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FLAG IFAS PALMM UF



Annual rice field day
ALL VOLUMES CITATION SEARCH THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00054448/00004
 Material Information
Title: Annual rice field day
Series Title: Belle Glade EREC research report
Physical Description: v. : ill. ; 28 cm.
Language: English
Creator: Belle Glade AREC
Belle Glade EREC (Fla.)
Publisher: University of Florida, Institute of Food and Agricultural Sciences, Cooperative Extension Service, Agricultural Research and Education Center.
Place of Publication: Belle Glade FL
Creation Date: 1987
Frequency: annual
regular
 Subjects
Subjects / Keywords: Rice -- Field experiments -- Periodicals -- Florida   ( lcsh )
Rice -- Diseases and pests -- Periodicals -- Florida   ( lcsh )
Rice -- Periodicals -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
serial   ( sobekcm )
 Notes
Dates or Sequential Designation: Began 1978?
Dates or Sequential Designation: Ceased in 1991 or 1992.
Issuing Body: Prior to 1984 this was issued by the Agricultural Research and Education Center (Belle Glade, Fla.), which changed its name to the Everglades Research and Education Center.
General Note: Description based on: 4th (1981); title from cover.
General Note: Latest issue consulted: 11th (1991).
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 40942624
lccn - 2006229205
System ID: UF00054448:00004
 Related Items

Table of Contents
    Copyright
        Copyright
    Title Page
        Title Page
    Table of Contents
        Table of Contents
    How the rice council is helping the U.S. rice industry ( Mr. Charles Wilson )
        Page 1
        Page 2
    Calcium silicate slag, nitrogen, and manganese fertilization studies - 1986 (Dr. G. H. Snyder and D.B. Jones )
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
    Update on weed control methods in rice culture ( Dr. J. A. Dusky )
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
    DD50 rice management program : theory and use ( Dr. F. J. Coale )
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
    DD50 rice management program: Importance of various predicted growth stages (Dr. D. B. Jones)
        Page 18
        Page 19
        Page 20
        Page 21
    A chronology of rice research, everglades research and education center
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
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        Page 53
        Page 54
        Page 55
Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




/DZII


Belle Glade EREC Research Report EV-1987-2


FOURTH ANNUAL RICE FIELD DAY
July 7. 1981


FIFTH ANNUAL RICE FIELD DAY
July 22 1982


SEVENTH ANNUAL RICE FIELD DAY
July 18, 1984


EIGTH ANNUAL RICE FIELD DAY
July 10, 1985


NINTH ANNUAL RICE FIELD DAY
August 1, 1986


TENTH ANNUAL RICE FIELD DAY

UNIVERSITY OF FLORIDA
EVERGLADES RESEARCH AND DEDICATION CENTER
INSTITUTE OF FOOD AND AGRICULTURAL SCIINCI1S
COOPERATIVE\ EXTENSION SERVICE
BELI F GLADE, FLORIDA
JUI Y 10, 1987


RICE FIELD DAY Progam
August8, 1978


-I







TENTH ANNUAL RICE FIELD DAY


EVERGLADES RESEARCH AND EDUCATION CENTER
BELLE GLADE, FLORIDA


JULY 10, 1987


FRANK J. COALE, PRESIDING
ASSISTANT PROFESSOR, EXTENSION AGRONOMIST


DISCUSSION SESSION


Welcome Remarks/Opening Comments.
Dr. V. H. Waddill, Center Director-EREC


How the Rice Council is Helping the U.S. Rice Industry.
Mr. Charles Wilson, Manager-Membership Programs, Rice
Council For Market Development


Calcium Silicate Slag, Nitrogen, and Manganese
Fertilization Studies 1986
Drs. G. H. Snyder and D. B. Jones


Update on Weed Control Methods in Rice Culture.
Dr. J. A. Dusky


DD0 Rice Management Program: Theory and Use.
Dr50F. J. Cole
Dr. F. J. Coale


DD Rice Management Program:
Predicted Growth Stages.
Dr. D. B. Jones


Importance of Various


Open Discussion of Current Research and Production Problems.
Dr. D. B. Jones


APPENDIX: A Chronology of Rice Research, Everglades Research
and Education Center


Page


8:30



8:40




8:55




9:10



9:25


9:40




9:55






How the Rice Council is Helping the U.S. Rice Industry

Charles Wilson*



THE RICE COUNCIL-

The Rice Council for Market Development is a nonprofit organization

established to promote the consumption of U.S. grown rice in domestic and

foreign markets.

Supported by all segments of the rice industry, the Rice Council unites the

rice growers and millers of Arkansas, California, Louisiana, Mississippi,

Missouri and Texas.

U.S. rice consumption was declining before the Council was formed in 1959.

Since then, this downward trend has been reversed and per capital consumption has

steadily increased.

Through export programs, the United States has been established as one of

the world's largest suppliers of high quality rice.

Current programs continue to grow and will develop according to industry

needs.

DOMESTIC PROGRAMS

Advertising in major magazines reaches homemakers and the foodservice

trade, stressing rice's advantages.

Well trained home economists appear on television programs, radio talk

shows and news broadcasts nationwide.

Rice recipes for restaurants, homes, school lunch programs, cafeterias,

airlines, military, hospitals and nursing homes are developed and distributed

across the country.




*Manager-Membership Programs, Rice Council For Market Development, Houston, TX


Page 1






Publicity programs and press service achieve valuable editorial coverage in

national magazines, weekly and daily newspapers and on radio and television.

Close personal contacts are maintained with media, school, university and

other professionals who can acquaint consumers with rice.

INTERNATIONAL PROGRAMS

Adaptations of Rice Council programs to fit the particular need of various

countries are achieved through a cooperative program with the U.S. Department of

Agriculture's Foreign Agricultural Service and its counselors, attaches, and

agricultural trade officers throughout the world,

Advertising and public relations programs are conducted in Europe, the

Middle East, Africa and other foreign markets.

Potential customers are invited to the U.S. rice growing areas to acquaint

them with high quality U.S. rice, the marketing system and the industry's

reliability.

Market research is conducted and trade relations are developed to improve

existing markets and develop new markets for American rice.

Contact is maintained with the rice trade through international trade

shows, personal associations, and the agricultural attaches/counselors

affiliated with the USDA.

Educational programs are conducted and developed, and materials are created

for rice purchasing agencies of foreign governments and private and commercial

interests.

Barriers to rice sales are reduced and trade opportunities are protected.


Page 2






Calcium Silicate Slag, Nitrogen, and Manganese Fertilization Studies 1986

G. H. Snyder and D. B. Jones*



Calcium silicate slag and nitrogen

In several past field day reports (1982-86) and in other publications

(Snyder et al., 1986; Anderson et al., 1987) it has been demonstrated that rice

production is greatly increased on most organic soils in the Everglades by

pre-plant application of calcium silicate slag to provide plant available

silicon (Si). Studies have shown that rice straw at harvest should contain a

minimum of 3% Si for maximum rice grain production (Snyder et al., 1986). In a

greenhouse study used to evaluate the Si supplying ability of some Everglades

soils, it appeared that most soils supplied insufficient Si (Fig. 1), except for

one collected from near the lake (identified as Pahokee,'not to be confused with

the Series name "Pahokee"). We feel Si often is the element most limiting rice

production in the Everglades, Therefore, it is unlikely that responses to other

plant nutrients will be obtained unless the requirement for Si first is met.

To study this hypothesis, an experiment was conducted in 1986 at Okeelanta

Sugar Corporation. Lebonnet and Lemont rice received calcium silicate slag

pre-plant at 0, 5, and 10 Mg ha-1 (multiply by 889 for lbs A ). Plots

either received no mid-season nitrogen (N), or N at 100 kg ha- (multiply by

0.889 for Ibs A. ) from urea at panicle initiation. In retrospect, we now

feel the N rate was too high.

Most Lebonnet plots lodged severely, especially at the high Si and/or N

rates. Therefore, reliable data only could be collected from the Lemont plots.

However, this.experience points out the futility of trying to achieve high



*Professor-Soil Science and Assistant Professor-Rice Agronomy respectively,
Everglades Research and Education Center


Page 3







yields with Lebonnet; high yielding Lebonnet is very susceptible to lodging.

Lemont yields increased with increasing rates of slag (Fig. 2); 29% at the 10 Mg
-1
slag ha- rate. In the absence of slag, N fertilization had no significant

effect on yield. But at the high slag rate yield was increased 9% by N over the

"no N, 10 Mg slag" treatment, or 40% over the "no N, no slag" treatment. These

data demonstrate the necessity for supplying adequate Si in order to achieve

beneficial responses from other fertilizer nutrients.

In the Lemont ratoon crop of the above experiment, yield was increased 38%

by slag alone (Fig. 3). Application of N on the first crop (no N was applied to

the ratoon) increased yield 12% at the high slag rate, but no increase was

realized at the zero slag rate. A total ratoon crop yield increase of 54% was

obtained for the "10 slag-N" combination, compared to the "no N, no slag"

treatment. Clearly, the use of calcium silicate slag enhanced the response to N

in this study.

Some sheath blight (Rhizoctonia solani) was observed in the ratoon crop of

the above study. Plots that received slag had significantly less sheath blight

than check plots. However, slag does not provide total protection from sheath

blight; the authors lost the ratoon crop of a slag study to sheath blight in

1982 (Snyder, et al., 1986). Some reduction in disease, nevertheless, is

realized from having adequate plant Si.

Manganese Fertilization

A review of recent investigations on preventing manganese (Mn) deficiency

of drill seeded rice on high pH organic soils appeared in last year's Rice Field

Day Report (Snyder, et al., 1986). One of the studies discussed in that report

was completed.thereafter. In this study, MnS04.H20, sulfur, and tartaric acid

were drill seeded with cv. Lebonnet seed in a soil with pH 7.4. The sulfur and

tartaric acid were used to lower soil pH in an effort to improve availability of


Page 4







native soil Mn. Greater seedling dry weight production was obtained in plots

receiving MnSO4. Final grain yield was 33% greater in plots receiving Mn at

60 Kg ha-1 than in check plots (Fig. 4). Smaller yield increases were

observed for the other materials. Additional field tests have been established

this (1987) year.



References

Anderson, D. L., D. B. Jones, and G. H. Snyder. 1987. Response of a

rice-sugarcane rotation to calcium silicate slag on Everglades Histosols.

Agron. J. 79:531-535.

Snyder, G. H., D. B. Jones, and G. J. Gascho. 1986. Silicon fertilization of

rice on Everglades Histosols. Soil Sci. Soc. Amer. J. 50:1259-1263.

Snyder, G. H., C. L. Elliott, and D. B. Jones. 1986. Correcting rice seedling

micronutrient problems in the Everglades. Ninth Annual Rice Field Day,

Belle Glade EREC Research Report EV-1986-6.


Page 5











EFFECT OF SLRG ON RICE STRRW SI IN VARIOUS SOILS


SENINOLE SnELTON PRAOKEE OK-EAST OK-WEST iMM BRIDA


SOIL

Fig. 1. Si content of greenhouse grown rice straw as affected
by application of calcium silicate slag to soils from
various locations in the Everglades.


0 1 2 3 4 S 6
SLRG (MG/HR)


7 8 9 10


Fig. 2. Effect of pre-plant calcium silicate slag and
mid-season N on yield of 'Lemont' rice.


Page 6








WITH FIRST CROP N /Z

a: /

30 /




I -

;Z ^ ^^ NO FIRST CROP N

3009f I -- t -- ---


SLRG (MG/HR)

Fig. 3. Effect of pre-plant calcium silicate slag and
first crop mid-season N on ratoon crop rice
production.




EMNS04
SULFUR
S TRRTRRIC ACID


U) 4
cr



_j J


U-


-A


0 20 40 60 80 100
RRTE (KG/HR)


Fig. 4. Effect of drilling various materials with Lebonnet seed
on final grain yield.


Page 7









Update on Weed Control Methods in Rice Culture

J. A. Dusky*



NEW RICE HERBICIDES

Whip 1EC : Whip is a herbicide for use in the selective postemergence

control of annual and perennial grassy weeds in rice. Rice is tolerant to

postemergence applications of Whip from the 4-leaf to the late tillering stage

(but prior to panicle initiation) of rice development. Postemergence

application may result in temporary rice injury that appears as leaf chlorosis

and stunting on some varieties. The rice will normally recover from these

symptoms in two to four weeks. Whip is presently labeled in Arkansas,

Louisiana, Mississippi, Missouri, and Texas for rice production.

If rice is less than 8 inches in height, fields cannot be flooded for 7

days after the Whip applications. If rice is greater than 8 inches in height,

fields can be flooded in 4-5 days after application. The water depth cannot

exceed 25% of the crop height for 21 days after Whip application. Whip can be

applied after a permanent flood is established, but the flood should not cover

more than 25% of the rice and annual grass foliage.

Whip does not control any broadleaf weeds. Applications of other

herbicides may be made sequentially to Whip. Propanil should not be applied as

a tank mix or sequentially within 6 days of the Whip application. Whip should

not be used on rice varieties Mars or Leah.

Problems have been encountered using applications of Whip in rice under

Florida growing conditions. Severe stunting & chlorosis has resulted from

application of Whip to 'Lebonnet'. The rice was able to recover from the



*Associate Professor-Weed Science, Everglades Research and Education Center



Page 8






initial injury within 4 weeks after application, however, a delay in maturity

(10-14 days) resulted. Water management was extremely critical with the

application of Whip. It is absolutely critical that fields be level and that

water levels do not exceed 25% of the crop height when flooding occurs. Crop

injury was more severe when suggested water management regimes were not

followed. One:advantage to using Whip, which has not been evaluated under

Florida conditions, may be the application of Whip after the permanent flood has

been established but prior to panicle initiation for control of some grasses

such as fall panicum and goosegrass. However optimum stage of weed growth for

control of these species is 3-6 inches. Normally these weeds would exceed 6

inches at the time of permanent flooding.

At this time, under Florida rice growing conditions Whip does not appear

to be a viable option for weed control management. Cultural practices and

growing conditions in Florida such as land preparation, time of weed emergence,

timing of temporary or permanent floods, growth stages of weeds and rice, etc.

preclude the use of Whip in a weed management program.

Londa (DPX-F5384): Londax is primarily being developed as a

herbicide for control of broadleaf and sedge weeds normally found in

continuously flooded rice. There is excellent crop safety in both Japonica and

Indica type rice. Londax provides excellent control for 30-40 days, providing

water is not removed from the field for at least 4 days after application.

Evaluation of Londax in the U.S. has primarily been in California for water

seeded rice. Londax primarily controls aquatic weeds such as ducksalad,

ammannia, and waterhypsop. Londax is currently being sold in Thailand and

Indonesia and undergoing EUP testing in California. Water management is

critical for affective results.

BAS514: BAS514 is a herbicide being developed primarily for barnyard grass


Page 9






control in rice. BAS514 will control other annual broad leaf and grass weeds,

none of which are problem weeds in Florida rice production. BAS514 has been

found to provide excellent preemergence and postemergence control of

barnyardgrass, hemp sesbania, and morning glories, however, the compound must be

integrated into existing weed management programs to provide total weed

management.

BuctriP (bromoxynil): Buctril is a selective postemergence herbicide

for control of broadleaf weeds infesting small grains (wheat, barley, oats, and

rye). It is now being evaluated for use in rice. Optimum weed control is

obtained when Buctril is applied to small actively growing broadleaf weeds (2-8

leaf stage). Applications should be made soon after weed emergence. Buctril is

primarily a contact herbicide, therefore, thorough coverage is necessary for

optimum control. Buctril may be applied from emergence up to the boot stage in

small grains. Reduced control may occur when weeds are stressed.

Buctril is being evaluated for the first time in 1987. Dayflower

(Commelina sp.)'was the only broadleaf weed present in the plots and Buctril

provided excellent control. The advantages that Buctril may have in Florida

rice production for weed control is that it has a larger window for application

than 2, 4-D. Buctril can be applied from preemergence to the boot stage,

whereas 2, 4-D has to be applied after tillering and before internode elongation

paniclee initiation). Buctril is not as volatile as 2, 4-D, which would allow

for safe application in the spring of the year if applied properly. One of the

disadvantages of Buctril is that it will only control small weeds (2-8 leaf

stage) whereas 2, 4-D could be utilized with larger weeds.

Buctril may be extremely useful in weed management programs in Florida rice

production for broadleaf weed control. It would have to be integrated ;.i th be

use of other compounds for grassy weed control. More research is r-. '


Page 10









determine rates, time of application, weeds controlled, etc.

VOLUNTEER RICE CONTROL IN VEGETABLE CROPS

Studies were conducted in 1986 and 1987 to evaluate herbicides for

volunteer rice control. Emphasis has been placed on examining herbicides

presently utilized in vegetable crops and those that may be registered for use

in the near future. Linuron (Lorox) and prometryn (Caparol) were two herbicides

that were evaluated that are presently utilized for weed control in some

vegetable crops. The other compounds were graminicides or postemergence grass

herbicides that are presently being evaluated for registration in vegetable crop

production. The herbicides evaluated are listed in Table 1.

All the treatments were made postemergence when rice was in the 3-4 leaf

stage of growth. Rice vigor ratings were made and are shown in Table 1. Some

rate responses were observed. Select and Assure provided good control even at

the lowest rates utilized. Fusilade and Poast provided excellent control at

rates recommended for use in vegetable crops. The future registration of these

graminicides for use in vegetable crop production, will provide control of

volunteer rice when vegetable crop production is rotated with rice production.









The use of product trade names does not constitute a guarantee or warranty

of the products named and does not signify approval to the exclusion of similar

products.


Page :11







Table 1. Effect of vegetable crop herbicides and graminicides on rice.


Herbicide

Check
Fusilade
Fusilade
Fusilade
Poas t
Poast
Poast
BAS517
Assure
Assure
Select
Select
Lorox
Lorox
Caparol
Caparol
Verdict
Verdict


Rate (lb ai/A)


0.0625
0.125
0.25
0.1
0.2
0.3
0.125
0.0625
0.125
0.075
0.15
0.5
1.0
1.0
2.0
0.125
0.25


Page 12


Rice Control (%)

0
50
80
90
30
50
90
98
100
100
98
100
20
80
60
85
40
95






DD50 Rice Management Program: Theory and Use

Frank J. Coale*



The DD50 rice management program is a computer based decision making

aid for determining the optimum timing of production practices. Rice plant

development is controlled to a large degree by the amount of heat the plant i's

exposed to during the growing season. The research data base for relating air

temperature to rice plant growth and crop development was initiated in 1965 at

the University of Arkansas. This early work showed that the development of the

rice plant was related to the number of days in which the average air

temperature was above 50 F. The term "degree day" is used to measure the

thermal quality of a growing day. Degree Day 50 (DD50) refers to the number

of heat units that have accumulated during days in which the average daily

temperature was above 50 F. Research has determined how many accumulated

heat units (DD50s or accums) are required for a certain rice variety to

reach a particular growth stage. By utilizing historical temperature records

and by keeping a running account of the number of heat units that have

accumulated up to a given date, accurate predictions of the dates of future crop

development stages can be made.

DEGREE DAY CALCULATION

Rice growth and development is extremely limited below 500F and this

temperature is used as the low-temperature cut-off threshold for DD50

calculations. Plant growth is also limited during days with daytime maximum

temperature exceeding 94 F and nighttime minimum temperatures exceeding

70 F. The heat units generated during days with either daytime maximum or



*Assistant Professor-Extension Agronomist, Everglades Research and Edbat.io
Center


Page 13





nighttime minimum temperatures exceeding these limitations are adjusted.

DD 0s are calculated by averaging the maximum daily high temperature

(T max) and the minimum daily low temperature (Tmin) in degrees

Fahrenheit and subtracting 50 (the low-temperature threshold):


T + T
max min
DD = ----------- 50.
2
If the daily high temperature exceeds 940F, it is assigned 94 F. If the

daily low temperature exceeds 70 F, it is assigned 700F.

The temperature information used to calculate DD50s for the Florida

rice industry is collected at the weather station at the Everglades Research and

Education Center, Belle Glade. The number of DD50s needed to reach each of

the critical growth stages of the rice plant, the 10-year weather data base, and

the current year-to-date DD50 accumulations are a permanent part of the

computer program. Knowing the planting date or, even better, the date of

emergence of a particular field, enables the program to provide a producer with

predictions on when plants in that field will reach certain growth stages. The

initial prediction is based on average temperatures and accumulated DD50s

over the past 10 years. Year-to-date DD50s are used to update predictions

based on specific weather conditions that have prevailed during the particular

growing season.

The DD50 program currently being evaluated for Florida rice production

is based on a program provided to the Louisiana rice producers by the Louisiana

Cooperative Extension Service. Below is a reproduction of the information input

portion of the DD50 program and the predicted date of specific growth stages

output that was generated.


