Z O O CO 3 Z o 3 -J •H i — I — I ^ — 0 S-i P. o a] > a en 3 a d a a H X I < 0 z (Tl H ^3 '3 CO fa a 3 O C S H H Z

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194 H 00 r-. lO CO o o PS to CO CO p 'J u 00 o i I CO Z CO z co Z CO z CO Z CO Z o o o CO z CO Z CO Z CO Z CO z co Z co z CO Z o o CO z CO z co z co Z CO z co z co Z co z o o CO z CO z 03 in CO z CO z co z CO Z O I CNJ CO u~l CO Z • Z o I co z CO Z co Z OA o o CO z CO Z CO z co z o o CO z CO' z CO z o o CO z CO z o o co H H .u H X) o G a > a> c a a) O a DC 0 z co z

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195

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196 o 31 — : O co O m o o -31 N O CN CN r— o 3 3 o O o o O O rH I < N 3 u c a to CO i — i Lfl o CO CO co co CO o -r; _, r^ ^ < Is IS Is 1 r o r 1 o 1 — '. CN rH o r^. CO U 1 CO CO o >^ • r i^-j it-* ,S IS IS Q 1 — 1 1 1 — 1 co CN o o O CO CO
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197 H Pi 3 o > 2 c C s 60 o CO B5 NS NS NS NS CO z CO z NS NS NS ON ON 00 CM ON CSI l-~ 3 ON CN CO CN] 'X) 3 00 X CN ON o o O 3 3 3 3 3 3 o oo on ON '3D CM ON 00 00 LO CO O ON a 3 o 3 H CO z 3 3 3 3 O ON 3 3 3 3 U CO cj 3 c N O > H Si H

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198 pt! H c > c c N 01 0) 00 oo CO C J 00 CO C J oo oo CM CO CM co in oo o ~ O o o o O O o a Ln on — j on NO 00 on 00 O-N — ; ON ON ON o o O o o o O o o O CO on m ON On CO on CO on CO 0> ON ON LO ON ON o o o o c o o o O o o rH ON 0> cc on LO ON 00 t— i On r-~ on cr. CO ON o o O o o o O O *— 1 ON CM ON o C7> On CO CM ON o o o o O O O rH oo on aZ O M H

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199 H H 3 Nl 3 U CO 53 u CO co ic r> >£> o rH rH oo CN 0> m m on CO rOS on o o o o o o o o o rH o r- o 00 CM m \P o -£) o 00 o o c o o o o O o rH est o> oo cr> CO CTN cc ON CNJ 00 o c o O c o o o o on Ol co rvO co o o o O O o o o o> ON on CO rn o o o O o O rH CN on o o o O o — 1 c o o ON o o o o ON o o o o o *4 cp UJ c s O H cd H

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200 H O > u CO o> CO co CO OA O M H

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201 H H P SS c > o c CM u c s: ON m 3> CN m CM CM vO vO r XI oo 2 3 • — ^ O Q — i Q 1 — J 3. .3 j ( 1 — 1 Q o> 5> 03 On 00 o> m ON 3 o 3' CD Q — i I — J Q f-J 1 — | CO -1 m on oo OS in 3 o 3 o O o c 3 — m rH on m i — in O 3> 3D oo 00 co 00 o 3 3 o a o o o 00 rn a> CN on o r00 r- o O o 3 o o i — i o> LI ~i cn o 00 oo oo X o o o o o o H 3 o 00 3 CO CO 0 00 1 — i O 3 3 3 c 3 1 — 1 1 — 1 ON m r-. CM CO 3 3 O 3 3 H 00 CO 00 3 3 0 3 — 1 0.86 1.00 o o a) 3 00 T. 01 C S3 3 3 C N 3 3 > H H

