Group Title: Research report (North Florida Research and Education Center (Quincy, Fla.))
Title: Differences in corn hybrids to starter placement and rate
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Permanent Link: http://ufdc.ufl.edu/UF00066118/00001
 Material Information
Title: Differences in corn hybrids to starter placement and rate
Series Title: Research report (North Florida Research and Education Center (Quincy, Fla.))
Physical Description: 15 p. : ; 28 cm.
Language: English
Creator: Rhoads, Fred ( Frederick Milton )
Teare, I. D ( Iwan Dale ), 1931-
Wright, D. L ( David L )
North Florida Research and Education Center (Quincy, Fla.)
Publisher: North Florida Research and Education Center
Place of Publication: Quincy Fla
Publication Date: 1994
 Subjects
Subject: Corn -- Florida   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p.12-13).
Statement of Responsibility: F.M. Rhoads, I.D. Teare and D.L. Wright.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00066118
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 71174107

Full Text

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DIFFERENCES IN CORN HYBRIDS TO STARTER PLACEMENT AND RATE



F. M. Rhoads, I.D. Teare*

and

D.L. Wright


All authors, Univ. of Florida, NFREC, Rt. 3 Box 4370, Quincy, FL
32351. Florida Agric. Exp. Stn. Rep. No. NF 94-2. *Corresponding
author.









ABSTRACT

Corn (Zea mays L.) hybrids differ in response to starter

fertilizer, but the cause is not known Two glasshouse

experiments were conducted to characterize a responsive and a non-

responsive corn hybrid in relation to root growth, P and N uptake,

and nutrient uptake efficiency. Applied phosphorus levels of 0,

10, 20, or 30 mg kg- were mixed with the total soil volume (1.5 L)

in pots in experiment I. Nitrogen was applied at a constant rate

(100 mg pot-') and also mixed with the total volume of soil.

Phosphorous rates were 0, 30, or 60 mg kgI' in experiment II.

Varying P levels and one level of N (200mg pot-') were mixed with

total soil volume (BC) or banded (BD) 5 cm vertically below the

soil surface and 5 cm horizontally from the seed planted 2.5 cm

deep. The soil was obtained from the A horizon of Norfolk loamy

fine sand (fine loamy, siliceous, thermic, Typic Kandiudult) with

low available P and high P fixing capacity. Root weight was 31%

and 48% greater for the non-responsive hybrid (NK 508) than the

responsive hybrid (G4733) for experiment I and II, respectively.

This indicates that the non-responsive hybrid was able to tap a

larger N and P supply than the responsive hybrid in low P soil with

high fixation capacity. The responsive hybrid produced a

significant (P = 0.05) increase in root weight due to banding N

only, but the non-responsive hybrid did not respond to N placement.

The conclusion was that hybrid response to starter fertilizer was

a function of differences in root growth.








Environmental factors that influence response to starter

fertilizer are soil temperature, phosphorus (P) immobilization, and

low fertility soils. Low soil temperatures reduce root growth

(Mackay and Barber, 1984) which in turn reduces nutrient uptake of

plants with limited root systems. Early planting dates, to

maximize corn yield potential (Wright et al., 1988) often result in

exposure of young seedlings to low soil temperatures. Starter

fertilizer increased corn yield in every case when either air or

soil temperature was below normal in a Canadian study (Ketcheson,

1968). Poor seedling growth resulting from low nutrient

availability of N and P in cold soils can occur irrespective of

residual soil fertility levels (Touchton and Hargrove, 1983). Both

N and P are considered essential ingredients in starter fertilizers

* (Ketcheson, 1957) to offset low N and P availability in cold soils

(Cassman and Munns, 1980; and Wallingford, 1978).