Page 14







IMMMMMMMMMMMMM;
: DD50 MENU :
HMMMMMMMMMMMMM<

1 CALCULATE DD50

2 CREATE/CHANGE WATER DATA FILES

3 PRINT WATER STATION DATA FILES

4 STOP EXECUTION


Make selection (1- 4 ) ?








*****************************************************

LADD5086.BAS

* A RICE MANAGEMENT AID FOR LOUISIANA AGRICULTURALISTS *

* LOUISIANA COOPERATIVE EXTENSION SERVICE AND NATIONAL *
* WEATHER SERVICE COOPERATING *
* *
*THIS PROGRAM IS DERIVED FROM RESEARCH AND RECOMMENDATIONS *
*OF THE UNIVERSITY OF ARKANSAS AND THE NATIONAL WEATHER *
*SERVICE, STONEVILLE, MISSISSIPPI. SUBSEQUENT APPROVAL AND*
*TESTING HAS BEEN COMPLETED BY LOUISIANA STATE UNIVERSITY *
*AND THE NATIONAL WEATHER SERVICE, MID-SOUTH AGRICULTURAL *
*WEATHER SERVICE CENTER AT STONEVILLE, MISSISSIPPI. *
* NOTE *
*STARBONNET, LEBONNET, LABELLE, MARS, LEMON, SATURN, *
*BOND, NEWBONNET, AND TEBONNET ARE THE ONLY VARIETIES IT *
*WILL WORK ON. FOUR TEMPERATURE FILES MUST ACCOMPANY THIS *
*PROGRAM LISTING. CONTACT YOUR PARISH AGENT IF YOU HAVE *
*QUESTIONS ABOUT LADD5086.BAS.


ARE YOU READY TO PROCEED (Y OR N)?


Page 15










ARE YOU READY TO PROCEED (Y OR N)? Y

PROGRAM IS INITIALIZING. INSTRUCTIONS WILL FOLLOW

ENTER FARMER/AGRICULTURALIST NAME? FRANK COALE

ENTER ROUTE, P 0 BOX, STREET, ETC OF ADDRESS? P 0 DRAWER A

ENTER CITY, STATE,.AND ZIP CODE? BELLE GLADE FL 33414

WHICH WEATHER DATA SET SHOULD BE USED? ? BG87

WEATHER DATA READ INTO PROGRAM

IS THIS FIELD WATER SEEDED (Y OR N)? N

WHAT IS THE CURRENT DATE (MM-DD-YY)? 07-10-87

HOW MANY FIELDS THIS RUN (LIMITED TO 4)? 1

ENTER THE GROWTH STAGE FROM WHICH YOU WANT TO PREDICT FROM.
CODES ARE:EFFECTIVE PLANTING=1; DATE OF EMERGENCE=2; FIRST
TILLER=3; OR HEADING=7. MUST BE ENTERED CORRECTLY.? 1

WHAT IS THE FIELD NAME (LIMITED TO 10 LETTERS)? EREC 4E

HOW MANY ACRES ARE IN THIS FIELD? 20

WHAT IS THE VARIETY? LEBONNET

WHAT IS THE GROWTH STAGE OCCURRENCE DATE(EXAMPLE MAY 5=5,5)? 3,8


Page 16















FRANK COALE P 0 DRAWER A BELLE GLADE FL 33414


RICE GROWTH AND MANAGEMENT PREDICITIONS-07-10-87

EVERGLADES RESEARCH AND EDUCATION CENTER

BASED ON A PROGRAM DEVELOPED BY THE
LOUISIANA COOPERATIVE EXTENSION SERVICE

WEATHER DATA SET BG87
******************************** k******************* *
FIELD NAME EREC 4E
ACRES 20
VARIETY LEBONNET
*******************************************************************************

EFFECTIVE PLANTING DATE 3 8
DATE OF EMERGENCE *1 3 20
FIRST TILLER *2 4 24
BEGIN CHECKING INTERNODES *3 5 16
CHECK FOR PANICLE INITIATION *4 5 26
EARLY BOOT *5 6 11-
HEADING *6 6 21
HARVEST. *7 7 26
********************************************************************************
PREDICTIONS ARE BASED ON RESEARCH FROM THE UNIVERSITY OF ARKANSAS AND LSU.
THESE ARE ONLY PREDICTIONS, SO FIELDS MUST BE CHECKED CAREFULLY TO ASSURE THAT
PLANTS ARE AT PROPER GROWTH STAGES.
*1. EMERGENCE EQUALS 8-10 SEEDLINGS VISIBLE PER SQUARE FOOT FOR DRILL SEEDED
RICE AND SEEDLINGS AROUND 3/4 INCH (AVERAGE) FOR WATER SEEDED RICE.
IF PROPANIL IS USED IT SHOULD BE APPLIED NO LATER THAN THE 2-3 LEAF
STAGE OF RICE. BEGIN FLOODING WITHIN 24 HOURS OF APPLICATION. DURING
COLD-CLOUDY WEATHER, DELAY FLOOD 2-3 DAYS TO ENHANCE PROPANIL ACTIVITY.
*2. MAJORITY OF PLANTS DISPLAYING FIRST TILLER. UNDER NORMAL CONDITIONS,
A FIELD SHOULD BE PERMANENTLY FLOODED BY THIS TIME. BEGIN SCOUTING FOR
RICE WATER LARVAE (ROOT MAGGOTS) WITHIN 10 DAYS AFTER THE PERMANENT
FLOOD IS APPLIED. CONTINUE COUNTING .UNTIL FIELD IS TREATED OR PANICAL
INITIATION STAGE IS REACHED.
*3. BEGIN CHECKING FOR INTERNODE ELONGATION (GREEN RING) STAGE.
PHENOXY HERBICIDES SHOULD BE APPLIED AT THE FIRST GREEN RING. DO NOT
APPLY AFTER THE SECOND GREEN RING STAGE. (NOTE: THIS ALLOWS ONLY
A 7-10 DAY WINDOW FOR PHENOXY APPLICATION)
*4. PANICLE INITIATION (FIRST INTERNODE 1/2 INCH TO 3/4 INCH DEPENDING
ON VARIETY). NO PHENOXY HERBICIDES SHOULD BE APPLIED AFTER THIS DATE
*5. EARLY BOOT IS WHEN THERE IS ONE TO TWO INCH PANICLE IN THE BOOT. THE
FIRST FOLIAR FUNGICIDE APPLICATION FOR BLAST AND/OR SHEATH BLIGHT
SHOULD BE APPLIED (IF NEEDED). WITH VARIETIES HIGHLY SUSCEPTABLE TO
SHEATH BLIGHT (LEMONT, LABELLE, LEBONNET), TREAT WHEN
5 (OR GREATER) PERCENT OF THE TILLERS ARE DISPLAYING LESrONS. WITH NEW-
BONNET, STARBONNET, AND TEBONNET, THE THRESHOLD IS 15% OR GREATER.
*6. HEADING IS WHEN 75% OF THE STEMS ARE SHOWING HEADS. APPLY SECOND FOLIAR
FUNGICIDE APPLICATION. BEGIN SCOUTING FOR RICE STINK BUGS. TREATMENT
THRESHOLDS ARE 30 OR MORE PER 100 SWEEPS DURING THE FIRST 14 DAYS AFTER
HEADING AND 100 PER 100 SWEEPS FROM 15 DAYS AFTER HEADING UNTIL HARD DOUGH
STAGE IS REACHED.
*7. HARVEST IS WHEN A GRAIN SAMPLE IS AROUND 20% MOISTURE.
CONTACT YOUR COUNTY AGENT FOR ADDITIONAL INFORMATION.


Page 17






DD50 Rice Management Program:

Importance of Various Predicted Growth Stages

D. B. Jones*



The DD50 program currently in limited use at Everglades Research and

Education Center is a modification of the program developed by Louisiana State

University. As we gain more information to develop a local data base the

program will be further modified to increase the accuracy of predictions of

various growth stages. In addition, as we develop management practices unique

to EAA rice production, they will be added to the program. There are currently

eight dates included in the program. A discussion of the importance of these

dates/growth stages with respect to crop management in the EAA follows:

EFFECTIVE PLANTING DATE

Although "effective" planting date and "actual" planting date are

frequently the same, there is a significant difference on some occasions.

Planting is the act of placing the seed in the ground, yet for the basis of

predicting the time interval between planting and emergence, the soil must be in

sufficient condition to allow the seed to begin germination after it has been

placed. In cases where the seedbed is extremely dry, germination will not begin

until adequate moisture is available. Once moisture becomes available either

through flushing the field or a rainfall, germination will begin, and this date

is then the "effective" planting date, even though it may be several days after

the actual planting date. In most cases in the EAA, the "effective" and actual

planting dates are the same. The DD50 program allows for 180 units for all

varieties from effective planting date to emergence.



*Assistant Professor-Rice Agronomist, Everglades Research and Education
Center


Page 18






DATE OF EMERGENCE

The date of emergence is considered to be when 8-10 seedlings have emerged

per square foot of row. With rice drilled in 7 inch rows, a square foot is

equivalent to approximately 20 inches of row, therefore 8-10 seedlings/ft2

would be approximately 1 seedling/2 inches of row. This date is critical for

accurate DD50 predictions. Although a planting date can be used as a

starting point for DD50, there can be considerable variation between time

from planting to emergence for reasons discussed above. This variation in time

will persist throughout the rest of the DD50 predictions. However, if

emergence date is used as a starting point, these variations can be eliminated,

and the accuracy of predictions will be improved.

FIRST TILLER

The first tiller usually emerges from the sheath of the first true leaf,

just prior to or when the fifth leaf emerges. Plants will normally be 4-6

inches in height at this time. This date is important in that fields should be

permanently flooded by this time. Contrary to some beliefs, rice does tiller

when flooded. Flooding only reduces tillering when the flood is excessively

deep -- over 6-8 inches. Rice water weevils can be a problem in EAA rice,

particularly when it is planted late, and in areas of thin stands and/or deep

water. Scouting for rice water weevil larvae should begin within 10 days after

the permanent flood is applied. If 5 or more larvae are found per 4 inch core

sample, fields can be drained to control the larvae. This treatment can be used

at any time until the panicle initiation stage is reached.

BEGIN CHECKING INTERNODES

This DD50 date indicates when the plant is nearing the panicle

initiation stage. A well defined crown should be apparent when the plant is

split in half at the base. In some cases a distinct area of the crown will have


Page 19







a darker green color than the rest of the crown. This is called the "green

ring" stage. Sometimes this green ring is difficult to detect though, therefore

it is better to recognize this stage by the condition of the crown of the plant.

The nodes should be recognizable, with little or no elongation of the internode.

This stage is significant for several reasons. If a phenoxy type herbicide (ex.

2, 4-D) is to be used, it can only be used safely during a 10 day period

beginning at this stage, otherwise the rice may be injured. If a grower

practices mid-season draining, the field should be reflooded at this time to

avoid damage to the panicle. If a grower wishes to apply nitrogen, this is the

best time to do so.

CHECK FOR PD PANICLEE DIFFERENTIATION)

Panicle differentiation (PD) is the stage at which the panicle begins to

form distinct parts such as branches and florets. Although these parts cannot

be seen with the unaided eye, the panicle itself can. It will be approximately

1/8 inch long and will appear as a small tuft of fuzz at the growing point of

the plant. This stage is most easily recognized by splitting the stem

lengthwise and observing the length of the internode. PD occurs when the

longest internode is 1/2 3/4 inch in length, depending upon the variety. At

PD the field should be flooded, and remain flooded until draining for harvest.

It is also the cut-off date for phenoxy herbicides and mid-season N application.

EARLY BOOT

Booting is when the upper portion of the stem begins to swell. It is

caused by the growth of the immature panicle inside of the leaf sheath. Early

booting can be recognized when the collar of the flag leaf (the last leaf to

appear before the panicle emerges) and the penultimate leaf (leaf below the flag

leaf) are aligned. This occurs roughly two weeks after PD and two weeks before

heading. The first foliar fungicide application should be made at this time.


Page 20






HEADING

Heading is when 75% of the plants in a stand have emerged panicles. This

is the beginning of the grain filling period. The second foliar fungicide

application should be made at this time. Scouting for rice stink bugs should

also begin at heading and continue until harvest. The grain filling period is

less affected by temperature than the other growth stages previously discussed.

For most varieties, the grain filling period lasts approximately 35 days.

HARVEST

Rice is mature and ready to harvest, when 90 100% of the filled grains

are hard and yellow. The grain moisture should be around 20%.


Page 21






APE2!D'.


A Chronology of Rice Research


Everglades Research and Education Center
Belle Glade, Florida



Shih, S. F., G. S. Rahi, G. H. Snyder, D. S. Harrison, and A. G. Smajstrla.
1983. Rice yield, biomass, and leaf area.related to evapotranspiration.
Transactions of the American Society of Agricultural Engineers.
26:1458-1464.


Alvarez, J. and G. H. Snyder. 1984. Effect of prior rice culture on sugarcane
yields in Florida. Field Crops Research. 9:315-321.


Cherry, R. H., D. B. Jones, and F. W. Mead. 1986. Leafhoppers (Homoptera:
Cicadellidae) and planthoppers (Homoptera: Delphacidae) in southern Florida
rice fields. The Florida Entomologist. 69:180-184.


Snyder, G. H., D. B. Jones, and G. J. Gascho. 1986. Silicon fertilization of
rice on Everglades histosols. Soil Science Society of America Journal.
50:1259-1263.


Jones, D. B. and R. H. Cherry. 1986. Species composition and seasonal
abundance of stink bugs (Heteroptera: Pentatomidae) in south Florida rice.
Journal of Economic Entomology. 79:1226-1229.


Anderson, D. L., D. B. Jones, and G. H. Snyder. 1987. Response of a
rice-sugarcane rotation to calcium silicate slag on Everglades histosols.
Agronomy Journal. 79:531-535.


Page 22





Rice Yield, Biomass, and Leaf Area

Related to Evapotranspiration



S. F. Shih, G. S. Rahi, G. H. Snyder, D. S. Harrison, A. G. Smajstrla


MEMBER
ASAE


MEMBER
ASAE


MEMBER
ASAE


ABSTRACT
STUDIES on the relationships among evapotranspiration
(ET), grain yield, dry biomass, and leaf area index
(LAI) of rice were conducted in lysimeters and in the
field. Two methods of planting rice were used:
transplanting and direct seeding. There were twelve
planting combinations involving spring, summer, and
fall crops. Three equations involving linear leaf
measurements and stem length were developed to
estimate the LAI. Peak .ET rates occurred during the
reproductive stage and coincided well with the maximum
LAI value. Two equations involving dry biomass and
grain yield in relation to ET were also developed. The
relationship between dry biomas (DB) and ET was found
to be: DB = 4715.2 + 303.1 ET. Grain yield (rough
rice at 12% moisture, GY) was related to ET as:
GY = 3995.8 + 174.9 ET. With an average rice yield
in the Everglades of Florida, the total ET requirement
would be about 54 cm.

INTRODUCTION
The Everglades Agricultural Area (EAA) consists of
about 200,000 ha of fertile organic soil. When these
organic soils are drained, they subside about 2.5 cm a
year (Stephens, 1956) primarily because of the microbial
oxidation. The subsidence rate can be reduced if high
water tables are maintained or if the land is flooded.
Based on current subsidence rates, 87% of the EAA will
have soil less than 90 cm deep by the year 2000. A crop
such as rice (Oryza sativa L.) which grows well under
flooded conditions could be considered as an alternative
crop for this area to reduce subsidence and preserve the
organic soil.
Previous studies have shown that rice can be grown on
flooded organic soils in the EAA (Green, 1953, Alvarez
et al., 1980). Rice can be produced as a summer crop
along with either a sugarcane or vegetable crops in
rotation. In the EAA, rice can be planted from March
through mid-August. About 100 ha of rice were planted
in the EAA by one grower in 1977 and 4000 ha were
planted by eight growers in 1981. Because of the trend of
increased rice production within the EAA, a study was
initiated to investigate the water requirement of the rice
crop.
Article was submitted for publication in December, 1982; reviewed
and approved for publication by the Soil and Water Div. of ASAE in
March, 1983. Presented as ASAE Paper No. 82-2597.
Florida Agricultural Experiment Station Journal Series No. 4079.
The authors are: S. F. SHIH, Professor. G. S. RAHI, Research
Associate, D. S. HARRISON. Professor, and A. G. SMAJSTRLA,
Associate Professor, Agricultural Engineering Dept., University of
Florida, Gainesville; and G. H. SNYDER, Professor, Agricultural
Research and Education Center, University of Florida, Belle Glade.
Acknowledgments: This study was partially supported by a grant
contract No. 4-FCD-22 from the South Florida Water Management
District. The authors also thank Mr. W. L. Cheng, and Mr. Norman L.
Harrison for their assistance in this study.


Uneven rainfall distribution in Florida creates a
critical water-resource management problem. For
example, the yearly rainfall cycle in south Florida
consists of a warm rainy season from May 'through
October during which about 75% of the total rainfall
occurs followed by a relatively dry winter season. In some
years, the dry season develops into an extended drought
which increases irrigation requirements. To cope with
this water-resource problem, the rice evapotranspiration
(ET) rate needs to be investigated further whether it
would vary with growth stage. Mainly because if the rice
ET will vary with the growth stage, planting date could
be adjusted so that the period of peak ET requirement
would not coincide with last part of the dry season in the
EAA. Variations in rice ET with growth stage have been
studied by several researchers. Chapman and
Kininmonth (1972) reported that rice ET was maximum
at the reproductive stage. However, Wickham and Sen
(1978) indicated that the increase in the ET during the
reproductive stage was attributable to climatic changes,
and not to the crop growth stage. Evidence is inclusive
about whether the rice ET would vary with the growth
stage. Therefore, in this study, the relationship among
leaf area index (LAI), ET and the ratio of ET to
Standard Class A pan evaporation (SPE) was used to
investigate the rice ET whether it would change with the
growth stage.
Another important aspect studied was the relationship
between rice yields and ET. For many crops, ET has
been shown to be directly relAted to dry matter and grain
yield production when factors such as fertility, sunshine,
temperature and soil moisture are not limiting (Allison et
al., 1958; Hillel and Guron, 1973; and Stewart et al.,
1975). However, the available literatures show that
previous research studies have not emphasized the
relationship between rice yields and ET.
The objectives of the present studies were to (a)
develop a fast and reliable technique for rice LAI
estimation; (b) determine ET as related to the LAI and
the growth stage; (c) investigate whether the ratio of ET
to SPE would vary with the growth stage; (d) develop
relationships for both rice dry biomass (DB) and grain
yield (GY) with ET.

MATERIALS AND METHODS
Experimental Site
Studies on rice were conducted on Pahokee muck
(Lithic medisaprist) at a lysimeter and a field site. Two
types of lysimeter systems were installed at the lysimeter
site: concrete lysimeters and metal-drum lysimeters. In
1979, these lysimeters were surrounded by St. Augustine-
grass (Stenothaphrum secundatum), whereas, three rows
of sugar cane (Saccharum spp.), about 4.5 m wide, were
grown around the lysimeter site to minimize the oasis
effect in 1980.


1458 1983 American Society of Agricultural Engineers 0001-2351/83/2605.1458502.00


TRANSACTIONS of the ASAE--1983





The concrete lysimeters consisted of nine reinforced
concrete tanks (183 cm long, 122 cm wide, and 122 cmi
deep) installed at the University of Florida, Agricultural
Research and Education Center (AREC) in Belle Glade.
The tanks were installed about 67 cm into the ground
with about 55 cm protruding above the ground surface.
Six lysimeters were used to grow rice and the remaining
three were fallow flooded for monitoring evaporation.
The metal-drum lysimeters consisted of six metal
drums (46 cm deep and 57 in diameter) installed
adjacent to the concrete lysimeters. Four of the six drums
were designated as ground level drums which were
installed about 25 cm under ground and protruded about
21 cm above ground. Two of the ground level drums were
used to grow rice, while two remained as flooded bare
soil drums. The remaining two of the total six drums
were designated as raised level drums which were set up
on a raised platform so their top surface was at the same
height as the concrete lysimeters (i.e. 55 cm above the
ground surface). Rice was grown in the two raised level
drums. Since the water level was maintained at 5 to 8 cm
above the soil surface, the amount of water applied and
the excess rainfall released for maintaining the 5 to 8 cm
water level were operated manually.
Only metal drums were used at the field site which was
located about 1,200 m from the lysimeter site. Nine
metal drums (46 cm deep and 57 cm diameter) were
installed in a one-half ha rice field to minimize the oasis
effect. The drums were buried about 25 cm into the
ground with about 21 cm above ground. Seven drums
were used to grow rice and the remaining two were fallow
flooded.
Rice was either transplanted or seeded directly. One-
month old seedlings were transplanted at spacing of 2.5
cm within a row and 25 cm between rows. Direct-seeded
rice was spaced 1.3 cm' within a row and 25 cm between
rows. The seed was drilled about 2.5 cm deep and the soil
was irrigated to induce germination. The amount of
water applied was recorded, and the direct-seeded plots


were continuously flooded when plants were about 5 cm
tall. The transplanted plants were flooded immediately
after transplanting because these plants were taken from
a seeded field that was already flooded. The water level
was maintained at 5 to 8 cm above the soil surface.
The rice cultivar 'Lebonnet' was grown in 1979 and
1980. Twelve planting combinations encompassed the
three seasons of spring, summer and fall. The dates of
planting, flooding, and harvesting are listed in Table I.
In experiment No. 6, an additional planting combination
of direct seeding with three replications was used in
concrete lysimeters to study ET in relation to the LAI for
the direct-seeded crop. Direct seeding for, this
combination was done on July 7, 1980 and the crop was
harvested on September 16 before reaching maturity,
because the lysimeters were needed for winter vegetables.