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202 i < H si H — CO CO o CO on ON CO z o a o O Q O o o o ON on rin C 00 00 C^ 00 CO 00 00 o 3 3 O o O a o o Q — o o co i-H O ON o o o m CJ m in in a o O a o c c o o 1— 1 3 U -J oo i — co On co CO o o a o o o o o 1 — 1 r ; 00 r i r> o o o o O o C o o n CO in CO co 00 o> CO o o a 3 O 3 — \ 00 CO U CO T 1 o :o CO 00 ON o O O o o 1 — I iH ON 1 1 o DO CO o C o 3 H CO o 00 CO o o o c o CJ u o CJ P-, CO o 3 3 3 3 ctj H p.. U 043 CJ a 3 a H a; H

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APPENDIX B ANHYDROUS AMMONIA AS A SOURCE OF NITROGEN FOR GRAIN SORGHUM PLANTED INTO BAHIAGRASS SOD BY MINIMUM TILLAGE METHODS

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ac a o u c • •rl CO c T3 O c 4J 4-1 N c to to o rH o D. i— 1 iH 0) •H 0) O U u tD .£ X> 4-> 3 CO 4-1 to O to c M -H i a c o •rl e & ^ oo OO 0) c o •H C 3 (D O 3 1 t— 1 CM rH UH O C CO CO rH 3 T> CO O CD CO U CO Xi 4J CO 4-1 CO CO a. CD U a) 4-1 00 Q tO rH tH •rl £ O CO CO XI H pq CD a) 4J rH CO .a n) H a 3 in Li-, 1 X m CM O 00 oo D in CM CM H rH rH SO 50 CN 0\ o CN 0 0 o CN I o 43 00 CN CN CN m o CN oo CI in OC o in 00 o c CO CN CN CN o CN iO CN CN CN CN O i o CM c O 00 CM m H in CN H m CM m oo m eg CM Oi CN CN
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205 c c CJ 00 CO u 0 o I — 1 o CN i — 1 VO vO VO vD a> CN co m o o 00 CO t-i CO r~ CO m co ro i i r-H — DO -CT a> CN r-> >o o co CO cn m 00 IT) IT) UO m m cn CO i— I co 1 — LI vO 1 — ~c co tH H — — iH 0> o-. in CN rH CN — CN J C> H CN — t— 1 — vjD co CN G CO CN CN CN C J CN o-n o\ vD in CN CO CN C 3> CN H H r-i — O r CO CO CO rH H i— 1 O H m CN CN CN CN CN — 1 iH H CN H O O o C O a 0 j c CN O
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206 ce J2 00 o c [xO m in i£3 CN CM CO O CXI co 3 0> o C c c c LO c z 7Z ro 60 E CO 00 CO co CN o CN LO CN IT) CM c o u c
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207 rH CO 4-1 in CO — c • o •H J-J rfl cd C3 s 3 X. GO U Q 0) 4J c C CO ( n) a 00 M • CO CJ o rH O O r— TJ 1 — 1 0) •H 0) 00 4J CO • 4J U o CB in 6 >> u T3 S-l c o H CO • M O 4-1 o c 0) H a •H U—l 4-1 a) d o a) o B o 4J o c • cfl O rH cu rH •H S-i 4-> C H cfl o rH -H z 0) 4J S-i cfl u u o o U i — 1 4-1 c CM ai 1 0 M rH 4J 1 cd H CO H M Z m oo c o in 0\ o o CO o o o o CO u cfl to u a cfl rH ft a 0 r* rH cO 4J •H C3 M

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208 rH to 4-1 O w a • O 1 J •rH re tfl oc 1 H o 4J rM rt M •H aj rH 0> H a. oo • <4-l
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209 T— t CO 4-1 o CD to o z • Z • • C o o 1 — 1 4-1 H cd CO u B o OO u 0 CD 4J c c H CO CO i— 1 iJ (X H o 00 c 0) • • • • CM iH O o o H o O T3 t£ 3 fH 0) • *H >^ 4-1 •H w H CD CNI co o •H 4-1 CO o XI 4-1 CO • • CO cfl 4-1 o o 1 — I X) e CO o (-1 Q, 13 14-1 o U o c m o H 4-1 •r-t o 01 CO • • > CD W o 1 — 1 OJ 4J o H c 01 u*l •H O o • •H o 14-1 14-1 4J 01 0) c X. O 01 4-1 p M 4-1 o 4-1 c • CO CO o ci 0) •H w 4-1 4-1 C H c CO o CO <-{ *H z CJ 0) 4-1 •r-1 w cO 14-1 w o •H O O c O — 1 oo •H 4-1 U CD c c iH 0) cd CO 4-1 1 6 4J o CO i — 1 4J CX CO z 1 CO O) CO 0) c CJ c II .-1 x: m •H H rH •1-1 XI H CO cd O cO CO CO oo u u i-i z H O