Some soils have a high capacity to fix or immobilize

fertilizer P, thereby reducing its availability to plants with

limited root systems. Research has shown that there is an optimum

fraction of soil with which to mix a given amount of fertilizer P

in order to obtain maximum P uptake in a given soil (Anghinoni and

Barber, 1980). Where one rate of P was applied to three soils, the

greater the adsorption of P by the soil, the lower the fraction of

P-treated soil necessary to maximize P-uptake. Response to starter

fertilizer in soils with high P adsorption (as in the Southeast)

will be due to added P. Low fertility soils provide a more

favorable environment for plant response to starter fertilizer than









high fertility soils. Placing starter fertilizer in a band near

the seed in a low fertility soil .gives a dramatic increase of

nutrient concentration in the limited root zone of young seedlings

and promotes more rapid growth.

Corn hybrids have been shown to respond differently in grain

yield to starter fertilizer (a small amount of N and P fertilizer

band applied near the seed at planting) in a 3 yr field experiment

at Quincy, Florida (Teare and Wright, 1990). Some were consistent

positive responders, some were not responders and some were

inconsistent. Hybrid characteristics that influence grain yield

response to starter fertilizer include rate of root growth, P-

uptake efficiency, N-uptake efficiency, rate of top growth, and

growth response to temperature. Hybrids that are highly sensitive

to temperature are expected to be inconsistent in response to

starter fertilizers because when temperature is higher than normal

a positive response is not likely to occur while below normal

temperatures would probably result in a positive response. A

hybrid having a high rate of root growth that produces a large root

system, and a high efficiency of N and P uptake is considered to

have root adequacy under suboptimal conditions (i.e., cold or high

P fixing soils) and is not expected to have a positive response to

starter fertilizer. A hybrid having a slow rate of root growth,

resulting in a small root system, and/or low nutrient uptake

efficiency does not have a root adequacy under suboptimal

conditions and a positive response to starter fertilizer is

expected.









Two experiments were conducted to compare the root growth and

* N and P uptake efficiency of pre-selected responsive and non-

responsive corn hybrids to starter fertilizer application. Our

hypothesis was that a corn hybrid not positively responsive to

starter fertilizer has a more rapid rate of root growth and/or a

higher N and P uptake efficiency than a corn hybrid that

consistently responded positively. The objective of experiment I

was to measure the differences between hybrids in root growth with

varying phosphorous rates at a constant N and K rate on responsive

and non-responsive corn hybrids. The objectives of experiment II

were to measure the differences between hybrids in root growth,

total nutrient uptake and efficiency of P and N uptake from

broadcast (BC) and banded (BD) fertilizer (band placement was used

S to simulate starter fertilizer) applications to define root

adequacy.









METHODS AND MATERIALS

'Deltapine G4733' and 'Northrup King 508'(hereafter referred to

as G4733 and NK 508, respectively) were selected because G4733

consistently gave a positive grain yield response to starter

fertilizer and NK 508 consistently gave no response to starter

fertilizer in a 3 year field study at Quincy, Florida (Teare and

Wright, 1990) leading to the premise that G4733 was root adequate

and NK 508 was not root adequate. The corn hybrids were seeded in

pots (15 cm wide by 12 cm deep) containing 2 kg of soil. The

potting soil was taken from the A horizon of Norfolk loamy fine

sand (fine loamy, siliceous, thermic, Typic Kandiudult) low in

available P because of a high fixation capacity. Seed for

experiment I and II were planted on 15 August 1991 and 17 March

1992 in two glasshouse studies at Quincy, Florida. Average minimum

and maximum temperatures were 21' and 32' C, respectively, in

experiment I and 11' and 24 C in experiment II. Six seeds were

planted 2.5 cm deep at the center of each pot. Plants were thinned

to two per pot at the two-leaf stage. Both experiments were limed

by mixing 2000 mg CaO pot-' uniformly with 2 kg of soil. Soil pH

was determined with a pH meter in a 1:1 v/v soil:water slurry for

each experiment. Soil for the first experiment averaged pH 6.1

with a range of + 0.7 and a standard deviation of 0.2. For the

second experiment, soil average was pH 6.7 with a range of + 1.2

and a standard deviation of 0.3.