Leaf Area Index Estimation
Stem population, leaf area and leaf linear
measurements, leaf area per stem, and LAI calculations
were sampled in concrete lysimeters in 1980 for both
methods of planting. The sample was taken
undestructively from the lysimeters. In the crop which
was transplanted from one-month old seedlings on July
7, measurements were made at 48, 70, 82, and 97 days
after planting. In the crop which was direct seeded on
July 7, measurements were made at 43, 55, and 70 days
after seeding.


Stem Population: At each time of sampling, one row
was randomly selected from each concrete lysimeter and
stem populations were counted. The stem population
was then calculated per square meter area.
Leaf Area and Linear Measurements: In this study,
the leaf refers to the blade portion only. Twelve leaves
were randomly selected from each concrete lysimeter at
the time of sampling. The leaf area was measured with
an electronic foliometer (Hatfield et al., 1976). Length of


TABLE 1. TREATMENT DATA AND YIELDS OF RICE GRAIN AND DRY BIOMASS FOR TWELVE PLANTING SCHEMES
IN 1979 AND 1980.
Yields Grain and
Growth Dry dry biomass
Crop Exp. Type of Planting Flooding Harvest period, Grain, biomass, ratio,
Season No. Site Year planting date date date day Rep. kg/ha kg/ha %
1 L.D. 1980 SP-G 3/6 3/28 7/7 123 2 9,369 20,065 47.7
Spring 2 SP-R 3/6 3/28 7/7 123 2 9,900 21,567 45.9
3 F.D. 1980 SP 3/6 3/28 7/7 123 2 9,369 19,976 47.0
4 1979 TP 4/22* 5/22 8/9 109 3 10.658 19,393 55.0
6 C.L. SP 5/20 6/4 9/6 109 3 11,241 20,226 55.6
Summer 6 1980 TP 6/7* 7/7 9/16 101 3 6,207 14,081 44,1
7 1979 TP-G 6/20* 7/20 10/11 113 2 N.D. 19,199 -
8 L.D. TP-R 6/20* 7/20 10/11 113 2 N.D. 18,562 -
9 F.D. 1979 TP 6/20* 7/20 10/11 113 2 N.D. 11491 -
10 L.D. 1980 SP-G 8/10 9/2 11/17 99 2 N.D. 8,132 -
Fall 11 SP-R 8/10 9/2 11/17 99 2 N.D. 10,872 -
12 F.D. 1980 SP 8/10 9/2 11/17 99 3 3,951 8,309 47.6
L.D = Metal drum in lysimeter site, F.D. = Metal drum in field site, C.L. = Concrete tank inlysimetersite, SP = Direct seeded crop, TP
Transplanted crop.
SP-G Direct seeded crop at the ground level of L.D.
SP-R = Direct seeded crop at the raised level of L.D.
TP-G = Transplanted crop at the ground level of L.D.
TP-R = Transplanted crop at the raised level of L.D.
* Planting date for the transplanted crop was approximately one month before the transplanting date.
N.D. = No data.


1983-TRANSACTIONS of the ASAE





the leaf and maximum width of each leaf were also
measured.
Total Leaf Area Per Stem: Three stems were randomly
selected from each concrete lysimeter at each time of
sampling. The stem length was measured from the
ground surface to the flag leaf. The total leaf area for
each stem was measured by the electronic foliometer.
Leaf Area Index: Twenty stems were randomly
selected from each concrete lysimeter at each time of
sampling. The stem length was measured from the
ground surface to the flag leaf. The stem lengths were
used to estimate the total leaf area for each stem from a
model to be discussed later. The leaf area index was
computed by multiplying average leaf area per stem by
the number of stems per square meter, then dividing by
the area of square meter.

Evapotranspiration and Yield
Evapotranspiration: Water budget for each unit was
monitored at 8:00 a.m. daily except on weekends and
holidays. When heavy rainfall occurred, measurements
were also made during the weekend. The SPE data were
obtained daily from the AREC Weather Station (located
about 30 m from the lysimeter site).
The total ET for the entire growing season was
estimated using two procedures. For the direct-seeded
crop, ET was calculated directly from the recorded data.
For the transplanted crop, the ET was calculated from
the water used for both before and after transplanting.
The ET after transplanting was recorded from the day
the plant was transplanted. However, the ET before
transplanting (one month old) was not available. Thus,
the ET before transplanting was estimated by modifying
the SPE data during the month preceding the
transplanting date. The modification procedure is
defined as the SPE times a ratio. The ratio was computed
as the water used in the first month by the direct-seeded
crop divided by the SPE over the same period.
The lysimeter site had environmental conditions
different from those of the field site. To adjust for these
differences, a conversion factor (CF) was used to
normalize the ET data collected at the lysimeter site with
respect to the ET observed in the field. The CF value
used for each growth season was estimated from an
average of 30 randomly selected ratios between k, and kz,
where k, and k2 were the daily evaporation values from
fallow flooded containers at the lysimeter and field sites,
respectively.

Grain Yield and Dry gin r'.-s: The grain and total
above-ground biomass were hand harvested from all
lysimeters. The grain was air dried for 15 days. After air
drying, the grain contained about 11 to 12% moisture by
weight. Thus, the grain yield in this study is referred to
the rice grain with 12% moisture by weight. The dry
biomass yield containing both stem and grain was
measured after drying at 70 C for 5 days.

Model Descriptions
Leaf Area Estimation: The following relationship
between leaf area and leaf linear measurements (length
and width) is commonly used for leaf area estimation:

A =m L W .............. .... ........... [

where

1460


A =leaf area. cm2
L =length of leaf, cm
W = maximum width of leaf, cm
m = constant
The m value was estimated from the experimental data
of leaf area measured by electronic foliometer and linear
measurement of the leaf. A simple and rapid technique
introduced in this study is the estimation of the leaf area
from leaf length alone, i.e.
A =nL2... .. . . . . . . ....2]

Where A and L are as previously defined and the n is a
constant. The n value was estimated frbm the
experimental data of leaf area measured by electronic
foliometer and the measured length of leaf.
Recently, Shih and Gascho (1980) developed and
tested a mathematical relationship between sugarcane
stalk length and leaf area so that the total leaf area per
stalk can be directly estimated from the stalk length, i.e.


y ...................... [3]

where
Y = total leaf area for each stalk, cm2
X = the length of the stalk, cm
a,b,c = coefficients
An important feature of this model is that the leaf area
per stalk declines after reaching a maximum. Regression
analysis between stalk length and total leaf area per stalk
was used to estimate a, b, and c from the experimental
data.

Evapotranspiration Measurement
The evapotranspiration for each lysimeter unit was
determined based on the following water budget
equation:
ET I+ R ....................... [4]

where
ET = evapotranspiration
I = water applied to the system
R = rainfall on the system
O = excess rainfall released from the system
The daily ET was computed from the daily water budget
data except that the ET on weekends and holidays was
computed together with the preceding date. For
example, the ET on Saturday and Sunday were
combined together with the ET on Friday. Thus, the ET
for rice production were estimated based on two time
intervals, i.e. weekly and the entire growth periods. The
weekly periods extended from Fridays through
Thursday.

S."rpodi-r[ir. tion and Yield Relations
A linear regression model was used to express the
relationship between ET and yields.
For dry biomass:

DB = ao +a, ET ...................... ... [51

For grain yield:

GY =bo +b, ET ................ ............ [6]


TRANSACTIONS of the ASAE-1983






where
DB = dry biomass, kg/ha
GY = grain yield, kg/ha
ET = evapotranspiration, cm
a, = the rate of increase in dry biomass production
in relation to ET, kg/ha per cm ET
b, = the rate of increase in grain yield production
in relation to ET, kg/ha per cm ET
ao and bo constants.
Regression analysis was used to estimate ao, a,, bo, and
b, from the experimental data.

RESULTS AND DISCUSSION
Leaf Area Estimation
Leaf linear measurements and electronic foliometer
measurements for a total of 252 leaves were analyzed.
The coefficients, m and n, presented in equations [1] and
[2] were calculated and the result for equation [1] was:

A = 0.731 L W (r = 0.97). ................. ... [7

The correlation coefficient between foliometer
measurements and model prediction indicates that the
rice leaf area can be closely estimated from the linear
measurements of length and width of the leaf.
The result for equation [2] was:
A = 0.028 L2 (r = 0.80) ..................... .. 8]

The correlation coefficient for this model as presented in
equation [8] is 0.8 which is lower than that of the value
presented in equation [7]. However, equation [8] is
relatively easier to use for measurement.
A total of 63 plant measurements of stem length and
total leaf for each stemware shown in Fig. 1. The resulting
coefficients for equation [3] were:

x
Y Exp- 0.86)
1E .806+ 0.136 X + 4.478x 10- X ( 0.86)

................. .................... .. [9

The F-test indicated that the coefficients 1.806, 0.136
and 4.478 x 10"4 were all significant at the 0.01 level,
demonstrating that rice leaf area per stem can be
expressed as a function of stem length by an exponential
relation with a hyperbolic-limiting argument. The
simulated results from equation [9] represent a general
relationship between leaf area and stem length (Fig. 1).
Leaf area per stem declined slightly after stem length
reached about 60 cm for cultivar 'Lebonnet'. This is
consistent with the general pattern of rice leaf area which
begins to decline as the plant approaches the
reproductive stage.
It needs to be noted that as mentioned in the previous
section of sampling procedures, the total leaf area per
stem were sampled during the plant age between 43 and
97 days. As Table 1 shows, the growth period of No. 6
experiment which was used to conduct the sample was
101 days. In other words, the total leaf area per stem was
measured toward the end of growth season (i.e. 4 days
before harvesting). However, the data for the early
growth stage (before 43 days of plant age) was not
sampled in this study, mainly because the plant was too
small to be sampled undestructively by using the area
foliometer. Furthermore, the plant reached to th; full


LLJ K [[XAc,,o6 36Xoex 478e,,o-4X1Z
-
S 10 o *

S7C .. R2-o.86

& so-




St40 So 60 70 60 9
STEM LENGTH-X, cm
Fig. 1-Relationship between rice stem length and total leaf area per
stem.

canopy condition (i.e. the LAI is greater than one) is
mainly interested in this study which will be discussed
later. If a user is interested in the LAI estimation for the
early stage of growth, the sample could be done
destructively and coefficients used in the equation [9]
might need some modifications.
As above equations [7], [81, and [91 show, the equation
[9] is a relatively easy method used to estimate the total
leaf area per stem, mainly because the total leaf area per
stem can be directly estimated from the stem length.
However, in practical application, the coefficients used
in equation [9] could be varied with location, cultivar,
etc. Thus, if a user intends to develop a new set of
coefficients of equation [9] for using in a specific area
and cultivar, whereas a foliometer is not available during
the time of sampling, either equation [7] or [8] could be
used to estimate the leaf area for each leaf. Based on the
information of the summation of leaf area in each leaf
per stem and the stem length, a hew set of coefficients for
equation [9] could be developed.

Leaf Area Index (LAI)
The measured stem length and stem population as a
function of age of plants for the transplanted crop and
direct seeded crop are listed in Table 2. Equation [9] was
used to estimate the total leaf area per stem. The
maximum leaf area index of about 5 was reached at
approximately 70 days, then declined to about 4.5 at
approximately 100 days after planting.

Evapotranspiration Calculation
The average CF values as defined earlier for the
summer crops were 0.68 in 1979 and 0.78 in 1980. The
higher ratio for CF in 1980 was probably caused by
reduction in the oasis affect by growing sugarcane
around the lysimeter site in 1980. The average CF values
for spring and fall crops in 1980 were calculated as 0.81
and 0.82, respectively. The deviations for estimating the
average CF value for each growth season are all within
the range of 0.01. Those CF values were used to
normalize the ET data gathered at the lysimeter site in
relation to the ET observed in the field site. The ET data
of the lysr:.eter site represent the normalized results
hereafter.
The weekly ET data of the lysimeter site, and the field
site data for different growing seasons were calculated


1983-TRANSACTIONS of the ASAE






TABLE 2. RICE STEM LENGTH, TOTAL LEAF AREA PER
STEM, STEM POPULATION, AND LEAF AREA INDEX (LAI).*

Estimated
Age of Stem Stem total leaf
Type of plants, length, population, area per stem,
planting days cm stem/m' cm2 LAI

Trans- 48 22.8 285 84.4 2.40
planted 70 67.3 283 178.5 5.05
crop 82 77.1 265 174.0 4.60
97 79.4 266 172.3 4.58
Direct 43 20.5 241 72.8 1.75
seeded 55 25.9 281 100.0 2.82
crop 70 62.0 251 178.9 4.50

Data are averages of 3 replications of concrete lysimeters.
T The transplanted crop is same as experiment No. 6 listed in Table
1. The direct seeded crop is an extra planting combination which
was not listed in Table 1.


based on the method presented in equation [4]. The
weekly ET was limited to the flooded period only. An
average of daily ET in each week was calculated from the
weekly ET. The range and mean value for the weekly ET
are shown in Table 3. The ranges of weekly ET varied
from 1.3 to 8.2 cm/week. The ET data for the total
growth period was summarized from the weekly ET and
the ET for the period before either flooding or
transplanting. The results of range and mean values for
the total ET are also shown in Table 3. The total ET
requirement for rice production varied from 39.3 to 88.2
cm.

Relationship Between Evapotranspiration and
Leaf Area Index
Since the LAI was estimated periodically, the mean


i

; ---- _
/ d


o / 2
S8<


Z EVAPOTRANSPIRATION (ET) <
0 Li
-2 -
^ 7- -Z
Q; r
V> \


RATIO OF ET TO STD. PAN EVAP
RATiO OF ET TO SiT). PAN E)WP.


50 60 70 0 90 00

AGE OF PLANT, day

Fig. 2-Relationship among itea area Index (LAI), evapotransplratlon
(ET) rate, and ratio of ET to standard pan evaporation (SPE) of the
transplanted one month old seedling plans in 1980 (transplanted on
7/7 and harvested on 9/16). Each value of LAI and ET rate shows the
mean and standard deviation of three replications.


TABLE 3. RANGE AND MEAN EVAPOTRANSPIRATION
FOR WEEKLY AND THE TOTAL GROWTH PERIODS.
THE CROP SEASON AND EXPERIMENT NUMBERS ARE
CORRESPONDED TO THE NUMBERS LISTED IN TABLE 1.

Evapotranspiration
Crop Experiment Weekly period Total growth period
Crop Experiment
Season No. Range Mean Range Mean

cm/week cm
1 2.5-7.6 5.0 76.6-78.7 77.6
Spring 2 2.7-7.6 5.8 87.8-88.2 88.0
3 3.4-6.0 4.8 73.4-73.8 73.6

4 2.3-8.2 5.9 78.2-81.0 79.6
5 3.4-8.2 6.0 82.4-84.6 83.8
6 2.9-7.5 5.1 60.3-62.6 61.6
Summer 7 3.4-7.1 5.8 81.1-81.5 81.3
8 3.4-7.8 5.7 77.2-77.6 77.4
9 2.3-5.5 4.1 57.8-62.7 61.0

10 1.3-3.7 3.0 39.3-39.9 39.6
Fall 11 1.3-5.3 3.9 49.9-50.6 50.2
12 1.3-4.5 3.4 43.8-46.3 44.9


daily ET during the period of LAI estimation was
averaged from the summation of daily ET measurements
in the lysimeter. The mean daily SPE also averaged from
tme summation of daily SPE measurements in the AREC
Weather Station. The ratio of mean daily ET to the mean
daily SPE is referred as a coefficient, k_. The period for
LAI estimation was defined as a period between the half
of the interval preceding and half of the interval
following the LAI estimations. The results of LAI, ET,
and k, for the transplanted crop with 4 periods of LAI
estimation and the direct-seeded crop with 3 periods of
LAI estimation are shown in Figs. 2 and 3, respectively.


LEAF AREA INDEX


9

A
-.---. /
/


/

/ /





EVAPOTRANSPIRATION (ET)








RATIO OF ET To ST- P e
RATIO OF ET TO STD. PAN EV


35 45 55 65 75

AGE OF PLANT, day

Fig. 3-Relationship between leaf area Index (LAI),
evapotranspiration (ET) rate, and ratio of ET to standard pan
evaporation (SPE) of direct seeded plants on July 7, 1980. Each value of
LAI and ET rate shows the mean and standard deviation of three
replication.


TRANSACTIONS of the ASAE-1983


4R






Each value of LAI or ET in those two figures shows the
mean the standard deviation (S.D.) for 3 replications.
Some observations can be made from those two figures.
According to the results reported by Tomar and
O'Toole (1980), the variations of k, values for rice were in
the range of 0.7 to 1.80 which were in good agreement
with the results of the range between 1.33 and 1.84 as
shown in Fig. 2. Tomar and O'Toole (1980) reported that
the wide range variations in k, value arises because of
differences in 'crop' characterisats (aerodynamic
roughness and diffusion resistance of the canopy) and
climatic conditions. Theoretically, if the increase in ET
during the reproductive stage is attributable to climate
changes and not to the crop growth, the k, value should
be nearly constant after the crop is reaching a full canopy
condition (i.e. the LAI is greater than one). As Fig. 2
shows, the values of k, not only did not show any pattern
of constant values but also followed an increasing and
then a decreasing trend. This implies that the variation
of rice ET is not likely attributable to climate changes.
According to the study reported by Shih and Gascho
(1980), dry biomass in sugarcane was directly
proportional to the cumulative time interaction with the
LAI. In other words, the higher LAI implies greater
biomass accumulation and vice versa. Thus,
comparatively higher ET value would result due to the
large quantitiy of biomass production in accordance with
the model presented in equation [5]. As the Fig. 2 shows,
the peak ET coincided well with the maximum LAI.
Both ET and LAI changed with the growth stage
following a general pattern of steady increase starting
from the vegetative stage and reaching the maximum at
the reproductive stage, about 70 days after planting.
This implied that the rice ET steadily increased during
the vegetative stage, but rapidly decreased during the
maturity stage. This general pattern of rice ET changing
with growth is in good agreement with the results
reported by Chapman and Kininmonth (1972).
The ET, k,, and LAI values shown in Fig. 3 were only
obtained during the vegetative growth stage. The values
of k, were 0.96, 1.49, and 1.62 for the periods 1, 2, and
3, respectively. This result also showed that the k, is not a
constant value. The trend for increasing ET almost
paralleled the LAI increase.
In general, this study showed that both transplanted
and direct-seeded crops had similar patterns of ET in
relation to the physiological growth stages. The average
daily ET during the LAI estimation periods varied from 5
to 9 mm/day which was in close agreement with the rice
ET values of 4 to 9 mm/day reported by Wichkam and
Sen (1978) for Asian countries.

Evapotranspiration and Yield Relations
Dry biomass and grain yield are listed in Table 1 along
with the ratios between grain yield and dry biomass. The
ratios varied from 44 to 56% with an average of about
50%.
The dry biomass of 28 replications associated with the
total ET requirement for the entire growing season are
plotted in Fig. 4. The data were analyzed using a linear
regression as shown in equation [5] to produce
DB = 4715.2 + 303.1 ET (r' 0.94) ............. .[103

The rZ. value of 0.94 implies that the dry biomass is well
correlated to the ET value.


* LYSIMETER SITE DATA
* FIELD SITE DATA


DB -47152 + 303.1 ET
r2 0.94


II


,I I I I 1 I I ,
40 50 60 70 80 90
EVAPOTRANSPIRATION- ET, cm
Fig. 4-Several evapotranspiration requirements and dry biomass
relationships for rice.

The grain yields for 18 replications associated with the
total ET requirement for the entire growing season are
plotted in Fig. 5. The data were also analyzed using
linear regression as shown in equation [6] to produce

GY = 3995.8 + 174.9 ET (ra = 0.92). ............. .11]

The r2 value of 0.92 indicates that the rice grain yield is
also well correlated to ET.

13 r LYSIMETER SITE DATA
FIELD SITE DATA


r2 0.92


I I I i .
40 50 60 70 80 90
EVAPOTRANSPIRATION- ET, cm
Fig. 5-Several evapotranspiration requirements and grain yield
relationships for rice.