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210 u o 4-1 s u — •v c ~ tn 11 sco • •H — (-1 c > o H u -j H CD S O c O c — Q S-. -J oo j £ 3 o J=Qfi M 03 0 4J 03 c 11 G •H •H O ~ •H <4-l 00 14-1 a) 0 o a c o 0 •H H u 4J c td H -J £ M 3 u 0 0 co c 01 E Z J cfl a) — o c CO c c CU *H cj co a) co PL. C 4J O C -H CO -u i-l CO PL i-H a Q) 6 r— I 3 O U .C O 5 c0 co CO CNI O a CO Z c O o c o o o C •H •U O C3 03 -J C -H 4J c co >-> 60 c CU r-\ CO e i — i u 3 a a) 6 CJ "J i-H 3 CJ M-i u o o u o H JH o CD 5 co ex, Z

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211 OJ co B cj — i H C a e z ^ to a) H U) U-l -j — O C tO =S= — a Cu to w 0) -i CO • H CNI c > o c a •H 0) rl 'J o (0 •H u Jj s O H o co CD i •H M i — 1 3 tH 00 O o 14-1 x: u a M-l 3 c O J c C o o H —i u _j to to H H 0) S 3 o 0 U 0> c-o O O 3 CO o o o o o o o d 4-1 o d -h CO -U rH CO O, t-H d cu 6 — i 3 O CJ X. CJ 13 CO a •rl CO M 60 4-1 CO 0J u U G tO a. o G "J e n) 0J M H 4-> •H tO o CJ > 3J o 0) G c0 U G 60 O is

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212 4_J c GJ ,— 1 o E CO o ; CO o i-H o c c [ — o •H *H 01 *H o ^H O 4-J o to •rH •H (TJ r4 M o — i j: G o 0) 00 (0 O O Oi ,o C r" 1 o o u a. CO c\3 ItH o O rC M-l CO c QJ 4-1 o > co o (3 •H QJ to 4-1 rH rj rH to o a. Q LO *H *H 3 o O tfl qj B — J *H 1M H 3 o *4-< CO 0 O o QJ
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213

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214 3> CO 2 CO Z to z CO z co z CO z z CO Z z w z o o > co z co z CO z en z CO z CO z co z CO z CO z CO z o o CO z CO z CO Z CO Z CO z CO z CO z co z CO Z o CO z CO z co z CO z CO z O a 3 U co z CO z CCD CO z CO z CO z 00 — 1 o m CO CO c z z o o o o CO CO CO CO o z Z z z 1 — o CO co o z Z o H o CO o z cd co z CO z co z o o CO' z o o o P-1 CO z o o 3 3 u CU 3 U a o > 32 H

PAGE 222

215 :H 3 U 0) u cc o CO Z CO Z cr. Z CO Z w Z 00 z CO Z w CO X CO a> CO Z Q 1 Q 1 Q 1 Q i o i PI 3>
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216

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217 H H O > S c oiH CTv m c CO m CO CO co

PAGE 225

218

PAGE 226

219 H pi H O > 3 00 X CN r> CO X \D 00 3 O o O C O ~ o a m 00 c o> r- X v£> O 00 X oo o X o c 3 o o O o O c o H rH 00 00 r C m lO 30 o o o O o O c o 3 1— 1 3 o> 00 X o oo H H

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220 H cd H a > LSI 3 p — C-J c o CNl r CO j ,; — J o o o o o O o o cr O rH cr> n oa \0 ON CO CT> CN oa rH OA rH LO o o O c o o O o o o o o rH LO o> t — cr o> oo CO a* CM 0"> t — 1 o> co o o o C O o o o o o CD —1 n X o CM o> O o O o o o c o o o H H r-> GO CM OA CM CO o o o rH o co o o rH o o r*4 o CJj m to 3 U a N 2 O o > H H