The P rates for experiment I were 0, 10, 20, and 30 mg kg"'

(Table 1) (1mg kg-1 is approximately equal to 2 kg ha'-) (triple super








phosphate). Placement of P was mixed with total soil volume in the

pot to simulate broadcast application (BC). The N (100 mg N pot-'

[mg pot-' is approximately equal to kg ha-1]) and K (281 mg K pot-')

were kept constant and applied as potassium nitrate (KNO3).

Since some P deficiency was observed in experiment I, the

highest P rate was doubled in experiment II and P rates changed to

0, 30, and 60 mg kg'. Nitrogen and K rates were increased

correspondingly to 200 mg pot-' as NH4NO3and 415 mg K pot-' as K2SO4.

Phosphorus and N were applied broadcast (mixed with total soil

volume) or banded across the center of the pot in a V cut to 5 cm

below the surface and 2.5 cm wide at the top. Seed was planted at

2.5 cm depth and 2.5 cm from the edge of both sides of the top of

the V or 5 cm horizontally from the center of the V. The single

* rate of N was broadcast, banded with the P, or banded alone with

broadcast P at the 60 mg kg-' rate (Table 2).

Plants were harvested 33 days after seeding for experiment I

and 41 days after seeding for experiment II. Roots were separated

from the soil by washing the soil through a screen with tap water.

Root dry-matter yield was determined after drying to constant

weight at 70C. Top dry-matter data was collected but not reported.

Tissue P was determined separately for roots and tops on a

colorimeter by the molybdenum-blue method after ashing plant

samples at 5000C. These values were multiplied by the grams of root

and top dry-matter to determine total P uptake of roots and tops.

Tissue N was determined by micro-kjeldahl procedures and total N

uptake was calculated in the same manner as was P. Soil-test P









(sampled at harvest) was determined in a Mehlich-1 extract (Hanlon

and Devore, 1989), using the molybdenum-blue method. In general,

Mehlich-1 extractable soil P at harvest was increased about 7 or 8

mg kg-' by each 30 mg kg-' fertilizer P in experiment II.

The experimental design for each experiment was a randomized

complete block containing four replicates. Statistical analysis

consisted of analysis of variance, regression analysis, and single

degree-of-freedom contrasts (Steel and Torrie, 1960).








RESULTS AND DISCUSSION
Root growth, total P uptake (root and top), and P uptake

efficiency (P uptake/g roots) were measured in experiment I for two

hybrids that reacted differently to starter fertilizer application

in a previous field experiment (Teare et al., 1990). Deltapine

G4733 grain yield had consistently responded positively to starter

fertilizer (RH) and Northrup King NK 508 had consistently given no

response to starter fertilizer (NRH). Mean root dry matter (a

measure of root growth) was 28% greater in NK 508 (NRH) than in

G4733 (RH) in experiment I (Table 1). Total P uptake of roots and

tops of the two hybrids increased linearly in relation to the

amount of P applied and the total P uptake of the NRH was 29%

greater than the RH. Phosphorous uptake efficiency (mg P/g roots)

* was not significantly different between hybrids. Since there was no

significant difference between hybrids in P uptake efficiency the

increased P uptake by the NRH was due to increased root growth,

which indicated that root growth of the NRH was sufficient to

obtain P for maximum yield without starter fertilizer.

Band placement (to simulate starter fertilizer) of P (varying

amounts) and N (a constant amount) was added to experiment II for

comparison with broadcast fertilizer application to define root

adequacy. The hypothesis was that band placement would increase

root growth by minimizing P and soil contact to a much greater

extent than broadcast application (mixing the N and P in the total

soil volume). All hybrids should respond to banding in low P soils

with high fixation capacity, but the hypothesis was that a small









root system would respond to banding more in proportion to size

than a large root system which would exploit a larger soil volume

and obtain more available P.