1983-TRANSACTIONS of the ASAE





The results as shown in Fig. 5 show that grain yield
varied from about 3,500 to 11,500 kg/ha. The average
grain yield harvested by growers in the EAA is about
5,500 kg/ha. The difference between the grain yields in
the small experimental site and the commercial yields
occurs mainly because of the differences in growth
environments and cultural practices. Therefore, one
practical application of this study is to rearrange the
grain yield and ET relation as shown in equation [11 for
estimating the ET requirement based on the expected
yield, i.e.

ET 22.8 + 6.7(GY/1000) .................. .[12]

For instance, if the commercial grain yield in the EAA is
expected to be 5,500 kg/ha, then the total ET
requirement will be about 54 cm for the entire growing
season.
Another practical implication of this study would be to
adjust the planting date to avoid the peak water demand
period coinciding with the dry season in the EAA.
According to these studies, the period of highest water
consumption by rice starts about 2 months after
planting. If the spring crop is planted in early March, the
critical water demand would be in May, which coincides
with the period of the highest water demand from Lake
Okeechobee. If rainfall during the wet season, which is
mainly stored in Lake Okeechobee for use in the dry
season, is below normal and rainfall during the early part
of the dry season is not in excess of normal, some water
shortage problems may arise near the end of the dry
season. Under these circumstances, delaying the
planting date might be considered so that the periods of
critical water demand does not coincide with the end of
the dry season.

CONCLUSIONS
Studies on the relationships of evapotranspiration
(ET) with grain yield, dry biomass, and leaf area index
(LAI) of rice were conducted in lysimeters and in a field
site on Pahokee muck.
Three equations involving linear leaf measurements
and stem length were developed to estimate the LAI. The
first equation estimated leaf area (A) from the length of
leaf (L) and the maximum width of leaf(W): A = 0.731
LW. The second equation estimated leaf area from leaf


length alone: A = 0.028' L2. The third equation
estimated total leaf area per stem (Y) from the stem
length (X): Y = Exp[X/(1.806 + 0.136 X + 4.478 x
10-X2)}.
The peak evapotranspiration rate coincided with the
maximum LAI value. Both ET and LAI indicated a
steady increase beginning with the vegetative stage and
reaching the maximum at the reproductive stage, then
declining during the maturity stage.
Two equations for dry biomass and grain yield as
function of ET were also developed. The relationship
between dry biomass (DB) and ET was found to be:
DB = -4715.2 + 303.1 ET. Grain yield (rough rice at
12% moisture, GY) was related to ET as:
GY = -3995.8 + 174.9 ET. These two models can be
used to improve the allocation of the amount of water
required for producing the expected rice yields. As the
average grain yield harvested by the growers in the EAA
was about 5,500 kg/ha, the total ET requirement was
approximately 54 cm for the entire growing season.

References
1. Allison, F. E., E. M. Roller and W. A. Raney. 1958.
Relationship between evapotranspiration and yields of crops grown in
lysimeters receiving natural rainfall. Agron. J. 50:506-511.
2. Alvarez, J., G. Kidder and G. H. Snyder. 1980. The economic
potential for growing rice and sugarcane in rotation in the Everglades.
Soil and Crop Science Society of Florida Proceedings 38:12-15.
3. Chapman, A. L. and W. R. Kininmonth. 1972. A water
balance model for rain-grown, lowland rice in northern Australia.
Agric. Meterol. 10:65-82.
4. Green, V. E., Jr. 1953. Rice growing is added to Everglades
Agriculture. Crops and Soils 6(1):14.
5. Hatfield, J. L., C. D. Stanley and R. E. Carlson. 1976.
Evaluation of an electronic foliometer to measure leaf area in corn and
soybean. Agron. J. 68:434-436.
6. Hillel, D. and Y. Guron. 1973. Relationship between
evapotranspiration rate and maize yield. Water Resources Research
9:743-748.
7. Shih, S. F. and G. J. Gascho. 1980. Relationship among stalk
length, leaf area. and dry biomass of sugarcane. Agron. J. 72:209-313.
8. Stephens, J. C. 1956. Subsidence of organic soils in the Florida
Everglades. Soil Sci. Soc. Amer. Proci 20:77.80.
9. Stewart. i. I., R. D. Misra, W. O. Pruitt and R. M. Hagan.
1975. Irrigation corn and sorghum with a deficient water supply.
TRANSACTIONS of the ASAE 18(2):270-280.
10. Tomar, V. S. and J. C. O'Toole. 1980. Water use in lowland
rice cultivation in Asia: A review of evapotranspiration, Agri. Water
Management 3:83-106.
11. Wickham, T. H. and C. N. Sen. 1978. Water management for
lowland rice: water requirements and yield response: In: Soils and
Rice. International Rice Research Institute. P. 649-669.


TRANSACTIONS of the ASAE-1983











Field Crops Research, 9 (1984) 315-321 315
Elsevier Science 'Palb1i'~: :r Bf.V., Anst.erdam -Printed in The Netherlands




EFFECT OF PRIOR RICE CULTURE ON SUGARCANE YIELDS IN
FLORIDA

JOSE ALVAREZ and GEORGE H. SNYDER
University of Florida, Everglades Research and Education Center, Belle Glade,
FL 33430-1101 (U.S.A.)
Florida Agricultural Experiment Station Journal Series No. 5485
(Accepted 5 July 1984)


ABSTRACT

Alvarez, J. and Snyder, G.H., 1984. Effect of prior rice culture on sugarcane yields in
Florida. Field Crops Res., 9: 315-321.

This study analyzes the effect of prior rice (Oryza sativa L.) culture upon yields of sub-
sequent sugarcane (Saccharum spp.) plant crops in south Florida. Cane crops following
rice cultivation were compared with those from nearby fields that were summer fallowed.
Information was obtained from producers' records and included geographical location,
sugarcane varieties, planting and harvesting dates, and yield data expressed as net tonnes
sugarcane per ha, percent sucrose in normal juice and tonne sugar per ha.
Ordinary least squares regression was used to derive equations to estimate what was
termed the "rice culture effect." Cane yields showed increases of 17.7 net tonnes millable
sugarcane per ha, 0.73% sucrose in normal juice, and 2 tonnes sugar per ha after rice as
compared with fallow. This increase represented $376 per ha using figures for the
1983-84 season. The results should prove useful in areas where a crop of rice can be
grown in place of a fallow.


INTRODUCTION

The value of crop rotation and multiple cropping practices is well known
to agricultural producers as a means of controlling pests and increasing in-
comes. The rice-soybean rotation in parts of the southern United States has
long been established. Louisiana is now experimenting with a rice-wheat
rotation. Although fallowing is a thing of the past for most crops, the
practice is still very common in sugarcane culture. About 100 million tonnes
of sugar are produced every year on tropical and sub-tropical lands through-
out the world. Part of that land lies idle during a few months every year,
depending on the number of ratoons obtained from each planting.
In the Everglades Agricultural Area (EAA) south of Lake Okeechobee,
Florida, about 160 000 ha of land are devoted to sugarcane production.
Sugarcane is generally harvested from November through March and


1984 Elsevier Science Publishers B.V.


0378-4290/84/$03.00













replanted from September through January approximately every 4 years.
Thus, more than 30 000 ha of land are commonly idle from 5-12 months
during the spring and summer. Producers often flood idle land as a means of
controlling insects and nematodes, and the practice may also reduce undesir-
able soil subsidence (Green 1953; Stoner and Moore 1953; Thames and Stoner
1953; Genung 1970). Recent Florida experience shows that rice can be
incorporated into the sugarcane production cycle during the fallow period
(Alvarez et al., 1978). For this reason, it is important to know the effect, if
any, of the rice culture upon yields of subsequent sugarcane crops. Such
information would help not only EAA producers but also others wherever
rice can be grown in place of a fallow period. This study was designed to
determine the effect of rice culture on yields of the following sugarcane
plant crop.

METHOD OF ANALYSIS

In the absence of data from controlled experiments in the EAA it was
possible to obtain reliable information directly from the field records of
producers. This approach is similar to the one taken by Alvarez et al. (1982)
when deriving yield prediction equations for Florida sugarcane.
Data were obtained from four firms producing rice from 1977 to 1980.
All fields have an area of approximately 16 ha and are located throughout
the EAA. The soils are all Histosols containing over 70% organic matter.
The effect of rice production on subsequent sugarcane plant crop yields
was evaluated as follows: sugarcane plant crop yield data were collected
from 82 fields in which rice immediately preceded the sugarcane crop
(termed "rice fields"). Similar data were also collected from another 36
fields located near the above fields, that were followed during the summer
prior to the next sugarcane planting ("fallow fields"). Since rice growers
generally plant on more than half their available fields, more observations
were available from "rice fields" than from "fallow fields". But, in some
instances, and due to their location in the middle of a large group of rice
fields, fewer fallow fields were necessary for comparison purposes. It was not
always possible to obtain fallow field data for the same sugarc'ane variety
that was used in the plantings that followed rice. Therefore, in addition to
the yield data (gross tonnes and percent sucrose in normal juice), informa-
tion was obtained on sugarcane variety, producing firm, planting and
harvesting dates, and method of harvesting. Thus, with an ordinary least-
squares regression, using "dummy" variables for all independent variables, it
was possible to derive equations to estimate the average sugarcane plant crop
yield for those fields in which rice production was used in place of summer
fallowing, and for those fields that were followed prior to planting sugarcane.
The difference between these yields is termed the "rice culture effect",
which is expressed as Yr Yf where Yr is the sugarcane plant crop yield in
fields previously cropped to rice, and Yf is the sugarcane plant crop yield in








0 9 9


317
fields previously fallowed. Implicit in this analysis is the assumption that
both sets of fields (which had an identical cropping sequence in the previous
cycle; i.e., fallow/sugarcane) would have produced approximately equal
sugarcane yields in the absence of rice production in one set. To check the
validity of this assumption, the plant crop data from the previous cycle in
the same fields were collected and analyzed using regression analysis.
For the purpose of the analysis, gross yields of millable sugarcane were
converted to net yields by deducting 3% trash content for hand-harvested
fields and 6% for mechanically-harvested fields. Tonnes sugar per ha were
calculated as net t ha-1 times the quality factor (which varies according to
the percent sucrose in normal juice) and times an average mill recovery
factor of 0.0882.
Multiple regression was used to assess the effect of rice culture upon the
yields of subsequent sugarcane plant crops. The following linear equation
was derived for each of the three dependent variables defined as yield
parameters to estimate the rice culture effect:
4 5 5 4
Yj=0o+Z 0liXU +02 iX2ij + 2 3iX3 +f 04iX2X X 3ij + 05iX4ij +Uj
i=1 i=1 i=1 i=1
where Yj = yield per ha from plant cane in field j, expressed as net
tonnes, percent sucrose in normal juice and tonnes of sugar;
Xi = 1 if field j was managed by firm i (i = 1,... 4),
= 0 otherwise;
Xiijj = 1 if the fallow crop was rice in field j,
= 0 otherwise;
X3A = 1 if variety i was planted in field j, and i = 1 for mixed, i = 2
for CP 63-588, i = 3 for CP 70-1133, i = 4 for CP 56-59, and
i = 5 for CL 54-378,
= o otherwise;
X2ij X X3ij = 1 if variety i was planted to rice in field j,
= otherwise;
A -, i 1 if plant cane was harvested from field j in year i, and i 1
for 1978--79, i = 2 for 1979-80, i = 3 for 1980-81 and i = 4
for 1981-82,
= 0 otherwise;
Uj random disturbance associated with field j.
In sub-tropical south Florida, freezing temperatures occur in some years
and reduce yields. The year variable was included to.account for seasonal
weather differences.

RESULTS AND DISCUSSION

The yield comparisons between the fallow fields and the rice fields for the
plant cane crop of the previous cycle supported the hypothesis that














TABLE I


Regression results of the rice culture effect qi.' .icn

Independent variable Model

Net tonnes Eustcr: Tonnes of
of cane (%) sugar


Intercept

Fir" i
1 -


2

3

4
Rice culture effect
1
0
Variety
1

2

'3

4

5
Variety x rice culture
1x1

2X1

3X'1

4X1

56X1
Season
1

2

3



n


68.15*** 11.66S***
(2.46)9 (0.38)

-30.91*** 4.36***
(9.03) (1.41)
-12.87*** 2.07***
(2.99) (0.47)
-4.66 1.80*
(6.60) (1.03)

34.00*** 1.73**
(4.82) (0.76)


1.51
(4.35)
-15.92*
(8.81)
22.16***
(4.70)
-8.69**
(4.16)


-20.54***
(6.98)
-19.99**
(9,659)
-32.79***
(6.18)
-8.13
(6.84)


1.21*
(0.68)
-2.16
(1.37)
0.05
(0.73)
0.79
(0.65)


-1.29
(1.09)
-0.60
(1.49)
--1.35
(0.96)
-1.74*
(0.99)


18.78*** -1.99*
(7.45) (1.16)
44.95"** -1.28
(6.66) (1.04)
19.80*** -1.04"*
(2.98) (0.46)

0.89 0.47
118 118


*,***** significant at the 0.10, 0.05 and 0.01 levels, respectively.
aFigures in parentheses are standard errors of the regression coefficients.


5.62"""
(0.35)

0.40
(1.30)
0.76*
(0.43)
0.97
(0.95)

4.16***
(0.69)


0.80
(0.63)
-2.85**
(1.27)
.1.74***
(0.68)
-0.38
(0.60)


-2.64***
(1.01)
-2.11
(1.38)
-3.69**"
(0.89)
"1.93**
(0.91)


-0.17
(1.07) ,
2,70***
(0.96)
0.62
(0.43)

0.79
118











319

approximately equivalent fields were chosen to estimate the rice culture
effect. No significant differences were found in the equations for percent
sucrose in normal juice (P > 0.91) and tonnes of sugar (P> 0.65). While the
net tonnes equation had a lower P value (P > 0.06), the coefficient indicated
that the fallow fields actually had higher production (5.5 net t) than the rice
fields. Thus, any positive rice effect would be conservative with respect to
net tonnes.
The regression results of the rice culture effect are shown in Table I. It is
clear that, in general, all three models are statistically sound. The coefficients
of the rice culture variable in the three models show a positive sign and high
statistical significance, indicating a beneficial effect of rice upon subsequent
yields of sugarcane. All three intercepts are significant at the 0.01 level.
There is a significant variety X rice culture interaction. The sign of the inter-
action term is the same for all varieties in the three models and only the
magnitude of the coefficients varies with variety. Therefore, a mean value
across varieties is used in all subsequent calculations. The coefficients of
determination are very good for these types of cross-section data.
TABLE II

Rice culture effect for the three models

Rice culture Model
effect
Net tonnes Sucrose Tonnes of
of cane (%) sugar

1 (Yr) 93.94 13.35 9.16
0 (Yf) 76.23 12.62 7.08
Effect 17.71 0.73 2.08

a(Yr -Y Yf), at the means of the variables.

Clearly, the rice culture effect was substantial, with increases of 17.71 in
net tonnes millable sugarcane per ha, 0.73% sucrose in normal juice per net
tonne of cane, and 2.08 tonnes sugar per ha (Table II).
Several factors related to rice culture may account for the increased sugar-
cane production. Flooding has been shown to control a variety of plant pests
such as soil borne diseases, insects and nematodes. The recycling of nutrients
by rice that might otherwise be leached from the soil by heavy summer rains
could benefit the following sugarcane crop. Improvements in soil tilth, soil
aeration, water infiltration and drainage following flooding and stubble
incorporation and better water table control associated with the use of laser
levelling may also have contributed to the higher sugarcane yields.

ECONOMIC IMPLICATIONS

There are two potential economic benefits to sugarcane growers from rice











320

production in place of fallowing. The first one is the direct return from the
rice crop to the grower and the resulting increase in employment and returns
to those servicing the industry. The second benefit derives from the returns
of the extra yield in the subsequent cane crop.
The benefit, in terms of total net returns, to subsequent sugarcane
production can be calculated using the formula:
NR = (P SRE) (HC:* GRE),
where NR equals total net returns, P equals the price per kilogram of sugar,
SRE is the rice culture effect in terms of kg ha-', HC represents the extra
harvesting, loading and hauling costs per gross tonne of cane, and GRE is the
rice culture effect in terms of gross t ha-.
The rice culture effect was 2,08 t of sugar (Table II). Harvesting, loading
and hauling costs for the 1983-84 season were $11 per gross tonne of cane.
The average season price is estimated to be around $0.44 per kg New York
spot price, with $0.277 going to the grower as shown by Halsey (1976). In
terms of gross tonnes, the rice culture effect was 18.24 assuming a 3% trash
content. Therefore, the rice culture effect amounted to a net return of $376
per ha. Extra returns also accrue to processors grinding that cane and to both
growers and processors from the additional molasses produced.

TABLE III

Sugarcane production and recovered sugar statistics, Florida, 1958-82, at 4-year intervals

Year Production Recovered sugar
(t ha-') (%)
1958 84.78 10.45
1962 79.39 9.39
1966 71.14 10.77
1970 74.73 11.49
1974 62.27 11.20
1978 75.71 10.60
1982 76.16 10.10

Source: Agricultural Stabilization and Conservation Service; Economic Research Service;
Economics and Statistics Service.

Table III shows that both net tonnes of cane per ha and percent of re-
covered sugar have remained fairly constant for Florida during the past quarter
century. Furthermore, as sugarcane production expands to areas of poorer
soils, yields are unlikely to increase in the next few years. However, an
average 23% increase in net tonnes can be obtained by simply growing rice
before replanting sugarcane fields. The actual magnitude of the "rice culture
effect" for individual producers will, of course, vary with variety (Table I),
and will be affected by soil conditions existing prior to the rice crop.















CONCLUSION

The cultivation of rice on land that would otherwise be followed in the
EAA had a positive effect on the subsequent yield of the sugarcane plant
crop. This effect could be of major economic importance to the sugarcane
industry in south Florida and possibly in other areas of the world where rice
can be grown in rotation with sugarcane.


REFERENCES

Agricultural Stabilization and Conservation Service, 1970. Sugar Reports, No. 220,
USDA, Washington, DC, pp. 34-35.
Agricultural Stabilization and Conservation Service, 1971. Sugar Reports, No. 231,
USDA, Washington, DC, pp. 25-26.
Alvarez, J., Kidder, G. and Snyder, G.H., 1978. The economic potential for growing rice
and sugarcane in rotation in the Everglades. Soil Crop Sci. Soc. Florida Proc., 38:
12-15.
Alvarez, J., Crane, D.R., Spreen, T.H. and Kidder, G., 1982. A yield prediction model for
Florida sugarcane, Agric. Syst., 9: 161-179.
Economic Research Service, 1976. Sugar and Sweetener Report, Vol. 1, No. 11, USDA,
Washington, DC, p. 9.
Economic Research Service, 1982. Sugar and Sweetener Outlook and Situation, No.
SSRV7N3, USDA, Washington, DC, p. 17.
Economics and Statistics Service, 1981. Sugar and Sweetener Outlook and Situation,
No. SSRV6N1, USDA, Washington, DC, pp. 28-29.
Genung, W.G., 1970. Flooding experiments for control of wireworms attacking vegetable
crops in the Everglades. Fla. Entomol., 53: 55-63.
Green, V.E., Jr., 1953. Rice growing is added to Everglades agriculture. Crops Soils, 6:
14.
Halsey, L.A., 1976. A management guide to profitable sugar production, AREC Research
Report EV-1976-8, University of Florida, Gainesville, FL, 10 pp.
Stoner, W.N. and Moore, W.D., 1953. Lowland rice farming, a possible control for
Sclerotinia sclerotiorum in the Everglades. Plant Dis. Rep., 37: 181-186.
Thames, W.H., Jr. and Stoner, W.N., 1953. A preliminary trial of lowland rice culture in
rotation with vegetable crops as a means of reducing root-knot nematode infestations
in the Everglades. Plant Dis. Rep., 37: 187-192.












Reprinted from The Florida Entomologist, Volume 69, Number (1), March 1986.

LEAFHOPPERS (HOMOPTERA: CICADELLIDAE) AND
PLANTHOPPERS (HOMOPTERA: DELPHACIDAE) IN
SOUTHERN FLORIDA RICE FIELDS

R. H. CHERRY AND D. B. JONES
University of Florida, IFAS
Everglades Research and Education Center
P. 0. Drawer A
Belle Glade, Florida 33430
AND
F. W. MEAD
Florida Dept. Agric. and Consumer Services
Division of Plant Industry
P. 0. Box 1269
Gainesville, Florida 32602

ABSTRACT
Leafhoppers (Homoptera: Cicadellidae) and planthoppers (Homoptera: Delphacidae)
were collected with sweep nets in southern Florida rice fields during 1983 and 1984.
The most abundant leafhopper was Graminella nigrifrons (Forbes) and the most abun-
dant planthopper was Delphacodes propinqua (Fieber). Total numbers of leafhoppers
in rice fields rose quickly after spring plantings and remained relatively constant from
May to October. In contrast, individual leafhopper species were more variable in sea-
sonal population trends. Sogatodes oryzicola (Muir), a vector of hoja blanca was also
detected.