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221 06 c c N 3 C_> c IT) -T co in m in CM in r-. o m m C o O o o o c o o o m OA cn o> o> in CO CO kO co CM 00 o o o o o O o o o o o 1 — 1 l/"l 00 co in o> ^jo o o O o O o O o o H — 1 o\ CC cr> o OA r^< o> r~L-H c^ o o o o O o o o o < — 1 o 00 vO CI OA CO r~o o o O o o O O H o o a U CM co o CO o co r~ o o O o o O 00 OA CO o o O O a 1 — 1 o o> OA o CO CO CC c c o o 1 — I o oa o 'CO a\ o o O H o o ON C a o id o CO CJ 3 O H CrJ H

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222 H H o > o 3 c QJ U o ON H ON 30 c ON o on CO co 3 3 3 3 3 3 o o 3 3 i — ON 00 in H ON m co 1 — 1 00 co CO CO O 3 o o 3 3 3 3 3 i — 1 3 ON CO 3 DC 00 30 CO 3 3 3 3 3 3 3 H ON CO 3 vO CN CO CO r--. CO 3 3 3 3 3 3 3 H ON 00 3 3 ON 3 3 3 3 3 i — i CO co 3 3 3 3 — O 3 3 3 H 3 3 CM 60 S QJ fa 3 2 o o > H tti

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223 H pt! H g O > rH H co o co CC 1^ CO nO r-. lO r— o z G O o O O o o o O 1 — 1 o> CN CN O cn NO as co O on on ON ON 00 cc 00 CN o o O o o o O o o o o i — i o c tSJ 3 u 1 — i CC o ON ON CN o> ON m ON cc vC CC CN 00 o o O o o C a c o o o — H H

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224 H C N 3 u 00 H <* a> 00 CM ON 3 3 3 o O c o C O H X i — 1 CO n oo c o> 1 — 3> r3 3 O O o o C a — 00 o O) CO m 00 CO co n CO o o o O o o o o rH m o CC' •a co n 'CO O c o o O o O — a; *c r cc 00 co o o O o o O 1 — 1 0.62
PAGE 232

APPENDIX C YIELD AND CHEMICAL COMPOSITION OF BAH I AGRA SS AS INFLUENCED BY NITROGEN RATE, SOURCE, AND APPLICATION METHOD

PAGE 233

m a c c cfl N *> CD CD CJ U 3 3 O O CO M co o> c u CO l-i c 0) oo o >J 4_) •H c _op 2£ oo c H i-i CO cfl a u e o CJ CO CO CO C t4 CO O U -H OO -u CO CO •H O XI O &< CO i— ( X QJ OO OJ c n •H J2 3 4-> o i — 1 4-1 01 rH Cfl CJ 0 U UH CD 3 O CO O C/3 j- x: i— 1 4-1 z 3 0) co £ a) u c o 4-1 *H CO 4-1 0) Cfl 4-1 CJ 4-1 •H a. rH rH 01 •H P, Q o a CO cfl rH 1 o 0) 01 4J rH Cfl XI cfl H 00 oo 6 vf N CM n in CM rH CM N CMOCnr^t— I rH ON O CTi O vO v£> vO O vOOvOvO^O *X> vO m u~> O O m vD m O omi m o rH r-~ o vo m in m m m cn cm cm cn cn cm cn cn cn rHcnm^r n h n h h -h cn m m \o r-^ O vo co r~oo O cn m cn co co cm cm c^i c^i a\ h rH h h o\ oi h n o> on cn rH c~oi co m n cm m h m cnvo IM CM N cn CM CM N CM CM CM i — 1 i — I i — I i — I i — I i — I — I CM i — I i — I o co cn 4 rcn cm 4 mo h o is un o on CO CN CO cn cn -J CM CM CM n CNrHrHrHcn CM i — I I — I r — I rH B o m 35 2 o CM I cn o 2 PC cn Z o
PAGE 234