Dry-matter yield of roots of both hybrids was increased by

band placement at each P fertilizer rate in experiment II (Table

2). Band placement of N and P at 30 mg P kg-' compared to broadcast

increased root growth of the RH by 103 % (3.19 vs. 157 g pot-1) and

of the NRH by 80% (4.68 vs. 2.60 g pot-). The difference between

hybrids was even greater at 60 mg P kg1 with band placement

producing 1345 (4.75 vs. 2.03 g pot-1) more root weight than

broadcast for the RH but only 72% (6.56 vs. 3.81 g pot-1 more for

the NRH. This supports the hypothesis that a slower growing

(smaller) root system responds to starter fertilizer more in

proportion to size than a larger (faster) growing root system .

Root growth was 48% greater for the NRH than RH, averaged

overfertilizer treatments. Total P uptake was 25% greater and

total N uptake was 16% greater for NRH than RH. However, P uptake

efficiency was 17% greater and N uptake efficiency was 30% greater

for RH than NRH. Increased uptake efficiencies were not great

enough to offset the difference in root growth.

Band placement of N was compared to broadcast N root growth

dry-matter yield of the RH was increased 76% (3.58 vs. 2.03 g pot-1)

but the increase of the banded over-the broadcast N (4.45 vs. 3.81

g pot-) fpr NRH was only 17% and was not significant (P > 0.05).

The total N uptake of the NRH was influenced more by P rate (137

vs. 175 mg) than by N placement (175 vs. 177 mg). The opposite was








true for the RH which showed a 20 mg (104 vs. 124 mg) increase due

to P rate and a 57 mg (181 vs. 124 mg)increase due to N placement.

Nitrogen uptake was increased 46% (181 vs. 124 mg) in the RH by

band applied N, but only 1% in the NRH (177 vs. 175).

Both experiments are in agreement that the NRH had the largest

root system in terms of dry-matter yield and also took up the most

P in a starter fertilizer system. The RH was most efficient in

taking up N and P per g of roots but this was more than offset by

the enhanced root system of the NRH. We conclude that the

difference in response between the two hybrids to starter

fertilizer was due to a difference in growth of root systems.

As previously stated, only one of these hybrids responded to

band placement (starter fertilizer) of N and P in the field

* experiment where Mehlich-1 P was high (>31 mg kg'1). However, both

hybrids responded to band placement of P and N in the low P soil of

the pot experiments. Since only the hybrid that responded to N and

P in the field responded to N placement in the potexperiments, this

suggests that the positive response of some hybrids to starter

fertilizer in the field may be due to N placement. The difference

between these hybrids in response to N placement may explain why

conflicting results have been obtained with starter fertilizers

containing N and P (Teare and Wright, 1990).









REFERENCES

Anghinoni, I., and S.A. Barber. 1980. Predicting the most

efficient phosphorus placement for corn. Soil Sci. Soc. Am.

J. 44:1016-1020.

Cassman, K.G., and D.N. Munns. 1980. Nitrogen mineralization as

affected by soil moisture, temperature, and depth. Soil Sci

Soc. Am. J. 44:1233-1237.

Hanlon, E.A., and J.M. Devore. 1989. IFAS extension soil testing

laboratory chemical procedures and training manual. Florida

Cooperative Extension Service. Circular 812.

Ketcheson, J.W. 1957. Some effects of soil temperature on

phosphorus requirements of young corn plants in the

greenhouse. J. Soil Sci. 37:41-47.

Ketcheson, J.W. 1968. Effect of controlled air and soil

temperature and starter fertilizer on growth and nutrient

composition of corn (Zea mays L.) Soil Sci. Soc. Amer. Proc.

32:531-534.

MacKay, A.D., and S.A. Barber. 1984. Soil temperature effects on

root growth and phosphorus uptake by corn. Soil Sci. Soc. Am.

J. 48:818-823.

Steel, R.G.D., and J.H. Torrie. 1960. Principles and procedures

of statistics. McGraw-Hill, NY.

Teare, I.D., and D.L. Wright. 1990. Corn hybrid-starter

fertilizer interaction for yield and lodging. Crop Science.

30:1298-1303.