RESUME
Salta hojas (Homoptera: Cicadellidae) y salta plants (Homoptera: Delphacidae) se
recogieron con Jabecas en campos arroceros del sur de la Florida durante 1983 y 1984.
Se discuten las distintas species de importancia ec6nomica que se encontraron. El salta
hojas mAs abundante fue el Graminella nigrifrons (Forbes) y el salta plants mAs abun-
dante fue el Delphacodes propinqua (Fieber). El nimero total de salta hojas en los
compos arroceros aument6 rapidamente despfies de las siembras de primavera, man-
tenfendos relativamente constant de Mayo a Octubre. Sin embargo, las poblaciones de
algunas species de salta hojas mostraron cambios estacionales dramaticos. Tambidn se
decect6 a Sogatodes orizicola (Muir), un vector dela hoja blanca.


Rice was grown for grain in the Everglades agricultural area of southern Florida
during the 1950's. Commercial production was stopped in 1957 by the United States
Federal Government after the hoja blanca (white leaf) disease was found in the area.
The lifting of controls on production by the Federal Government in 1974 made it possible
again to harvest Florida rice for grain (Alvarez 1978). Since 1977 rice production in the
area has grown to nearly 4,000 ha and drying and milling facilities have been established
(Rohrmann & Alvarez 1984). Currently, ca. 85% of Florida rice is grown in the
Everglades agricultural area.
Several species of leafhoppers and planthoppers are serious pests of rice in different
areas of the world and frequently occur in numbers large enough to cause complete
drying of the crops. In addition to the damage resulting from direct feeding, leafhoppers
and planthoppers are vectors of most presently known rice virus diseases (Pathak 1968).
Other than a brief description of leafhoppers and planthoppers in Everglades rice fields













Cherry et al.: Rice Leqfhoppers 181
by Genung et al. (1979), little is known of the species composition or seasonal population
dynamics of leafhoppers and planthoppers occurring in Florida rice. In this study, we
describe the relative abundance of leafhoppers (Cicadellidae) and planthoppers (De-
lphacidae) occurring in southern Florida rice fields.

MATERIALS AND METHODS
Eight commercial rice fields in the Everglades agricultural area of southern Florida
were sampled with 38.1-cm-diameter sweep nets each year during the 1983 and 1984
growing seasons. During much of the growing season, these rice fields were kept flooded
and were underlain with soft muck. Sweep nets were thus used because they are light
and portable. Southwood (1978) discusses advantages and limitations of sweep net sam-
pling for insects. Each field was ca. 16 ha and fields were located throughout the
Everglades agricultural area to obtain a representative sample of insect populations.
All fields were subject to normal rice production practices including planting dates that
ranged from March 1 through May 12. Each field was sampled weekly by making 100
consecutive sweeps (180) taken about 50 meters into the field to avoid possible edge
effects. Sweeping began 6 weeks after planting and continued through harvest. Eight
fields were removed from production after one harvest during August to September
and eight fields were removed from production after one ratoon crop during October to
November. After collection, insects were frozen for later counting. Only adults of the
leafhoppers and planthoppers were counted because of the large number of insects
collected and to facilitate taxonomic identification. An overall survey of the relative
abundance of the leafhopper and planthopper species was determined from 42 random
samples containing 6060 leafhoppers and planthoppers identified by F. W. Mead. There-
after, the seasonal abundance of the total number of leafhoppers and 3 most abundant
leafhopper species was determined. These latter 3 species were ca. 97% of all leafhop-
pers collected. Delphacid seasonal abundance was not determined because of the low
numbers of these insects collected.

RESULTS AND DISCUSSION
The relative abundance of leafhoppers and planthoppers in sweep net samples in
Florida rice fields is shown in Table 1. Leafhoppers outnumbered planthoppers ca. 41 to
1. Genung et al. (1979) also reported that leafhoppers were more abundant on
Everglades rice than planthoppers. Generally, leafhoppers feed on the leaves and upper
parts of rice plants, whereas planthoppers confine themselves to the basal parts (Pathek
1968). Thus, our sweep net samples probably overestimated leafhoppers relative to
planthoppers present in the rice. The most abundant leafhopper was the blackfaced
leafhopper, Graminella nigrifrons (Forbes). This species has a wide distribution on
grasses in the eastern United States and breeds on rice (Stoner & Gustin 1967). This
species is also a vector of several corn stunting pathogens (Nault & Bradfute 1979). The
second most abundant leafhopper was Draeculacephala portola Ball which is the most
common Draculacephala in eastern and central United States and has been reported
in Cuban rice fields (Young & Davidson 1959). Since this insect is common on sugarcane
in the southern United States (Pemberton & Charpentier 1969) and is a recognized
sugarcane pest in Florida (Strayer 1975), some D. portola probably immigrated into the
rice fields from the numerous sugarcane fields in the Everglades area. Abbott & Ingram
(1942) reported the transmission of chlorotic streak of sugarcane by D. portola but,
Pemberton & Charpentier (1969) thought that the insect transmission of chlorotic streak
had not been adequately demonstrated in light of more recent studies. The most abun-
dant planthopper was Delphacodes propinqua (Fieber) which is also a vector of maize












182 Florida Entomologist 69(1) March, 1986
TABLE 1. RELATIVE ABUNDANCE' OF LEAFHOPPERS AND PLANTHOPPERS IN
FLORIDA RICE FIELDS.

Cicadellidae Number % of Total

Graminella nigrfrons (Forbes) 3891 65.8
Draeculacephala portola Ball 988 16.7
Balclutha incisa (Matsumara) 884 14.9
Draemulacephala product (Walker) 51 0.9
Balclutha hebe Krkaldy 40 0.7
Other species2 61 1.0

5915 100.0
Delphac!dae Number % of Total

Delphacodea propinqua (Fieber) 79 54.5
Perkinsiella saecharicida Kirkaldy 20 13.8
Saccharosydne saccharivora (Westwood) 12 8.3
Sogatella kolophon (Bmr.) 12 8.3
Sogatodes molinus Fennah 12 8.3
Other species' 10 6.9

145 100.1

Based on random samples identified by F. W. Mead (see text).
lB, ujaenae (DeLong), Eitianus exitiosus (Uhler), Hcrtensia similis (Walker), Marro.lele fhsrifle ns (Stal),
PlanieCphhahe flavicosta (Stal).
Delpharodes p-ella (Van Duzee), Pissonotus piceus Van Duzee, Sogatodes orizirola (Muir).

rough dwarf virus (Break 1979). The second most abundant planthopper was the sugar-
cane delphacid, Perkinsiella saccharicida Kirkaldy. This species is a serious sugarcane
pest of Australian origin. Besides direct damage to sugarcane by feeding and oviposi-
tional activities, the insect is also a vector of the virus that causes Fiji disease in
sugarcane. The first North American record of P. saccharicida was reported in 1982 in
Palm Beach County, Florida. Subsequent surveys revealed the delphacid throughout
southern Florida (Sosa 1983). Another delphacid detected in this study is Sogatodes
oryzicola (Muir). This insect is a vector of hoja blanca which is one of the most destruc-
tive rice diseases in the Western Hemisphere (Harris 1979). Fortunately, hoja blanca
currently is not known to exist in the United States. Detection of S. oryzicola in this
study is the first report of the insect in the United States in more than a decade.
The seasonal population trends of leafhoppers in the sweep net samples are shown
in Fig. 1. Total numbers of leafhoppers rose quickly in April and remained relatively
constant (Range = 44 to 78 adults/100 sweeps) from May until October, decreasing to
26 adults!100 sweeps in November. In contrast to the total leafhopper numbers, the 3
most abundant leafhopper species showed more variable seasonal trends. The early
increase of leafhoppers in rice fields during April and May was almost wholly (> 97%)
due to G. nigrifrons. During June to August, G. nigrifrons remained> 75% of all
leafhoppers, and then declined to lower levels during September to November. Genung
& Mead (1969) also found a decline in G. nigrifrons populations after August in pasture
grasses in southern Florida. D. portola populations increased slowly during April to
June and remained somewhat constant (Range = 8 to 23 adults/100 sweeps) thereafter.
In contrast to G. nigrifrons or D. portola, Balclutha incisa (Matsumara) increased
rapidly during the late summer to fall period and during October was the most abundant
leafhopper species. Reasons for this October increase in B. incisa are not known, but













Cherry et al.: Rice Leafhoppers


Total------
G. nigrifrons -
D. portola---- ---
8. Incis----


K\ ^ X


I \- ^- \



/ \
t\ -


April May June July


Aug Sept Oct


Fig. 1. Mean adult leafhoppers per 100 sweeps in eight Florida rice fields sampled
each year during 1983 and 1984. Each field was sampled weekly with 100 continuous
1800 sweeps with a 38.1 cm diameter sweep net. Fields were located throughout the
Everglades agricultural area of southern Florida.

may be related to the weedy condition of a few of the ratooned rice fields.
In conclusion, Genung et al. (1979) have noted that leafhoppers are often very abun-
dant on southern Florida rice and may contribute to the unthrifty appearance and
discoloration often observed in the rice. Currently, southern Florida rice growers have
expressed no concern for leafhopper or planthopper populations in their rice fields and
S. orizicola was the only rice disease vector detected in our survey. However, several
economically important leafhopper and planthopper species including potential disease
vectors are present in the fields and may increase rapidly in numbers. Presently, we
have little understanding of the impact of leafhoppers and planthoppers on southern
Florida rice production or how these insects are interacting with other local crops such
as corn and sugarcane. These above subjects warrant future research, especially if rice
acreage continues to increase in southern Florida.

ACKNOWLEDGMENTS

We express our gratitude to the numerous rice growers who allowed us use of their
fields and Dr. J. P. Kramer for help in identifying some specimens and Dr. J. Alvarez
for the Spanish translation. This is Agricultural Experiment Station Journal Series No.
6376 and FDACS, DPI, Bur. Entomology Contribution No. 610.

REFERENCES CITED

ABBoTT, E. V., AND J. W. INGRAM. 1942. Transmission of chlorotic streak of sugar


100 -



80-
So-



g 60

0

. 40-
0

20-
20-


/-N


_ I I __ ~ t












Florida Entomologist 69(1)


cane by the leaf hopper Draecduacephala portola. Phytopathology 32: 99-100.
ALVAREZ, J. 1978. Potential for commercial rice production in the Everglades.
Economic Information Report 98. Food and Resource Economics Dept., Univ.
of Florida.
BRCAK, J. 1979. Leafhopper and planthopper vectors of plant disease agents in central
and southern Europe, pp. 97-155. In Maramorosch, K., and K. Harris (eds.),
Leafhopper vectors and plant disease agents. Academic Press, New York.
GENUNG, W. G., AND F. W. MEAD. 1969. Leafhopper populations (Homoptera:
Cicadellidae) on five pasture grasses in the Florida Everglades. Florida Ent. 52:
165-170.
GENUNG, W. G., G. H. SNYDER, AND V. E. GREEN, JR. 1979. Rice-field insects in
the Everglades. Belle Glade AREC Research Rept. EV-1979-7.
HARRIS, K. F. 1979. Leafhoppers and aphids.as biological vectors: vector-virus re-
lationships, pp. 217-309. In Maramorosch, K., and K. Harris (eds.), Leafhopper
vectors and plant disease agents. Academic Press, New York.
NAULT, L. R., AND 0. E. BRADFUTE. 1979. Corn stunt: involvement of a complex
of leafhopper-borne pathogens, pp. 561-587. Ibid.
PATHAK, M. D. 1968. Ecology of common insect pests of rice. Ann. Rev. Ent. 13:
257-294.
PEMERTON, C. E., AND L. E. CHARPENTIER. 1969. Insect vectors of sugar cane
virus diseases, pp. 411-427. InJ. R. Williams, J. R. Metcalfe, R. W. Mungomery,
and R. Mathes (eds.), Pests of sugar cane. Elsevier, New York.
ROHRMANN, F., AND J. ALVAREZ. 1984. Costs and returns for rice production on
muck soils in Florida, 1984. Economic Information Report 202. Food and Re-
source Economics Dept., Univ. of Florida.
SOSA, 0., JR. 1983. Sugarcane delphacid discovered in Florida. Sugar J. 45: 16.
SOuTHwooD, T. R. 1978. Ecological methods with particular reference to the study
of insect populations. Second Edition. Chapman and Hall, New York.
STONER, W. N., AND R. D. GUSTIN. 1967. Biology of Graminella nigrifrons
(Homoptera: Cicadellidae), a vector of corn (maize) stunt virus. Ann. Entomol.
Soc. America 60: 496-505.
STRAYER, J. 1975. Sugarcane insect control. Florida Coop. Ext. Serv. Entomol. Rept.
40.
YOUNG, D. A., JR., AND R. H. DAVIDSON. 1959. A review of leafhoppers of the
genus Draeculacephala. USDA Tech. Bull. 1198.


March, 1986








Silicon Fertilization of Rice on Everglades Histosols'

G. H. SNYDER, D. B. JONES, AND G. J. GASCHO2


ABSTRACT
Rice (Oryra sativa L), one of the world's most widely grown grain
crops, is seldom grown on Histosols, in part because of many prob-
lems related to plant nutrition. Studies were conducted on Terra Ceia
muck (Typic Medisaprists) in the Evergades to determine the effect
of calcium silicate slag on 'Lebonnet' rice production. Grain yields
were increased in excess of 30% in each of 3 yr by preplant appli-
cation of slag at 10 Mg ha- or more. Rice in plots receiving slag
had greater height, greater number of paaicles per square metcr,
heavier grains, and less dfi ,-3... AMi'- ',; tie slag contained a num--
ber of plsat nutrients, Si appeared to be the factor mest responsible
for the observed results. A positive linear relationship was observed
in all years between straw Si and grain yield. First crop straw av-
eraged 1.3, 5.0, and 5.9 dag Si kg' In plots receiving 0, 10, and 20
Mg slng ha-', respectively. A first crop straw Si concentration <3.0
dag SI kg-' was associated with reduced rice yield. Perhaps Si ap-
plicateon should be considered in other regions when difficulties are
encountered with rice production n Histosols.
Addtiod l Index Words: Orya sativa L, slag, organic sols, Hel-
mrnthosporium oryacae B. de ilaan.
Snyder, G.H., D.S. Jones, and G.J. Gascho. 1986. Silicon fertiliz-
ation of rice on Everglades Histosos. Soil Sci. Soc. A J. 50:1259-
1263.


HISTOSOLS WITH ORGANIC MATTER contents in ex-
cess of 80% (m m-') are being utilized for rice
(Oryza sativa L.) production in the Everglades. While
rice is not produced on Histosols elsewhere in the USA,
Histosols are used for rice production on a limited
basis in other countries: Indonesia, Malaysia, Sri
Lanka, Japan, Italy, Czechoslovakia, Jamaica, and
several African and South American countries (11).
There are approximately 32 million ha of Histosols in
the tropics, constituting one of the last untapped world
soil reserves (4, 5, 15). Although it seems logical to
S use these wetland sites for semi-aquatic crops such as
rice, many problems related to improper plant nutri-
tion have been documented (11). The International
Rice Research Institute (IRRI) has conducted special
projects on "adverse soils," a term that includes His-
tosols (13, 14). Rice production problems in the Ev-
erglades include less than satisfactory yield, above av-
erage sterility, lodging, and severe infestation by
Helminthosporium oryzae B. de Haan.
Many Histosols in the Everglades contain I to 2 dag
total Si kg"' (% Si), or less (2, 8), whereas total Si in
a list of 12 reference mineral soils from the south-
eastern USA ranged from 20 to 44 dag kg-' (17). Fur-
thermore, the bulk density of Histosols may be only
20% that of mineral soils. Hence, there is much less
Si in the rootzone of plants growing in Everglades His-
tosols than in most mineral soils. Water-soluble Si in

Contribution from the Univ. of Florida Institute of Food and
Agricultural Sciences. Agricultural Experiment Station Journal Se-
ries no. 6972. Received 9 Dec. 1985.
2 Professor and Assistant Professor Everglades Research and Ed-
ucation Center, P.O. Drawer A, Belie Glade, FL 33430, and Pro-
fessor, Soil Science Dep., Univ. of Georgia, Coastal Plains Experi-
ment Station, Tifton, GA, respectively.


highly organic soils of the Everglades has been re-
ported (9) to range from 0 to 95 mg kg-' (mean of 25
ng, air-dry soil basis). Sugarcane (Saccharum spp. L.)
yields on Everglades Histosols were significantly in-
creased by applications of calcium silicate slag, a ma-
terial that contained approximately 20 dag Si kg-' (8).
The importance of silica in rice production has been
extensively reviewed (6). Rice absorbs large amounts
of Si. Takijima and Gunawardena (23) have reported
that, when yields are satisfactory, straw of japonica
and indica cultivars contain > 5.0 and 3.8 dag Si kg-',
respectively. Even though the essentiality of Si is ques-
tionable, Si has been reported to benefit rice in a num-
ber of ways (6): (i) improvement in efficiency of sun-
light use and increase in photosynthetic activity, (ii)
reduction in transpiration and improvement in water
use efficiency, (iii) increased mechanical strength of
cells and reduction in lodging, (iv) increased resistance
to certain insects and diseases, (v) reduction in ac-
cumulation of toxic concentrations of Mn and other
heavy metals, (vi) improvement in rice plant nutri-
tion, (vii) reduction in seed shattering, (viii) more erect
leaves, (ix) increased tillering, (x) improved P metab-
olism, and (xi) increased shoot height, number of
spikelets per ear, 1000-grain weight, and percentage of
filled spikelets.
A number of Si sources have been used as silicate
fertilizers (6): furnace slags obtained by melting Fe
ore, wollastonite, dolomite slags, calcium metasilicate
slags that are by-products of production of P in electric
furnaces, sodium metasilicate, and cement. Because
these materials contain a variety of elements, includ-
ing plant nutrients, in addition to Si, there always is
some question whether or not observed responses are
solely due to Si. Application of most slag materials
also increases soil pH.
Reports of nutritional disorders of rice grown on
Histosols have focused on N, S, K, Fe, Cu, Mn, Zn,
and various soluble organic compounds (11, 13). Al-
though Histosols, almost by definition, contain rela-
tively little Si, the authors are unaware of any pub-
lished reports specifically dealing with the Si nutrition
of rice grown on Histosols. Because of interest in Flor-
ida and elsewhere in rice production on Histosols, pre-
vious observations of positive sugarcane responses to
Si applications in the Everglades, and evidence of the
importance of Si to high rice yields in other regions,
studies were undertaken to determine whether Si ad-
ditions would improve rice yields on Histosols in the
Everglades.
METHODS AND MATERIALS
Experiments were conducted at three different locations
in the northeastern Everglades during the years 1981 to 1983.
In all years the soil was a Terra Ceia muck (Euic hyper-
thermic Typic Medisaprists), a Histosol >130 cm in depth
over limestone. This soil series alone accounts for about40%
of the cultivated Everglades (19). In all studies an electric
furnace calcium silicate slag produced as a by-product of
elemental P production in Florida was soil incorporated prior
to seeding (Table 1). Silicon in the slag was determined by
1259






SOIL SCI. SOC. AM. J., VOL. 50. 1986


Table 1. Chemical analysis of calcium silicate slag
used in the studies.
P K Ca Mg Si Fe Mn Zn Cu
dag kg----- mg kg- --
0.6 0.1 33.0 0.3 22.0 0.5 190 12 15


Table 2. Soil pH, water extractable P, 0.5 M HOAc extractable
K, Ca, and Mg, and total Si in soils used in the 3 study yr.
Study year pH P K Ca Mg Si
kg ha- dag kg"-
1981 4.9 22 191 1834 245 0.98
1982 5.1 4 24 2074 211 0.81
1983 6.6 1 73 5618 565 0.70
Recommendation
for rice 122) 6 112 -

the blue silicomolybdous acid procedure (12). The same pro-
cedure was used to determine total soil Si. Other elements
in the slag were determined in an HCI digest by routine
analytical procedures, after removing Si with HF; the diges-
tion and Si removal being conducted in teflon beakers.
The cultivar Lebonnet was used in all studies. Seeds were
drilled at a depth of ca. 3 cm and a row spacing of 17.5 cm.
The seeding rate was ca. 100 kg ha '. Ferrous sulfate at a
rate of ca. 100 kg ha-' was drilled with the seed. The fer-
tilizer nutrients P, K, Zn, and B were applied preplant ac-
cording to soil test recommendation (22). Fields were flooded
3 to 6 weeks after seeding, and the flood was continuously
maintained until about 2 weeks before the first harvest. The
fields were reflooded after harvest in the first and third years
and the rice was allowed to regrow for a ratoon crop. The
floodwater was removed approximately 2 weeks prior to
harvest of the ratoon crop.