227 H o CN) OS C CN as o rH H O H — CN 00 os c o MO mo MO LO MO MO m SJO MO r-~ a-LO OS CO CM LO rH a> os c r~o < — i o CN a> — CO co ro rH CO CN CN CN CO H CN — — OJ H rH rH i — 1 rH H i — 1 MD rn H m U3 CO' CC H i — i CO CO H CO — ~r H H H CM rH i-i CN i — ( I — 1 H rH CN CN CN H H rH H — 1 r-l rH rH — rH o -dC as as o as u3 00 CN CO CN m CO CO CO m rH m rH OS r> CO CTi O CM CN CN CN c-J CN CN CN CJ OJ i — i — ^CO o> r~ CM r-l CO H O i — i as CO c O LO sO M0 CO 00 r-. CN co m CC r- CO' r-. m o o oo CN rH r- 1 — vO rH CS rH CN H H H rH i — ( rH rH H H m H LO LO m m un os — i — i CS CN CN C-J CN CN cm CN CN rH H rH i — i — co vD o r-j CN rH OJ m rCM lO M3 m LO LO ro CM CN CN CM CN CM CM CM H H rH rH rH i — i — 1 1 H
PAGE 235

228 CM H O H H O O O rH 0> N fO M H N rH O H i — I rH O vD \D ^ >fl ^ \D vC ^ \D iO v£> vO sD vO vO n CO Ol H CO vD00OLOr~ r-~. CM O O st OH H !S o\ m co o r-^ go r-r-. r-~O on CO CO CM M CM CM N n CM CM i — I r— — I i — I rH i — I i — I i — t Ovl i — I ONOr-ir^t— i m oi ci h t*i m o m a\ co m rH a\ r> Ol lO CJ\ >i) <} iClvO -J vO CM O O rI O O O I O •z Z •H _J (0 'J 0 J oor^or^o M rH i — I CM O CM CO nT LO rH v£> CM i — I i — I CM O vO CM CO st l/l rl vD CM H H CM v£> CM in — ) 00
PAGE 236

229 Table C-2. Bahiagrass dry matter yield as affected by rate of nitrogen at three locations. Harvest date Nitrogen rate kg ha kg ha Location 1 0 56 112 168 224 LSD .05 480 1220 1560 1300 1010 510 530 1280 1530 1280 1360 370 810 2060 2270 2250 2240 530 410 810 890 760 870 174 250 220 320 360 330 X NS" Location 2 0 56 112 168 224 LSD .05 720 1380 1190 1370 1410 330 610 1050 1180 1460 1400 210 670 1660 2190 2750 3190 450 420 730 660 830 900 180 Location 3 0 56 112 168 224 490 820 750 740 850 510 890 950 1150 1470 420 750 840 1040 1300 390 600 650 880 1100 280 330 300 420 520 LSD .05 230 270 300 220 130 NS = Not significant at the 0.05 level of probability.

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230 T> o -J u td to n) rJ O •H 4J cd >-i u C cu •J c o (J c cu •H u 3 c tfl to CO :00 td — i ~ td x> u • o c C 4-1 QJ H •H (3 •H CM u-t o •4-1 01 cu cu u U a u I u td H J M 3 0 to -J (3 td .C O