Touchton, J.T., and W.L. Hargrove. 1983. Grain sorghum response

to starter fertilizers. Better Crops Plant Food 67:1-3.

Wallingford, W. 1978. Phosphorus in starter fertilizer. p. 62-79.

In C. P. Ellington (ed.) Phosphorus for agriculture. Potash

& Phosphate Inst., Atlanta, GA.

Wright, D.L., I.D. Teare and B.T. Kidd. 1988. Ontogeny of.maize

in relation to sequential cropping. Trop. Agric. (Trinidad)

65:169-172.









Table 1. Dry matter yield, total P uptake and P uptake per gram of
roots of G4733 and NK 508 two corn hybrids. Single
degree-of-freedom comparisons for effect of hybrid are
shown at the bottom. Experiment I. (33 days after
planting).




Total Nutrient uptake
P treatment Root P uptake efficiency
Rate Placementt Dry-matter (Root & top) (P g1 of roots)


mg kg"'


-----g pot-'----- mg pot-1


mg g-1


Responsive hybrid (G4733)
0 -- 0.95 2.18 2.32
10 BC 1.14 3.14 2.69
20 BC 1.68 3.67 2.23
30 BC 1.85 5.47 3.00

Non-responsive hybrid (NK 508)
0 -- 1.31 3.16 2.41
10 BC 1.68 3.56 2.05
20 BC 1.92 5.19 2.71
30 BC 2.28 6.74 2.99


Isd (0.05)


0.45


1.15


0.87


Orthogonal comparison Roots Total-P mg P g-1 roots


F value
G4733 vs NK508 31.02** 8.42** N.S.


tBC = P mixed with total soil volume, WB = P mixed with 25% of soil
volume. N was mixed with total soil volume in all treatments.

**denotes significance at 1% probability. N.S. = not significant.









Table 2. Dry matter yield, total P and N uptake, P uptake per gram of
roots, and N uptake per gram of roots of G4733 and NK 508.
Single degree-of-freedom comparisons for effect of hybrid are
shown at the bottom. Experiment II. (41 days after planting).


Total Uptake
P treatment Nitrogen Roots (Root & Top)
Rate Placementt placement Dry matter P N


---g pot-'--- --mg pot-'--


Nutrient uptake
efficiency
(g' roots)
P N


mg g'


- ---------------------Responsive hybrid (G4733)-----------------
0 BC 1.15 1.59 54 1.42 4
30 BC BC 1.57 2.77 104 1.82 6
60 BC BC 2.03 4.74 124 2.36 6
60 BC BD 3.58 9.05 181 2.53 5
30 BD BD 3.19 5.63 165 1.81 5
60 BD BD 4.75 11.22 179 2.44 4


Non-responsive hybrid (NK
0 BC 1.91 2.08
30 BC BC 2.60 4.46
60 BC BC 3.81 7.72
60 BC BD 4.45 9.65
30 BD BD 4.68 7.39
60 BD BD 6.56 12.43


508)--------------


81
132
175
177
176
192


1.09
1.74
2.03
2.18
1.60
1.92


Isd (0.05)


0.85


1.64 23


0.47 9.9


Dry-matter Total uptake Uptake mc g-1 roots
Comparison Tops Roots P N P N
F value---------------
G4733 vs NK 508 35.12** 58.09** 19.70** 20.97** 10.28** 37.63**

tBC = N and P mixed with total soil volume, BD = band placement of N and
P was 5 cm below soil surface and 5 cm horizontal from seed.


Selected degrees of freedom, F values, and level of significance from
ANOVA


Source df


Fert.
Hybrid
Fx H


Roots
(wt)


52.0537***
58.0323***
1.2745NS


Total uptake
P ]


82.45***
19.67***
1.309NS


63.37***
20.58***
2.68*


Uptake effic.
P N

12.50*** 11.66***
10.26** 39.28***
0.424 0.55NS


*,**,*** denotes significance at 0.05, 0.01, 0.001 probability.


mg kg'


4P N


. 1 I >






4 r




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