1981 Study
Nine 3- by 21-m plots were located at random in a com-
mercial rice field prior to planting. Calcium silicate slag at
10 Mg ha-' was applied to a 7-m strip at one end (randomly
chosen) of each plot. The 7-m strip at the other end of the
plot served as the check, and the 7-m strip separating the
above two subplots served as a border area. The slag was
rototilled to an approximate depth of 15 cm and the plot
was rolled to firm the soil. The commercial grower seeded
the nine plots at the same time as the rest of the field, and
maintained the field according to the standard commercial
practices summarized above. No fertilizer was applied be-
cause soil test levels were above the critical levels for rice
(Table 2). The slag was applied on 6 May and seeding was
completed on 11 May. At panicle initiation (9 July) Y-leaves
(the most recent fully mature leaf) were sampled (40
subplot-'). The rice grain was harvested on 3 September by
hand cutting 4 m of two rows from the center of each sub-
plot. Data were taken on the weight of harvested grain, on
the number of heads per sampled area paniclee density), and
on the weight of 100 grains. All grain yields were adjusted
to a moisture content of 12 dag kg-' and are reported as
unhulled grain (i.e., "rough-rice"). The yield components
panicle weight and grains per panicle were calculated from
the yield, panicle density, and grain weight data. The average
distance from the ground to the base of the flag leaves was
recorded for each subplot. The ratoon crop was harvested
in a similar manner on 4 December.
Silicon in plant tissue was determined by slightly modi-
fying an established gravimetric procedure (26). Tissue sam-
ples weighing 0.3 g were wet acid digested (18). Two to three
digestates were filtered through ashless paper. The residue
was washed with dilute HCI. The filter paper containing the
Si residue was ignited and ashed in a muffle furnace at 550C


Table 3. Effect of calcium silicate slag on rice grain yield.
First crop Ratoon crop
Amendment Rate 1981 1982 1983 1981 1983
Mg ha-'
Slag 0 3.4 5.3 4.3 1.7 2.9
2.5 6.3 -
5.0 6.6 6.3 -- 3.9
10.0 4.6 7.2 2.0 -
20.0 7.7 6.9 4.4
Treatment effects
Linear ** ** ** ** **
Quadratic -
*.** Statistical significance at P <0.05 and 0.01. respectively.
in preweighed Ni crucibles. The residue, assumed to be SiO2
("crude silica"), was weighed and Si was calculated as de-
cagram per kilogram tissue. Nitrogen and P were determined
in separate 0.3-g tissue digestates by automated colorimetery
(Technicon Industrial Systems Method no. 334-74 W/B,
Technicon Instruments Corp., Tarrytown, NY), and metal-
lic elements were determined by atomic absorption spectro-
photometry. Data were subjected to analysis of variance and
regression analysis by SAS (20) techniques, where appro-
priate.

1982 Study
Calcium silicate slag was incorporated into plots 3 by 10
m at rates of 0, 2.5, 5, 10, and 20 Mg ha prior to planting
of a commercial rice field. There were three additional treat-
ments: (i) aragonitee" limestone (CaCO. mined in the Ba-
hama Islands) at 16 Mg ha ', (ii) iron sulfate (heptahydrate)
at 0.5 Mg ha ', and (iii) triple superphosphate at 1.0 Mg
ha '. These treatments were designed to supply Ca, Fe, and
P, respectively, at rates supplied by the highest rate of slag.
The study was arranged as a randomized complete block
design with five replications. Prior to seeding, all plots ex-
cept Treatment iii, above, were fertilized with P at 9 kg ha-'
and with K at 140 kg ha '. The rice was seeded on 19 March
and four center rows of each plot were harvested as de-
scribed above on 16 July. Plant height at harvest was mea-
sured at the panicle neck. About 3 weeks before harvest (25
June 1982), a visual rating was made of discolored florets,
expressed as a percentage of total florets. Soil pH was mea-
sured in samples (0-10 cm) taken 14 April, prior to flooding.
Plant tissue was analyzed as previously described. Because
of severe crop damage by sheath blight (Rhizoctonia solani
Kuhn) throughout the commercial field, ratoon data were
not obtained.

1983 Study
Slag was incorporated into plots 2 by 10 m at rates of 0,
5, and 20 kg Mg prior to planting of a commercial rice
field. There were eight replications in a randomized com-
plete block design. The field was fertilized with the following
nutrients at the indicated rates (kg ha -'): P-19, K-138, Mn-
6, Zn-6, and B-I. The rice was planted 25 April and combine
harvested on 25 August. The day before harvesting, 20 flag
leaves were removed from the check and 20 Mg ha-' plots
to evaluate infection by Helminthosporium oryzae. Lesions
counted on I-cm2 sections of each of the 20 leaves plot-'
were averaged by plot. The area of the flag leaves was esti-
mated from measurements of length and width (21). The
ratoon crop was harvested on 15 November. Plant height at
time of first crop harvest was measured to the extended pan-
icle tip. Plant tissue was analyzed as described above.

RESULTS AND DISCUSSION
Rough-rice yields were significantly increased in all
crops by application of calcium silicate slag (Table 3).


1260







SNYDER ET AL.: SILICON FERTILIZATION OF RICE ON EVERGLADES HISTOSOLS


Table 4. Effect of calcium silicate slag on rice plant height and yield components.
First crop Ratoon crop
Slag Plant Panicle Panicle Grains 1000- Plant Panicle Panicle Grains 1000-
Year rate height mrn wt panicle- grain wt height m"n wt pancle-' grain wt
Mg ha"' cm no. g no. g cm no. g no. g
1981 0 73 296 1.7 68 25 61 466 0.56 25 23
10 88 372 1.8 68 26 64 548 0.58 25 24
Significance ** ** NS NS NS ** t NS t
1982 0 96 298 1.8 75 24 -
2.5 101 288 2.2 89 25 -
5.0 100 315 2.1 85 25 -
10.0 101 348 2.1 83 25 -
20.0 103 338 2.3 92 25 -
Treatment effects
Linear ** NS NS *
Quadratic NS t NS NS t
1983 0 91 -
5.0 103 ----
20.0 111 .- -
Treatment effects
Linear *
Quadratic **
**,.t Statistical significance at P <0.05, 0.01, and 0.10, respectively.


The 10 Mg ha-' rate of slag increased grain yield by
33 and 35%, relative to the check, in 1981 and 1982,
respectively. The 20 Mg ha-' rate increased yield by
44 and 58% in 1982 and 1983, respectively. Ratoon
crop yields also were significantly affected by appli-
cation of slag prior to seeding the first crop. The 10
Mg ha-' rate in 1981 increased ratoon crop yield by
20%, relative to the check, and the 20 Mg ha-' rate
in 1983 increased ratoon yield by 53%. Using a quad-
ratic response model, rice yields in 1982 and 1983
were related to slag application rates as
1982 first crop yield = 5480 + 257.0 X slag 7.4
X slag2
model R2 0.78
1983 first crop yield = 4390 + 481.8 X slag 17.8
X slag2
model R2 = 0.91
1983 ratoon crop yield = 2887 + 232.5 X slag 7.8
X slag2
model R2 = 0.93,
where yield is expressed as kg ha-' and slag rates as
Mg ha-'. The linear and quadratic coefficients for slag
were significant for all models (Table 3). Using these
equations, the slag rates corresponding to maximum
first crop yield in 1982 and 1983 were 17.4 and 13.5
Mg ha-', respectively. Maximum ratoon crop yield in
1983 was calculated at a slag rate of 14.9 Mg ha-1.
Calcium silicate slag increased plant height in the
first crop, but not in the ratoon, and increased panicle
number in both crops (Table 4). Grain weight also was
significantly (P <0.10) increased in plant and ratoon
crops. Soil pH, prior to flooding, was 5.1, 5.4, 5.4, 5.6,
6.0, and 6.3 in plots receiving slag at 0, 2.5, 5, 10, and
20 Mg ha-' and in limed plots, respectively.
A few additional observations were made on the
effect of slag application during the 3-yr study period.
Rice in slag treated plots matured 4 to 7 d later than
in check plots (data not shown). In 1981, lodging was


Table 5. Effect of calcium silicate slag on silicon content
of rice straw.
Year Slag First crop Ratoon crop
Mg ha" dag kg-' -
1981 0 1.6 3.4
10 4.5 5.6
Significance ** **
1982 0 0.9
2.5 2.5 -
5.0 3.8
10.0 5.5
20.0 5.5
Treatment effects
Linear **
Quadratic **
1983 0 1.5 2.6
5.0 4.3 3.7
20.0 6.3 4.9
Treatment effects
Linear ** **
Quadratic ** **
*,** Statistical significance at P <0.05 and 0.01, respectively.


observed in three of the nine slag-treated plots, but
not in check plots. No lodging was observed in other
years. One of the most obvious visible effects of slag
application in all years was reduced floret discolora-
tion in treated areas relative to the check plots and
the commercial rice in the remainder of the field. Slag
plots could easily be distinguished from a distance of
50 m or more at time of harvest. In the rating for floret
discoloration conducted in 1982, check plots averaged
58%, and the 2.5 Mg slag ha-' treatment averaged
25%. Plots receiving higher slag rates had 11% or less
discolored florets (LSDo.s =- 15). In 1983, H. oryzae
lesion counts on flag leaves averaged 72 and 28 cm-2
in check and 20 Mg ha-' plots, respectively (means
significantly different at P <0.01). Flag leaves aver-
aged 44 and 52 cm2 leaf- in area for check and treated
plots, respectively (means significantly different at P
<0.01).


1261





SOIL SC. SOC. AM. J., VOL. 50, L986


Clearly, calcium silicate slag application greatly in-
creased rice production. However, since the slag con-
tained a number of plant nutrients (Table 1), the rea-
son for the increase must be carefully assessed. Silicon
in straw was significantly related to slag application in
all years (Table 5). Straw (first crop) from untreated
plots contained from 0.9 to 1.6 dag Si kg-', whereas
a Si content of 3.8 dag kg-' has been established by
some workers as minimal for satisfactory yields of in-
dica varieties, such as Lebonnet (23). Straw Si equaled
or exceeded this value for slag applications of 5 Mg
ha-' or greater. Highly significant (P <0.01) linear
positive relationships between straw Si and grain yield
were found in all 3 yr (1981 R2 = 0.71, 1982 R2 =
0.80, 1983 R2 = 0.84). In 1983, an even better fit was
obtained using a quadratic model (R2 = 0.90). Coef-
ficients for both linear and quadratic Si terms were
highly significant (P <0.01). Applying the Cate-Nel-
son partitioning technique (3) to grain yields for the
3 yr, expressed as a percentage of the highest yield in
each year, a critical Si level of 3.0 dag kg-' was ob-
tained for straw (Fig. 1).
Slag also significantly affected Y-leaf and straw el-
emental content for certain other nutrients (Table 6),
but changes were not as marked as those for Si. Ni-
trogen, Ca, and Mg decreased in first crop tissue with
increasing rates of slag, perhaps as a result of dilution
by the taller growing rice plants. The micronutrients
Fe, Mn, and Zn either were not affected by slag ap-'
plication or decreased in plant tissue with increasing
rates of slag. Dilution and increased soil pH as a result
of slag application may account for the latter obser-
vation. Nitrogen, P, Fe, Mn, and Zn in leaf tissue, and
K, Ca, and Mg in straw generally exceeded published
critical concentrations (25), regardless of treatment.
The Cu content of straw was lower than a frequently
cited (24) value (<6 mg kg-'). However, examination
of the source of this value (16) reveals that the value
probably resulted from averaging the Cu content of
"normal" (9 mg Cu kg-') and "deficient" (3 mg Cu
kg-') rice plants in a solution culture experiment. Users
of this information were cautioned that "the critical
content obtained from a greenhouse study is some-
times too high and not applicable to field crops" (25,
p. 185). The blue-green leaf Cu deficiency symptom
cited for rice (16) was not observed in the studies re-
ported herein. Copper in Y-leaves was approximately
the same as reported by Gilmour (10) for 'Starbonnet'
rice. Straw Cu was as great as that reported by Gil-
mour for the final whole plant sample, or reported
elsewhere for straw (25), with the exception of 1983.
Furthermore, Everglades growers long have been aware
of the need for Cu fertilization (1) and most fertilize
regularly with CuSO4. For example, the grower who
cooperated in the present studies applied Cu at 2.2 kg
ha-' prior to the sugarcane crops that preceded the
rice. By comparison, at the highest rate of slag (20 Mg
ha-') only 0.3 kg Cu ha-' was applied (Table 1). Ad-
ditionally, slag application had no significant effect on
the Cu content of Y-leaves or of straw. Therefore, it
seems unlikely that Cu, as a contaminant of slag, was
responsible for the large yield increases observed with
slag application.
Thus, it does not appear that rice yield increases
can be accounted for by elements, other than Si, ex-


amined in this study that were contained in the slag.
This agrees with sugarcane studies in the Everglades
(7). Furthermore, there was no significant (P <0.10)
increase in yield over the check treatment when lime,
iron sulfate, or superphosphate were applied preplant
in 1982 at rates designed to equal the Ca, Fe and P
rates, respectively, that were associated with slag ap-
plication of 20 Mg ha '. The check, lime, Fe, and P
treatments produced rough-rice yields of 5.3, 5.3, 5.2,
and 5.4 Mg ha-', respectively.
The evidence obtained in these studies suggests that
the main effect of slag was to provide plant available
Si; The low native Si status of the Histosols used in
these studies appears to be a factor that greatly limits
rice yields. It may be worthwhile to consider Si fer-
tilization in other Histosols where difficulties are en-
countered with rice production.

ACKNOWLEDGMENT
The authors wish to express their appreciation to Mr.
Manuel Porro, Seminole Sugar Corp., for providing the study
sites and maintaining the rice crops. Technical assistance by
Mr. Nemrod Relph, Ms. Theresa Sanford, Ms. Myrine Hew-
itt, Ms. Rosa Innocent, Ms. Barbara Curry, Ms. Esther Fi-
gueiras, Ms. Fara Hernandez, Mr. Larry Schwandes, and Mr.
Curtis Elliot also is gratefully acknowledged, as is the assis-
tance of Mr. Norman Harrison with data processing and of
Dr. Don Myers and Ms. Elsa Garcia with the Helmintho-
sporium oryzae B. de Hann study.

REFERENCES
1. Allison, R.V., O.C. Bryan, and J.H. Hunter. 1927. The stimu-
lation of plant response on the raw peat soils of the Florida
Everglades through the use of copper sulphate and other chem-
icals. Univ. Florida Agric. Exp. Stn., Gainesville, FL. Bull. 190.
2. Bair, R.A. 1966. Leaf silicon in sugarcane, field corn, and St.
Augustine grass grown on some Florida soils. Proc. Soil Crop
Sci. Soc. Fla. 26:64-71.
3. Cate. R.B. Jr.. and L.A. Nelson. 1971. A simple statistical pro-
cedure for partitioning soil correlation data into two classes.
Soil Sci. Soc. Am. Proc. 35:658-660.
4. Driessen, P.M. 1978. Peat soils. p. 763-779 In F.N. Ponnam-
peruma (ed.) Soils and rice. International Rice Research Insti-
tute, Los Baftos, Philippines.
5. Driessen, P.M., and M. Soepraptohardjo. 1974. Soils for agri-
cultural expansion in Indonesia. Soil Research Inst., Bogor, In-
donesia. Bull. 1, p. 63.
6. Elawad, S.H., and V.E. Green, Jr. 1979. Silicon and the rice


100-
0 1981
E 1982
901 0 1 83
[ T,
so i


a 06


B
ca


'0 Vw 0 0 *
0 C
in
ma B
i a
a
I -.--..-.


e.0 1.0 2.0 3.0 4.0 5.0 6.0


7.0 8.0


SI (DRG KG 3-
Fig. 1. Relationship between Si in rice straw at harvest, and grain
yield calculated in each of 3 yr as a percent of the maximum yield
obtained among plots receiving various rates of calcium silicate
slag. The data are partitioned according to the Cate-Nelson pro-
cedure (3) to determine the "critical" Si content of rice straw (3.0
dag Si kg straw).


1262


%. 4.


8







SNYDER ET AL.: SILICON FERTILIZATION OF RICE ON EVERGLADES HISTOSOLS


1263


Table 6. Influence of calcium silicate slag applications on rice plant tissue elemental content.
Year Crop Plant part Slage rate N P K Ca Mg Fe Mn Zn Cu
Mg ha-' dag kg-- mg kg''
1981 First Y-leaf 0 3.00 0.33 1.67 0.26 0.28 84 587 41 8
10 2.88 0.32 1.65 0.20 0.22 93 345 37 7
Significance t NS NS ** ** NS ** NS NS
Straw 0 1.10 0.21 1.00 0.26 0.19 97 220 80 3
10 0.97 0.20 0.97 0.20 0.15 97 204 63 3
Significance NS ** ** NS NS ** NS
Ratoon Straw 0 0.88 0.12 1.00 0.45 0.17 125 91 43 13
10 0.70 0.11 .1.08 0.42 0.15 126 93 38 13
Significance ** NS N NS t NS NS NS NS
1982 First Y-eaf 0 3.45 0.33 1.91 0.25 0.14 74 36 30 5
2.5 3.27 0.31 1.94 0.19 0.13 74 30 29 6
5 3.05 0.31 1.98 0.18 0.13 81 26 29 4
10 3.05 0.30 1.95 0.17 0.12 62 24 28 5
20 3.27 0.31 1.95 0.17 0.13 75 19 28 4
Treatment effects
Linear ** ** NS NS NS NS
Quadratic ** ** NS NS NS NS NS
Straw 0 1,76 0.30 1.63 0.58 0.18 90 55 44 3
2,5 1.61 0.29 1.67 0.53 0.18 80 46 46 4
5 1.40 0.25 1.73 0.54 0.17 80 52 49 4
10 1.25 0.22 1.80 0.40 0.14 76 42 34 3
20 1.46 0.23 1.65 0.44 0.15 81 39 36 3
Treatment effects
Linear ** ** ** NS NS NS
Quadratic NS t t NS NS NS
1983 First Straw 0 1.08 0.13 1.21 0.31 0.15 79 54 38 1
5 0.92 0.13 1.53 0.25 0.14 73 49 44 1
20 0.87 0.11 1.74 0.23 0.14 71 41 36 I
Treatment effects
Linear NS ** ** NS NS NS ** NS
Quadratic ** NS ** NS NS NS ** NS
Ratoon Straw 0 0.78 0.07 1.27 0.21 0.14 69 98 38 1
5 0.81 0.08 1.31 0.17 0.13 65 82 35 2
20 0.74 0.09 1.49 0.17 0.12 59 63 29 1
Treatment effects
Linear NS NS NS ** NS NS ** NS NS
Quadratic NS NS NS ** NS NS NS NS
*,**,t Statistical significance at P <0.05, 0.01, and 0.10, respectively.


plant environment: A review of recent research. II Riso 28:235-
253.
7. Elawad, S.H., G.J. Gascho, and J.J. Street. 1982. Response of
sugarcane to silicate source and rate: I. Growth and yield. Agron.
J. 74:481-484.
8. Gascho, GJ., and H.J. Andries. 1974. Sugarcane response to
calcium silicate slag applied to organic and sand soils. Int. Soc.
Sugar Cane Technol. Proc. p. 15:543-551.
9. Gascho, G.J. 1976. Silicon status of Florida sugarcane. Proc.
Soil Crop Sci. Soc. Fla. 36:188-191.
10. Gilmour, J.T. 1977. Micronutrient status of the rice plant: I.
Plant and soil solution concentrations as a function of time.
Plant Soil 46:549-557.
11. Green, V.E. Jr., 1957. The culture of rice on organic soils-a
world survey. Agron. J. 49:468-472.
12. Hallmark, C.T., L.P. Wilding, and N.E. Smeck. 1982. Silicon.
In A.L. Page et al. (ed.) Methods of soil analysis, Part 2. 2nd
ed. Agronomy 9:263-273.
13. International Rice Research Institute. 1978. Nutritional prob-
lems of rice grown on Histosols. p. 277-279. In Annual report.
Los Banos, Laguna, Philippines.
14. Ikehashi, H., and F.N. Ponnamperuma. 1978. Varietal toler-
ance of rice to adverse soils. p. 801-825. In F.N. Ponnamper-
uma (ed.) Soils and Rice, International Rice Research Institute,
Los Baftos, Laguna, Philippines.
15. Ismunadji, M., and G. Soepardi. 1984. Peat soils problems and
crop production, p. 489-502 In S. Banta (ed.) Organic matter
and nee. International Rice Research Institute, Los Banos, La-
guna, Philippines.
16. Karim, A..M.B., and J. Vlamis. 1982. Micronutrient defi-
ciency symptoms of rice grown in nutrient culture solutions.
Plant Soil 16:347-360.
17. Lechler, P.J., W.R. Ray, and R.K. Leininger. 1981. Major and


trace element analysis of 12 reference soils by inductively cou-
pled plasma-atomic emission spectrometry. Soil Sci. 130:238-
241.
18. Lowther, J.R. 1980. Use of a single H2SO,-H3O, digest for the
analysis of Pinus radiata needles. Commun. Soil Sci. Plant Anal.
11:175-188.
19. McCollum, S.H., O.E. Cruz, L.T. Stem, W.H. Wittstruck, R.D.
Ford, and F.C. Watts. 1978. Soil survey of Palm Beach County
area, Florida. USDA-SCS West Palm Beach, FL, and Univer-
sity of Florida, Gainesville, FL.
20. SAS Institute, Inc. 1982. SAS user's guide: Statistics. 1982 ed.
SAS Institute, Cary, NC, p. 584.
21. Shih, S.F., G.S. Rahi, G.S. Snyder, D.S. Harrison, and A.G.
Smajstria. 1983. Rice yield, biomass, and leaf area related to
evapotranspiration. Trans. ASAE 26:1458-1464.
22. Shuler, K.D., G.H. Snyder, J.A. Dusky, and W.G. Genung. 1981.
Suggested guidelines for rice production in the Everglades Area
of Florida. Everglades Research and Education Center, Belle
Glade, FL, p. 9.
23. Takijima Y., and S.D.I.E. Gunawardena. 1969. Nutrient defi-
ciency and physiological disease of lowland rice in Ceylon. I.
Relationships between nutritional status of soil and rice growth.
Soil Sci. Plant Nutr. (Tokyo) 15:259-266.
24. Tanaka, A., and S. Yoshida. 1970. Nutritional disorders of the
rice plant in Asia. p. 14-15. International Rice Research Insti-
tute, Los Baftos, Laguna, Philippines. Tech. Bull. 10.
25. Yoshida, S. 1981. Fundamentals of rice crop science, p. 185-
186. International Rice Research Institute, Los Baifos, Laguna,
Philippines.
26. Yoshida, S., D.A. Forno, J.H. Cock, and K.A. Gomez. 1976.
Laboratory manual for physiological studies of rice. 3rd ed. In-
ternational Rice Research Institute, Los Baflos, Laguna, Phil-
ippines.