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232 Beaty, E. R. R. A. McCreery, and J. D. Powell. 1960. Response of 'Pensacola' bahiagrass to N fertilization. Agron. J. 52:435-455. Beaty, E. R. J. D. Powell, R. H. Brown, and W. J. Ethredge. 1963. Effect of N rate and clipping frequency on yield of 'Pensacola' bahiagrass. Agron. J. 53:3-4. Beaty, E. R. K. H. Tan, R. A. McCreery, J. H. Edwards, Jr., and R. L. Stanley. 1976. Returned clippings of N fertilization on bahiagrass herbage production and nitrogen and organic matter contents of soil. Agron. J. 68:384-387. Beaty, E. R. K. H. Tan, R. A. McCreery, and John D. Powell. 1980. Yield and N content of closely clipped bahiagrass as affected by N treatments. Agron. J. 72:52-60. Bennett, J. M. 1984. Effects of water stress during vegetative growth on corn grain yields. Agronomy Facts No. 162, Florida Cooperative Extension Service, University of Florida, Gainesville, Florida. Bennett, 0. L., E. L. Mathias, and C. B. Sperow. 1976. Double cropping for hay and no-tillage corn production as affected by sod species with rates of atrazine and nitrogen. Agron. J. 68:250254. Bennett, W. F. 1971. A comparison of the chemical composition of the corn leaf and the grain sorghum leaf. Comm. Soil Sci. Plant Anal. 2:399-405. Bennett, W. F. G. Stanford, and L. Dumenil. 1973. Nitrogen, phosphorus, and potassium content of the corn leaf and grain as related to nitrogen fertilization and yield. Soil Sci. Soc. Proc. 17:252-258. Benoit, G. R. A. L. Hatfield, and J. L. Ragland. 1965. The growth and yield of corn. III. Soil moisture and temperature effects. Agron. J. 57:223-226. Blevins, R. L. D. Cook, S. H. Phillips, and R. E. Phillips. 1971. Influence of no-tillage on soil moisture. Agron. J. 63:593-596. Blue, W. G. 1966. The effect of nitrogen sources, rates, and application frequencies on 'Pensacola' bahiagrass forage yields and nitrogen utilization. Soil Crop Sci. Soc. Fla. Proc. 26:105-109. Blue, W. G. 1972. The role of 'Pensacola' bahiagrass ( Paspalum notatum Flugge) stolon-root systems in fertilizer nitrogen utilization on Leon fine sand. Agron. J. 65:88-91. Blue, W. G. 1974. Efficiency of five nitrogen sources for 'Pensacola' bahiagrass on Leon fine sand as affected by lime treatments. Soil Crop Sci. Soc. Fla. Proc. 33:171-180.

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235 Eylands, V. J. 1984. Corn and grain sorghum yield and mineral nutrition in multicropping systems. Ph.D. dissertation, University of Florida, Gainesville, Florida. Fenn, L. B. and D. E. Kissel. 1976. The influence of cation exchange capacity and depth of incorporation on ammonia volatilization from ammonium compounds applied to calcareous soils. Soil. Sci. Soc. Am. J. 40:394-397. Fink, R. J., and Dean Wesley. 1974. Corn yield as affected by fertilization and tillage system. Agron. J. 66:70-71. Ford, C. W., and W. T. Williams. 1973. In vitro digestibility and carbohydrate composition of Digitaria decumbens and Setaria anceps grown at different levels of nitrogenous fertilizer. Aust. J. Agric. Res. 24:309-316. Follett, R. F., and S. R. Wilkinson. 1985. Soil fertility and fertilization of forages. p. 309. In M. E. Heath, R. F. Barnes, D. S. Metcalfe (eds.), Forages: The Science of Grassland Agriculture, 4th edition, Iowa State University Press, Ames, Iowa. Fox, R. H. and L. D. Hoffman. 1981. The effect of N fertilizer source on grain yield, N uptake, soil pH, and lime requirements in no-till corn. Agron. J. 73:891-895. Fribourg, H. A. 1974. Fertilization of summer annual grasses and silage crops, pp. 189-212. In D. A. Mays (ed.), Forage Fertilization, Am. Soc. of Agron., Madison, Wisconsin. Fribourg, H. A., W. E. Bryan, G. M. Lessman, and D. M. Manning. 1976. Nutrient uptake by corn and grain sorghum silage as affected by soil type, planting date, and moisture regime. Agron. J. 68:260263. Fribourg, H. A., N. C. Edwards, Jr., and K. M. Barth. 1971. In vitro dry matter digestibility of 'Midland' bermudagrass grown at several levels of N fertilization. Agron. J. 63:786-788. Gallaher, R. N. 1977. Soil moisture conservation and yield of crops no-till planted in rye. Soil Sci. Soc. Am. J. 41:145-147. Gallaher, R. N. 1978. Multiple cropping-value of mulch. Proceedings of the First Annual Southeastern No-Till Systems Conference, Agronomy Department, Georgia Experiment Stations, Experiment, Georgia, pp. 9-13. Gallaher, R. N. 1980. Potential and projection for increasing agronomic production with multiple cropping and/or minimum tillage systems in Florida. Fla. Coop. Ext. Ser. Cir. 479, University of Florida, Gainesville, Florida.