Sp'r"E s CoipL;-.no a.nd .e.. '. dancee of Stink Bugs
(Heteroptera: Pentatomidae) in Southern Florida Rice

D. B: JONES AND R. H. CHERRY
Institute of Food and Agricultural Sciences, Everglades Research and Education Center,
University of Florida, P.O. Drawer A, Belle Glade, Florida 33430


J, Econ. Entomol. 79: 1226-1229 (1986)
ABSTRACT Stink bugs were sampled with sweep nets in eight southern Florida rice fields
during 1983 and 1984. Four stink bug species were found; of these, Oebalhs pugnax (F.),
composed >95% of the total population. Stink bugs were found continuously in rice fields
from June through November. Population densities increased rapidly in rice fields at heading
and were most abundant during the grain-filling period in both main and ratoon crops.
Populations increased rapidly in fields because of adult migration and egg hatch. Populations
of stink bugs greater than economic threshold levels were found in 50% of the main-crop
and 100% of the ratoon-crop fields studied.
KEY WORDS Oebalus pugnax, rice, ratoon rice, population sampling


RICE RECENTLY has been reintroduced into the
Everglades Agricultural Area (EAA) of southern
Florida after a 20-year absence. In 1985, rice was
grown on ca. 4,000 ha in the EAA with an esti-
mated value of $4.5 million. Little is known about
insect pests of the crop in the EAA. Although many
different insects can be found in rice fields in the
EAA, stink bugs are currently considered the most
important pest. Green et al. (1954) reported find-
ing four species of stink bugs in Florida rice fields
in the 1950's but gave no information on their
relative abundance. More recently, Genung et al.
(1979) reported that five species could be found in
rice in the 'EAA, but again no information was
given on their relative abundance or seasonal oc-
currence. The species found by Genung et al.
(1979) were the rice stink bug, Oebalus pugnax
(F.); the southern green stink bug, Nezara crvidul
(L.); Mormidea pictiventris StAl; Euschistus
ictericus (L.); and Proxys punctulatus (Palisot de
Beauvois).
The seasonal occurrence of the rice stink bug in
the traditional southern United States rice-grow-
ing areas has been previously studied by Douglas
(1939), and Odglen & Warren (1962). Both the
adult and nymphal s'<:r.: of stink bugs feed on
individual grains of rice as the panicle develops
(Douglas 1939, Swanson & Newsom 1962, Bowling
1979). Stink bug damage to rice is also well doc-
umented (Douglas & Tullis 1950, Swanson & New-
som 1962, Marchetti i &J). Current recommen-
dations given by state extension agencies in other
rice-growing states are to apply insecticides when
infestation levels reach 25 stink bugs per 10 sweeps
during the first 2 weeks after 75%.heading paniclee
-";.; .CIn--) and 10 stink bugs per 10 sweeps after
t ,. time (Dre, 1983, Hamer 1983, Johnson et al.
- .4) Ho. -ver, Bowling (1982) reported a per-
t:':-nt.e -:I.; ol $223.30 in Texas based on value


factors and harvested yields with a population
density of 3.7 stink bugs per 10 sweeps.
Currently, Florida rice growers spray insecti-
cides for stink bug control as based on guidelines
from areas outside Florida. Because the southern
Florida climate and environment are different than
those of other southern rice-growing areas, the
guidelines may be inappropriate. Ratooning of rice,
the practice of obtaining a second crop from the
stubble of the main crop, is also commonly prac-
ticed in the EAA. This practice extends the rice-
growing season in Florida to later dates than in
other ri ce--..',-in areas of the United States. Vir-
tually no information is currently available on stink
bug activity in ratoon rice. Stink bugs have also
I -.i-'r.-. in large numbers in some rice fields
shortly after spraying. Factors such as migration
from adjacent habitat, improper insecticide appli-
cation, or pest resurgence caused by pesticide-in-
duced mortality of natural enemies (Bowling 1962)
may be responsible for the reinfestation.
The objectives of our study were to 1) determine
the relative abundance of stink bug species in
southern Florida rice fields, 2) determine the
abundance of stink bugs with respect to calendar
date and crop growth stage, and 3) develop pos-
sible explanations for rapid population increases of
stink bugs in rice fields after insecticide spraying.

Materials and Methods
Eight commercial rice fields of Oryza sativa L.
'Lebonnet' in the EAA were sampled each year
with sweep nets (38.1 cm diam.) during the 1983
and 1984 :',wiivF seasons. Two fields were paired
at each ot four locations each year. Fields were
ca. 16 ha and located throughout the EAA to ob-
tain a representative sample of insect populations
in the area. Fields also represented the range of


1226













JONES & CHERRY: STINK BUGS IN FLORIDA RICE


Table 1. Relative abundance of stink bugs found in
southern Florida riee fields in 1983 and 1984

Adults Nymphs Total
Species -
No. % No. % No. %
0. pugnax 3,328 92.8 2,728 99.1 6,056 95.6
M. ptctiventrts 105 2.9 0 0.0 105 1.6
N. oiridula 68 1.9 24 0.9 92 1.5
E. cterkcus 85 2.4 0 0.0 85 1.3
Total 3,586 100.0 2,752 100.0 6,338 100.0


normal planting dates. Planting dates for the fields
ranged from 1 March through 12 May in 1983 and
from 8 March through 4 May in 1984. Heading
date was based on visual observation and the field
was considered headed when at least 50% of the
plants had emerged panicles. Heading dates of
fields sampled during the study ranged from 15
June to 24 July for the main crop and from 18
September to 20 October for the ratoon crop. Of
the 16 fields sampled over the 2-year period, 10
were ratoon-cropped. Growers applied insecticide
as they deemed necessary; therefore, application
times varied considerably. All fields in the main
crop were.sprayed at least once, and twice in 10
of 16 fields. Insecticides were generally applied at
early heading (1-5% headed) or 10 days from 50%
heading, or both. None of the ratoon fields was
treated with insecticides.
Sampling began 3 and 6 weeks after planting in
1983 and 1984, respectively, and continued through
harvest. Samples were taken from ca. 1000 to 1500
hours (EDT). Each field was sampled weekly; each
sample consisted of 100 consecutive sweeps (1800).
Each horizontal stroke with the net in either di-
rection was one sweep and one sweep was made
with each forward step. Sampling began at least
50 m into the field from the roadside and was
centered between the field levees to avoid possible
edge effects (Douglas 1939). After collection, in-
sects were frozen for later counting. Both adult
and nymphal stages of stink bugs were counted.


1 It 21 I 11 21 t 1 1 I 1 l 21 1 i1 21 1
JU4E JULY PUG. SEPT. CCT. NOV.
Fig. 1. Seasonal distribution of 0. pugnax in south-
ern Florida rice fields. Vertical bars, SE.


DRAS FROM MATIN-CROP HERDING
Fig. 2. Abundance of 0. pugnax with respect to
crop growth stage (days from 50% heading of main crops)
in southern Florida rice fields. Vertical bars, SE.


Only counts of 0. pugnax were used for the sea-
sonal and crop growth stage determinations since
our data showed that this species was clearly the
most abundant (>95%) species of pest stink bug
in rice fields.

Results and Discussion
The relative abundance of stink bugs in 1983
and 1984 is given in Table 1. The rice stink bug
was the most abundant species, composing 95.6%
of the total stink bugs captured. Three other species
accounted for the remaining 4.4% of stink bugs
sampled. The same four species were reported in
Florida rice by Green et al. (1954) > 30 years ago.
A fifth species, P. punctulatus, found in Florida
rice by Genung et al. (1979) was not observed. The
rice stink bug composed 99,1% of nymphs sampled
and only one other species of nymphal stink bug,
N. viridula, was found in rice fields over the 2-year
period (Table 1). Two other species found, M. pic-
tiventris and E. ictericus, were clearly not breed-
ing in rice fields.
Rice stink bugs were not found in rice fields


IS 2l 25 9e


IB
DRYS FROM HEADING


Fig. 3.' Adult and nymphal populations of 0. pug-
nax occurring in southern Florida rice fields resulting
from migration.


38









a ..
r;9-5


October 1986


,1227










JOURNAL OF ECONOMIC ENTOMOLOGY


ie2

1-I
)go- TWA$nlr


/ \-
I -
F 3 /


-S 5il Z 25 4Se 5
DRTS FROM HERDING
Fig. 4. Adult and nymphal populations of 0. pug-
nax occuning in southern Florida rice fields resulting
from an egg hatch.


before early June (Fig. 1), even though sampling
had begun as early as 4 April in 1983. Rice stink
bugs in other southern rice-growing states emerge
from hibernation in late April or May and remain
on native grasses until the rice heads (Douglas 1939,
Odglen & Warren 1962). Heading first occurred
on 15 June and 27 June in 1983 and 1984, respec-
tively. After their initial migration into fields in
June, rice stink bugs were found in rice fields
throughout the entire sampling period, which last-
ed through early November, Nilakhe (1976) re-
ported that rice stink bugs in Louisiana began to
enter hibernation quarters in the 1st week of Oc-
tober, and the majority had entered by the 3rd
week. In our study, rice stink bugs actually in-
creased in number in rice fields during that time.
Seasonal population trends of rice stink bugs
were similar for both years of the study. Peak pop-
ulation numbers were found on 1 August and 21
July in 1983 and 1984, respectively. These dates
corresponded to periods when the rice fields were
fully headed. Population levels also became high
in the ratoon crop during October and November
in both years. The high population levels resulted
both from ratoon rice heading at this time and the
absence of insecticides used in the ratoon crop.
Rice stink bug abundance in relation to crop
growth stage based on days from heading (DFIH)
of the main crop is shown in Fig. 2. Very few rice
stink bugs were found earlier than 10 days before
heading (-10 DFH). Rice stink bug counts rose
rapidly at heading and remained fairly high up to
40 DFH with the exception of 10 DFH. Of 26
insecticide sprays, 18 were applied between 0 and
10 DFH, thus causing the decrease in rice stink
bugs at 10 DFH, Therefore, it appears that insec-
ticide applications currently used by rice growers
in the EAA are effective, even though the popu-
lation reduction is only temporary. The main crop
is generally harvested 30-40 days after heading,
which explains the decline in rice stink bugs found
at. that time. Ratoon crop heading of rice occurs
40-50 days after harvest of the plant crop (80-90


Vol. 79, no. 5


1228


DFH), but is typically less synchronous than that
of the main-crop. Stink bugs were found to in-
crease steadily from 50 to 80 DFH of the main
crop, then increase rapidly from 80 to 110 DFH.
The latter period corresponded to the grain filling
period of the ratoon crop. Of the 16 fields sampled
during the 2-year period, 8 exceeded currently ac-
cepted economic threshold levels in the main crop.
All 10 of the ratoon crop fields studied, none of
which received insecticide application, exceeded
economic threshold levels.
Rice stink bug populations can increase rapidly
in southern Florida rice fields, either because of
adult migration into a field or egg hatches within
the field, or both. Both causes were observed dur-
ing this study. Fig. 3 illustrates mean rice stink
bug densities in a pair of fields that had no stink
bugs present until 1 week before heading. A rapid
increase in rice stink bugs occurred during the next
2 weeks. This increase coincided with the harvest
of a nearby rice field that may have harbored a
sizeable adult population. The population decline
from 10 to 15 DFH was due to spraying of insec-
ticides.
Fig. 4 illustrates the increase of rice stink bugs
in a pair of rice fields because of an apparent hatch.
A few adult stink bugs began appearing in the rice
shortly after heading. An insecticide was applied
at 10 DFH even though rice stink bug numbers
had not reached economic threshold levels. Shortly
thereafter, rice stink bug nymphs began to in-
crease rapidly in numbers and outnumbered adults.
The increase can be attributed to egg hatch be-
cause the nymphs are wingless and unable to trav-
el long distances. Rice stink bugs reached econom-
ic threshold levels ca. 2 weeks after the insecticide
was applied. Therefore, rice stink bug populations
can increase rapidly in southern Florida rice fields
by either adult migration or hatches from eggs
within fields, or a combination of both.
The rice stink bug is clearly' the predominant
stink bug species in rice fields of southern Florida.
Rice stink bugs were detected continuously in rice
fields from as early as 10 June to as late as 10
November. Rice stink bug populations increased
rapidly in rice fields at heading and were most
abundant during the grain-filling period in both
main and ratoon crops, frequently reaching eco-
nomic threshold levels in both crops. Rice stink
bug population densities can increase rapidly when
large numbers of adults migrate into fields. Fields
can also reach economic threshold levels of rice
stink bugs through the hatching of eggs after in-
secticide application. Therefore, growers need to
monitor fields for rice stink bugs on a regular basis
during the grain-filling period, in both main and
ratoon crops, even after previous treatments.

Acknowledgment
We express our appreciation to D. B. Stanford for his
technical assistance in both the field and laboratory. This
is Fla. Agric. Exp. Stn. Journal Series No. 7225.










JONES & CIERBIY: STINK


References Cited
Bowling, C. C. 1962. Effect of insecticides on rice
stink bug populations. J. Econ. Entomol. 55: 648-
651.
1979. The stylet sheath as an indicator of feeding
activity of the rice stink bug. J. Econ. Entomol. 72:
259-260.
1982. Economic evaluation of rice stink bug damage,
p. 42. In Proceedings, 19th Rice Technical Working
Group, Hot Springs, Ark., 23-25 February 1982.
Douglas, W. A. 1939. Studies of rice stink bug pop-
ulations with special reference to local migration. J.
Econ. Entomol. 33: 300-303.
Douglas, W. A. & E. C. Tullis. 1950. Insects and
fungi as causes of pecky rice. U.S. Dep. Agric. Tech.
Bull. 1015.
Drees, B. M. 1983. Insect management, pp. 18-23.
In 1983 Rice production guidelines. Texas A&M
Univ., College Station.
Genung, W. G., G. H. Snyder & V. E. Green, Jr. 1979.
Rice field insects in the Everglades. Belle Glade Res.
Rep. EV-1979-7. Univ. of Florida, Gainesville.
Green, V. E., Jr., W. H. Thames, Jr., A. E. Kretseh-
mer, Jr., A. L. Craig & E. C. Tullis. 1954. Rice
investigations, pp. 235-236, In Annual Report of Ag-


October 1986


BUGS IN FLOlIDA RICE 1229

riculture Experiment Station, Univ. of Florida,
Gainesville, 30 June 1954.
Iamer, J. 1983. Rice stink bug. Mississippi Cooper-
ative Extension Service, Mississippi State Univ., Mis-
sissippi State.
Johnson, D. R., J. J. Kimbrough & M. L. Wall. 1984.
Control of insects attacking rice. Arkansas Coop. Ext.
Ser. EL 330.
Marehetti, M. A. 1980. Studies of brown spot, stink
bugs, pecky rice and their relationships, pp. 57-58.
In Proceedings, 18th Rice Technical Working Group,
Davis, Calif., 17-19 June 1980.
Nilakhe, S. S. 1976. Overwintering, survival, fecun-
dity, and mating behavior of the rice stink bug. Ann.
Entomol. Soc. Am. 69: 717-720.
Odglen, G. E. & L. O. Warren. 1962. The rice stink
bug, Oebalus pugnax (F.), in Arkansas. Arkansas
Agric. Exp. Stn. Rep. Ser. No. 107.
Swanson, M. C. & L. D. Newsom. 1962. Effect of
infestation by the rice stink bug, Oebalus pugnax,
on yield and quality of rice. J. Econ. Entomol. 55:
877-879.

Received for publication 24 December 1985; accept-
ed 19 May 1986.


*/:









Response of a Rice-Sugarcane Rotation to Calcium
Silicate Slag on Everglades Histosols'

D. L. Anderson, D. B. Jones, and G. H. Snyder2


ABSTRACT
Rice (Oryta sativa L.) and sugarcane (Saccharam spp.), grown on
organic sells of the Everglades, have been shown to respond favor-
ably to the application of SI from calcium silicate slag. Since these
crops may be grown in rotation, it is important to know if slag applied
to one crop will benefit the second crop. The objective of the study
was to determine the response of rice and sugarcane grown on a
Terra Cela muck (Euic, hyperthermic Typic Medisaprist) to calcium
silicate slag applied prior to planting rice, and to slag applied before
the planting of sugarcane. Five rates of slag were applied for pro-
duction of a rice crop, after which time the same plots were planted
to sugarcane. Other plots received the same rates of slag just prior
to planting sugarcane. Slag applications increased both rice straw
Si and sugarcane leaf Si concentration. A single application of slag
prior to planting rice increased production of both the rice and sug-
arcane crops in the rotation. The combined plant and ratoon rice
grain yields were significantly increased 50% by slag application.
Slag application also increased harvested cane (biomass) yields 23%,
and sugar yields by 25%. Somewhat greater sugarcane plant re-
sponses were observed from slag applied immediately before planting
than from slag applied before the rice and cane rotation treatment.
On the average, slag applied at 20 Mg ha'- before rice increased
sugar yield by 16%, compared to a 21% increase when slag was
applied before cane.
Additoarl index words: Florida, Leaf silicon content, Organic sells,
Orya stive L., Rie yields, Saccharum L., Silicon, Soluble silicon,
Sugar yields.

SILICON is a functional nutrient that, under certain
conditions, increases plant growth. The impor-
tance of Si for plant growth and production was dis-
cussed by Elawad and Green (1979), Lewin and Rei-
mann (1969), and Mengel and Kirkby (1982, p. 548-
552). In South Africa, sugarcane (Saccharum spp.) re-
sponded to soluble silicate application (Du Preez,
1970). In Hawaii, silicate slags have been used to in-
crease yields of various agronomic crops (Plucknett,
1972, p. 203-223).
Sugarcane and rice (Oryza sativa L.) yields have been
increased by application of calcium silicate slag to His-
tosols in the Everglades Agricultural Area (EAA) (Gas-
cho and Andreis, 1974; Snyder et al., 1986b). Leaf Si
contents of sugarcane grown in the EAA were observed
to be below or near Si levels that limited sugarcane
production in Hawaii (Bair, 1966; Gascho, 1976; Gas-
cho, 1977). Leaf freckling is a symptom associated with
low leaf Si levels (Elawad et al., 1982). It was shown
that silicate slag applied on organic and mineral soils
of the EAA reduced leaf freckling and increased sug-
arcane and sugar yields (Gascho and Andreis, 1974;
Elawad et al., 1982). Further studies showed that ap-
plication of silicate materials increased plant height,
stem diameter, tillering, and cane and sugar yields in
both the plant and ratoon crops (Elawad et al., 1982).
Rice yields were increased on organic soils of the EAA

Contribution from the University of Florida Institute of Food
and Agricultural Sciences. Agric. Exp. Stn. Journal Series no. 7461.
Received 28 July 1986.
Assistant ofessors and professor, respectively, Everglades Res.
Ed. Ctr., P.O. Drawer A, Belle Glade, FL 33430.
Published in Agron. J. 79-531-535 (1987).


in excess of 30% following preplant application of sil-
icate slag, and positive linear relationships between
straw Si concentration and grain yields were observed
(Snyder et al., 1986b). In these studies, rice receiving
calcium silicate slag application had greater height,
greater number of panicles per square meter, greater
kernel weight, and less disease. Nevertheless, calcium
silicate slag is sufficiently expensive that its commer-
cial use for rice production alone is questionable (J.
Alvarez, 1986, personal communication).
Rice and sugarcane are grown in rotation in the EAA
on approximately 4000 ha. From this rotation, both
economic and agronomic benefits have been observed
(Alvarez and Snyder, 1984; Snyder et al., 1986a). If
slag applied to rice also benefits the sugarcane crop
that follows rice, then the economics associated with
slag use for rice are more favorable. The objective of
this study was to determine the response of rice and
sugarcane grown in rotation, to calcium silicate slag
applied prior to planting rice, and to slag applied be-
fore the planting of sugarcane.