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243 Smith, Floyd W. 1966. Application of ammonia. In H. McVicker, W. P. Martin, Ivan E. Miles, and H. A. Tucker (eds.), Agricultural Anhydrous Ammonia Technology and Use. Agr. Ammonia Inst., Memphis, Tennessee. Stanley, R. L. E. R. Beaty, and J. D. Powell. 1977. Forage yield and percent cell wall constituents of 'Pensacola' bahiagrass as related to N fertilization and clipping height. Agron. J. 69:501-504. Stanley, R. L. Jr., and R. N. Gallaher. 1980. No-tillage versus conventional corn in bahiagrass sod with soybeans following, pp. 151-155. In R. N. Gallaher (ed.), Proceedings of the Third Annual No-TillageH5ystems Conference, Agronomy Department, University of Florida, Gainesville, Florida. Terman, G. L. 1979. Volatilization of nitrogen as ammonia from surface applied fertilizers, organic amendments and crop residues. Adv. Agron. 31:189-223. Tesar, M. B. 1969. Grasses with nitrogen vs. legume grass mixtures in northern Michigan. Michigan Agr. Exp. Sta. Res. Rep. 90:44-46. Tesar, M. B. 1974. Use of anhydrous ammonia and fluid fertilizers on grass. pp. 539-543. In D. A. Mays (ed.), Forage Fertilization, Am. Soc. Agron., Madison, Wisconsin. Tesar, M. B., C. M. Hansen, and L. S. Robertson. 1972. Increasing grass yield with anhydrous ammonia (Progress Report) Michigan Agr. Exp. Sta. Res. Rep. 166:99-104. Thomas, G. W. R. L. Blevins, R. E. Phillips, and M. A. McMahon. 1973. Effect of a killed sod mulch on nitrate movement and corn yield. Agron. J. 65:736-739. Tilley, J. M. A., and R. A. Terry. 1963. A two-step technique for the in vitro digestion of forage crops. J. Br. Grassl. Soc. 18: 104-111. Touchton, J. T. 1980. Soil fertility and its relationship to crop production cost in no-tillage systems, pp. 180-187. In R. N. Gallaher (ed.), Proceedings of the Third Annual No-Tillage System Conference, Agronomy Department, University of Florida, Gainesville, Florida. Touchton, J. T., and W. L. Hargrove. 1982. Nitrogen sources and methods of application for no-tillage corn production. Agron. J. 74:823-826. Tucker, Billy B. and G. B. Crowe. 1966. The profitability of anhydrous ammonia use as a fertilizer. _In Malcom H. McVicker, W. P. Martin, Ivan E. Miles, and H. A. Tucker (eds.), Agricultural Anhydrous Ammonia Technology and Use. Agr. Ammonia Inst., Memphis, Tennessee.

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244 Tyner, E. H. 1946. The relation of corn yields to leaf nitrogen, phosphorus, and potassium fertilization of non-tilled maize. Agron. J. 61:637-639. Ulrich, A. 1952. Physiological bases for assessing the nutritional requirements of plants. Am. Rev. of Plant Physiol. 3:207-228. Unger, P. W. 1978. Straw mulch effects on soil temperatures and sorghum germination and growth. Agron. J. 70:858-864. Valentine, J. H. and A. B. Onker. 1968. Fertilizer research and demonstration summary for the Texas High Plains, 1958-1967. Texas Agric. Exp. Stn. MP217, College Station, Texas. Van Soest, P. J. 1982. Nutritional Ecology of Ruminants. 0 and B Books, Corvallis, Oregon. Van Soest, P. J. 1985. Composition, fiber quality, and nutritive value of forages. pp. 418-420. In M. E. Heath, R. F. Barnes, D. S. Metcalfe (eds.), Forages: The Science of Grassland Agricul ture, 4th edition, Iowa State University Press, Ames, Iowa. Vanderlip, R. L. and H. E. Reeves. 1972. Growth stages of sorghum. Agron. J. 64:13-16. Volk, G. M. 1959. Volatile loss of ammonia following surface applica tion of urea to turf or bare soil. Agron. J. 51:746-749. Waite, R. 1970. The structural carbohydrates and the in vitro digestibility of a ryegrass and a cocksfoot at two levels of nitrogenous fertilizer. J. Agr. Sci. 74:457-462. Warren, H. L. D. M. Huber, C. Y. Tsai, and D. W. Nelson. 1980. Effect of nitrapyrin and N fertilizer on yield and mineral composition of corn. Agron. J. 72:729-732. Watson, D. J. 1958. The dependence of net assimilation rate on leaf area index. Ann. Bot. 22:37-54. Webster, J. E., J. W. Hogan, and W. C. Elder. 1965. Effect of rate of ammonium nitrate fertilization and time of cutting upon selected chemical components and the in vitro rumen digestion of bermudagrass forage. Agron. J. 57:323-325. Widstrom, N. W. and J. R. Young. 1980. Double cropping corn on the Coastal Plain of the southeastern United States. Agron. J. 72: 302-305. Wilkinson, S. R. and G. W. Langdale. 1974. Fertility needs of warm season grasses. pp. 119-141. In D. A. Mays (ed.), Forage Fertilization, Am. Soc. of Agron., Madison, Wisconsin.

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245 Wilson, J. R. 1973. Influence of aerial environment, nitrogen supply, and ontogenetical changes on the chemical composition and digestibility of Panicum maximum var. 1 trichoglume Aust. J. Agric. Res 24:543-546. Wilson, J. R., and C. W. Ford. 1973. Temperature influences on in vitro digestibility and soluble carbohydrate accumulation of tropical and temperate grasses. Aust. J. Agric. Res. 24:178-198. Wilson, J. R., and K. P. Haydock. 1971. The comparative response of tropical and temperate grasses to varying levels of nitrogen and phosphorus nutrition. Aust. J. Agric. Res. 22:573-587. Wilson, J. R. and D. J. Minson. 1980. Prospects of improving the digestibility and intake of tropical grasses. Trop. Grasslands 14:253-259. Wilson, J. R., A. 0. Taylor, and G. R. Dolby. 1976. Temperature and atmospheric humidity effects on cell wall content and dry matter digestibility of some tropical and temperate grasses. N.Z. J. Agric. Res. 19:41-46. Yamaguchi, J. 1974. Varietal traits limiting the grain yield of tropical maize. Soil Sci. Plant Nutr. 20:69-78. Young, J. R., H. R. Gross, Jr., W. K. Martin, and W. C. McCormick. 1978. Double cropping field corn in south Georgia with an insect and disease control program. Univ. of Georgia Res. Bull. 227, Athens, Georgia, pp. 1-11.

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BIOGRAPHICAL SKETCH John A. Baldwin was born on 11 May 1947 in Zanesville, Ohio. He received his B.S. degree from Colorado State University in 1969 and his M.S. degree from the University of Florida in 1973. He served as a County Extension Agent in Madison, Florida, from 1973 to 1975. In 1975, he accepted the position of County Extension Director in Levy County, Florida, and continues in that position as he pursues the Ph.D. degree in agronomy from the University of Florida. He, his wife, Marilyn, and sons, Matt and Jason, have lived in Bronson, Florida, from 1975 until the present. 246

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Raymond N. Gallaher Chairman Professor of Agronomy I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Je#y M.*/Bennett Associate Professor of Agronomy I certify that I have read this study and that in my opinion It conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. VyyvTWy/ J^i (^^XX^/ J immy G.ACheek Brofessor of Agricultural and Extension Education I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. )hn E. Moore 'rofessor of Animal Science

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Associate Professor of Soil Science This dissertation was submitted to the Graduate Faculty of the College of Agriculture and to the Graduate School and was accepted as partial fulfillment of the requirements for the degree of Doctor of Philosophy. December 1985 Dean, Cpllege of Agriculture Dean, Graduate School