METHODS AND MATERIALS
Rice
Two studies were conducted at locations approximately 5
km. apart in the eastern EAA. The soil in both studies was
a Terra Ceia muck (Euic, hyperthermic Typic Medisaprist),
a Histosol that accounts for about 40% of the Everglades
under cultivation (McCollum et al., 1978). Total Si was 10
and 7 g kg- soil in Studies I and 2, respectively. The calcium
silicate slag (Table 1) used was a by-product of electric fur-
nace production of elemental P. The slag was broadcast in
commercial rice fields at rates of 0, 2.5, 5, 10, and 20 Mg
ha~'. The slag was incorporated into the soil by tilling to an
approximate depth of 15 cm on 12 Apr. 1984 in Study 1 and
on I May 1984 in Study 2, prior to seeding cv. Lebonnet
rice on 17 Apr. 1984 and 2 May 1984 for Studies I and 2,
respectively. The rice was commercially seeded at 100 kg
ha-' in rows spaced at 18 cm. Plot size was 6.1 by 10.0 m,
and a randomized complete block design with four repli-
cations was used. Iron sulfate (Iron-Sul heptahydrate,3 1.2%
K, 30% S, 20% Fe; Western Ag-Minerals Co., Houston, TX)
was drilled with the seed at approximately 100 kg source
material ha-' in both studies. As per commercial practice
for rice grown organic soils in the EAA, no other fertilizer
was used.
Fields were flooded approximately 4 weeks after seedling
emergence until 2 weeks before the plant crop harvest. Fields
were maintained using standard cultural techniques (Shuler
et al., 1981). On 7 Aug. 1984, the rice grain and straw in

Table 1. Chemical analyses (dg kg-' of TVA calcium silicate slag
ud In the studies. .....
P K Mg Ca Fe Si Al S Na
0.52 0.42 0.20 20.0 0..99 20.60 5.18 0.37 0.15
t Analyses by Alabma Tst ang Laboratories, Birmingham, AL 35202.

1 Mention of a trade name or commercial product does not con-
stitute endorsement for use by the University of Florida.







AGRONOMY JOURNAL, VOL 79, MAY-JUNE 1987


Study I were harvested by combining four rows, 10 m long,
in the center of each plot. On 22 Aug. 1984, rice grain in
Study 2 was harvested by hand from two rows, 4 m long,
in the center of each plot. Grain was threshed and the straw
was retained. Following harvest, the fields were reflooded for
ratoon rice crop production. The same cultural and hand
harvesting techniques were used for the ratoon crop in Study
1 on 24 Oct. 1984.
Harvested grain was weighed, and moisture was deter-
mined with a commercial grain moisture meter. Yields were
calculated as unhulled rice (rough-rice) at 120 g kg- mois-
ture. Straw Si concentration was determined by dry ashing
1.00-g portions at 5500C, following pretreatment with HNO3.
After washing with HC, the residue was reignited at 550*C,
and the final residue weighed as SiO2. Data are reported as
Si in units of dag kg-'.
Sugarcane
After rice production, slag was broadcast at 2.5, 5, 10, and
20 Mg ha-' on 16 of the 20 plots left without applied slag
on 14 Nov. 1984 and 16 Dec. 1984 in Studies 1 and 2,
respectively, which thereby created the before-cane treat-
ments. All plots were prepared for sugarcane planting by
rototilling and furrowing so that each plot contained four
rows on 1.5-m spacings by 10 m long. Phosphorus, K, Mn,
Zn, Cu, and B were applied in the furrows of all plots at 40,
100, 5.6, 2.2, 2.2, 1.1 kg ha-', respectively. Double rows of
sugarcane stalks (cv. CP72-1210), cut to 46-cm lengths, were
placed in the furrows and covered on 17 Dec. 1984 and 19
Dec. 1984 in Studies 1 and 2, respectively. All cultural prac-
tices were the same as those maintained in commercial fields
(Institute of Food and Agricultural Sciences, 1983, p. 101-
116). Twenty top visible dewlap (TVD) leaf blades, with
mid-ribs (Thein and Gascho, 1980), were collected from each
plot in Studies I and 2, on 3 June and 20 June 1985, re-
spectively. Analysis for Si concentration in sugarcane leaf
samples was determined as described previously for rice tis-
sues.
Sugarcane harvesting in Studies 1 and 2 occurred on 31
Jan. and 17 Feb. 1986, respectively. Cane was burned to
remove excess leaves and trash, and whole stalks were cut
by hand at the soil surface. Tops were removed by cutting
at the top hard internode. After the sugarcane stalks from
each plot were weighed, 15 stalks per plot were randomly
collected and passed through a three-roller sample mill for
juice extraction. The crusher juice was analyzed for Brix
e.e y-t. s sO.sex-.eseasi
ntt-a.@ statO.*&
6.0 -



4.8 -o. 70s smx o ^
/ a L yo.s.gatn .sta teric.oii



4.2- o ase.-0 89"o.40
.W Location 1., plant Rp


Locations 1, rtoon rie --.- C
.0- / / Location plant rice a


(soluble solids) using a Bausch & Lomb refractometer (Bausch
& Lomb, Inc., Rochester, NY). After clarifying the juice us-
ing lead subacetate (Meade and Chen, 1977, p. 541), the Pol
(juice sucrose concentration) was determined using a Ru-
dolph Autopol IIS automatic saccharimeter (Rudolph Re-
search, Flanders, NJ). The percent sucrose in juice was es-
timated using formulas developed from sucrose tables given
by Meade and Chen (1977, p. 882-885) and temperature
Brix correction tables by Meade and Chen (1977, p. 861-
962):
Sucrose
- (Pol X 26)/{105.811 + [(CBrix 15) X 0.44]};
where the 20C temperature correction for Brix is given:
CBrix = Brix + (temperature 20) X 0.075.
Juice purity was calculated as a percent of the ratio of sucrose
to Brix. Recoverable 96* sugar was calculated using the Win-
ter-Carp-Geerligs formula modified by Arceneaux (1935), and
the varietal correction factor (VCF) for cv. CP72-1210 given
by Glaz et al. (1985) and described by Rice and Hebert (1972):
96 Sugar
= [(Sucrose X 21.058) (Brix X 6.15)] X VCF.
From the measured cane (biomass) tonnage (kg ha-') and
theoretically recoverable 96 sugar (kg sugar Mg cane-'), the
sugar yield was calculated (kg 96* sugar ha-'). The analyses
of variance (ANOVA) and standard error of regression (SER)
were used to evaluate main effects and regression analysis
of application rate effects, and were obtained using SAS
(Freund and Littell, 1981, p. 182-184; SAS Institute, 1982).

RESULTS AND DISCUSSION
tRce
Calcium silicate slag increased Si concentration in
rice straw from the plant crop in both studies. The
coefficients of the linear and quadratic model terms
(Fig. 1) relating straw Si concentration to applied slag
rates were statistically significant (P<0.10). In the ab-
sence of applied slag, straw averaged 2.0 dag Si kg-'.
In a previous study (Snyder et al., 1986b), grain yields
of the plant crop were reduced when straw contained
a

}gl ~ plant rice
r $ 90.79
sea oc*

5

4 r'.o.Es
-F SER.0.42
S3 .. e .......... raston rice


-1
Stag (Mg ha )
Fig. 2. Effect of calciam silicate slag application on grain yields in
plant and ration rice crops in Study 1.


*f
Sla (Mg ha )
Fig. 1. Effect of calcdum silicate slag applicatice on rice straw Si
concentration


I






ANDERSON FT AL: M.ESPONSE OF RICE & SUGARCANE TO STAG


less than 3.0 dag Si kg-'. Straw Si in the ratoon crop
(Study 1) also increased with increasing slag applica-
tion rate (Fig. 1). No ratoon crop was harvested from
Study 2 for reasons explained below.
Slag application significantly (P rough-rice yield in the plant crop and ratoon crop of
Study 1 (Fig. 2). Slag applied at 20 Mg ha-' increased
plant crop rice grain yield by 44% and increased ratoon
crop grain yield by 67%.
A very uneven stand of rice was obtained in Study
2 because the experiment was inadvertently planted
in a surface depression in the commercial field. At the
time the field was first flooded, rice in the experimental
area was covered with water sufficiently deep that many
seedlings were killed. Excessive in-field variation in
this study was indicated by comparison of the coeffi-
cients of variation for Studies 1 and 2; 8.8 and 22.2
respectively. Probably for this reason, there was no
significant difference in rough-rice yield among treat-
ments in Study 2. However means for each slag rate
were similar to those obtained in Study I, with the
exception of the 20 Mg ha-' rate. Rough-rice yields
corresponding to slag rates of 0, 2.5, 5, 10, and 20 Mg
slag ha-' were 5.4, 5.5, 6.6, 7.0, and 6.6 Mg ha-',
respectively, in Study 2. Based on this trend, and the
straw Si concentration data, it appears that soil Si in
Study 2 probably was sufficiently low to limit rice
yields. The ratoon crop was not harvested at Study 2
because of the uneven plant crop stand.


Calcium silicate slag increased Si concentration in
sugarcane leaves. A significantly (P<0.01) greater re-
sponse occurred with slag applied immediately prior
to sugarcane planting than with slag applied before rice
(Table 2 and Fig. 3). In the absence of applied calcium

Table 2. AnalyaJe of varlnce of sugarcaae yield comp n aent
sigaifleantly affected by t'rs s en'iot "C c:-1dr or rieUSL r'jf.
Study Yield component Saurce df Significance R
I Cans (Mg hal- Model 10 *" 0.52
Time$ I1
Rate a **
Time x Rate 3 NS
Sugar (Mg ha") Modl 10 0.42
Time 1 NS
Rate 8 *
Time x Rate 3 NS
Leaf Si (dag kg l Model 10 *0 0.89
Time 1 *
Rate 3 *
Time x Rate 8 "
2 Cane (Mg hbe-) Model 10 0.60
Time 1
Rato 3
Tima x Rate 3 NS
Sugar (Mg ha-" Model 10 ** 0.60

Time x Rate 3 NS
Leaf Si (dag kgt Model 10 *$ 0.88

Time x 3te *
0.*,t and NS w~ epWe sta en a tasee tlt P P >0.10, rwpectively.
t Tei reers to tIU meof rl:- e:e c.:!,- i'. ,r:-
balmw ica or befor s areaBe, .


silicate slag, the Si concentration in sugarcane leaves
averaged 1.2 and 1.6 dag kg-' in Studies 1 and 2,
respectively. In Studies I and 2, simple correlation (r,
P<0.10) of sugarcane yields (Mg ha-') with leaf Si
concentrations, respectively, were 0.45 and 0.44 when
slag was applied before the rice crop, and 0.56 and
0.43 when slag was applied immediately before the
sugarcane crop. Sugar yields (Mg ha-~) were not sig-
nificantly correlated with leaf Si levels in either study,
except in Study 2 when slag was applied immediately
prior to the sugarcane crop (r=0.42, P<0.10).'
Results of ANOVA (omitting the check plot to pro-
vide a balanced design) indicated that cane and sugar
yields were generally affected by the rate and time of
slag application, with no significant rate X time in-
teractions (Table 2). Crusher juice sucrose, Brix, juice
purity, stalk weight, and sugar yield per tonne of cane
were unaffected by slag application.
There was a consistent trend for greater cane and
sugar yields when slag was applied just before sugar-
cane planting (Fig. 4 and 5), and this trend was con-
sistent with that observed for the leaf Si data (Fig. 3).
However, in the case of cane and sugar, the effect of
time of application was small and not significant for
all rates of slag application. In Study 1, the time of
slag application had no effect on sugar yields, although
the rate of slag of application did have a significant
effect on sugar yields. As a result of slag application,
harvested cane increased from 10 to 23%, and sugar




ren.' S.-- 0.36

S 00

44
2 0 0 ..

2.0

.5 / /' .2 ^S


a ,or-" ca -.. e



0-8
,hefore fle *--* ..------





C' ,,/ ,S-R0.34 s

.1 ,002
/Study2
.6 0 "6 20

Slg (Me hi)
V ., Efect ef time and rate of cacam silteate slag application on
s~gars'e leaf Si coacentratien.







AGRONOMY JOURNAL, VOL. 79, MAY-JUNE 1987


F 0 .* g










f30 .-'/




120 0

B t o ,*' ,
sbugarane bless yield.










per hectare increased from 10 to 25% (Fig. 4 and 5).
In Hawaii, 55 to 72% of the applied Si was not uti-
lized by the crop even after 5 yr (Khalid and Silva,
1978). In the present studies, sugarcane continued to
benefit from a single application of silicate slag applied
before production of two rice crops. Surcane yield










responses were only slightly lower than yields in which
slag was ied immediately prior o planting s







arcane. For example, when averaged across both stud-
ies, slag applied at 20 .g ha-' before rice increased,

sugar (Mg ha- L) 16%, compared to a 21% increase when
slag was applied before cane. Since application nd
material costs may prohibit the use of sag before each


crop, the economic bnefita from a one-time appli-




cation for a long-term rice-sugarcane crop rotation sysld
tem appear better and are therefore currently being




investigated.
ACKNOWLEDGMENT S
ies, slag applied at 20 Mg ha- before rice increased
sugar (Mgha-) 16%, compared toa 21% increase when



We are gatefpl to M. Porro,. Seine Suar Cororation, a
investigated.


We are grateful to M. Porro, Seminole Sugar Corporation,
for his helpful suggestions, supply of labor, and contribution
of land for these studies. Partial support of these studies was
provided by the Potash and Phosphate Institute, Atlanta,
GA. Our appreciation is also extended to Dr. Frank G. Mar-
tin, Statistics Department, University of Florida, Gaines-
ville, for his manuscript suggestions, and to C. Miller, C. L.
Elliott, L P. Schwandes, E. A. Figueiras, F. Hernandez, N.
Relph, and N. L. Harrison for their technical support.

REFERENCES
Alvarez, J., and G.t. Snyder. 1984. Effect of prior rice culture on
sugarcane yields in Florida. Field Crop Res. 9:315-321.


o- o o"--

4. /


S // aSER 0.0*2

try
Study I

before cone ------
before rice -- ic ...

16 ," ..0. .

.0 .

y 15 R'81
A

Study 2

0 5 10 1 20o
Slag (9g h"1)
Fig. S. Effet of time and rate of calcium silicate slag application on
sugar yield (Mg ha'-).
Arceneaux, G. 1935. A simplified method of making theoretical
sugar yield calculations. In accordance with Winter-Carp-Geerligs
formula. Int. Sugar J. 37:264-265.
Bair, R.A. 1966. Leaf silicon in sugarcane, field corn and St. Au-
ustinegrass grown on some Florida soils. Proc. Soil Crop Sci.
Soc. Fa. 26:64-70.
Du Preez, P. 1970. The effect of silica on cane growth. Proc. S. Afr.
Sugar Technol. Assoc. 44:183-188.
Elawad, S.H., and G.J. Gascho, and J.J. Street. 1982. Response of
sugarcane to silicate source and rate. I. Growth and yield. Agron.
J. 74:481-484.
-- and V.E. Green. 1979. Silicon and the rice plant environ-
ment: A review of recent research. II Riso (Milano) 28(3):235-
253.
Freund, R.J., and R.C. Littell. 1981. SAS for linear models. SAS
Institute Inc., Cary, NC.
Gascho, G.J. 1976. Silicon status of Florida sugarcane. Proc. Soil
Crop Sci. Fla. 36:188-191.
- 1977. Response of sugarcane to calcium silicate slag. I.
Mechanisms of response in Florida. Proc. Soil Crop Sci. Soc. Fla.
37:55-58.
--- and H.J. Andreis. 1974. Sugarcane response to calcium sil-
icate slag applied to organic and sand soils. Int. Soc. Sugar Cane
Technol. 15:543-551.
Glaz, B., P.Y.P. Tai, J.L. Dean, M.S. Kang, J.D. Miller, and 0. Sosa,
Jr. 1985. Evaluation of new Canal Point sugarcane clones, 1984-
85 harvest season. USDA Agricultural Research Service, U.S.
Government Printing Office, Washington, DC.
Khalid, R.A., and J.A. Silva. 1978. Residual effects of calcium sil-
icate in tropical soils: II. Biological extraction of residual soil
silicon. Soil Sci. Soc. Am. J. 42:94-97.
Institute of Food and Agricultural Science. 1983. Florida agriculture
in the 80's. Sugarcane committee report. Gainesville, FL.
Lewin, J., and B.E.F. Reimann. 1969. Silicon and plant growth.
Annu. Rev. Plant Physiol. 20:289-304.
McCollum, S.H., O.E. Cruz, LT. Stem, W.H. Wittstruck, R.D. Ford,
and F.C. Watts. 1978. Soil survey of Palm Beach County area,
Florida. USDA-SCS, West Palm Beach, FL, and the University
of Florida (IFAS) Soil Science Department, Gainesville, FL.
Mead, G.P., and J.C.P. Chen. 1977. Cane sugar handbook. 10th ed.






TITKO ET AL.: VOLATILIZATION OF AMMONIA APPLIED TO TURFGRASS


John Wiley & Sons, New York.
Mengl, K., and E.A. Kirkby. 1982. Principles of plant nutrition.
3rd ed. International Potash Institute, Worblaufen-Bein, Switz.
erland.
Plucknett, D.L. 1971. The use of soluble silicates in Hawaiian ag-
riculture. Australian Soc. Soil Sci. 1(6):203-223.
Rice, E.R., and LP. Hebert. 1972. Sugarcane variety tests in Florida
during the 1971-72 season. USDA Agricultural Research Service
S-2. U.S. Government Printing Office, Washington, DC.
SAS Institute. 1982. Statistical analysis system. SAS Institute, Inc.,
Cary, NC.
Shuler, K.D., G.H. Snyder, J.A. Dusky, and W.G. Genung. 1981.
Suggested guidelines for rice production in the Everglades area of


Florida. Everglades Research and Education Center, Belle Glade,
FL.
Snyder, G.H., R.H. Caruthers, J. Alvarez, and D.B. Jones. 1986a.
Sugarcane production in the Everglades following rice. Proc. Am.
Soc. Sugar Cane Technol. 5:50-55.
-, D.B. Jones, and G.J. Gascho. 1986b. Silicon fertilization of
rice on Everglades Histosols. Soil Sci. Soc. Am. J. 50 1259-1263.
Thein, S., and G.J. Gascho. 1980. Comparison of six tissues for
diagnosis of sugarcane mineral nutrient status, p. 152-163. In
Proc. 16th Congr. Int. Soc. Sugar Cane Technol., Manila, Phil-
ippines. 1-11 Feb. 1980. International Society of Sugarcane Tech-
nologists, Print-Inn, Makati, Manila, Philippines.


Volatilization of Ammonia from Granular and Dissolved Urea Applied to Turfgrass'

Steve Titko, III, John R. Street, and Terry J. Logan2


ABSTRACT
Urea, applied in either granular or dissolved form, is a commonly
used N fertilizer source for turfgrass, and volatilization of NH3 pro-
duced by ures hydrolysis is considered to be a major contributor to
reduced N fertilizer utilization by established turf. Ammonia vola-
tilization losses from urea applied to turfgrass were studied in a
controlled environment chamber. Kentucky bluegrass (Poa pratensis
L, var. Merion) sod was placed on a Crosby silt loam soil (fine,
mixed, mesic Aeric Ochraqualfs) in 17.5-L plastic containers with
surface areas of 434 cm'. Covers fitted to the containers had intake
and exhaust ports such that air could be passed over the sod and
NH3 collected in a boric acid trap. Experiments were conducted to
examine the effects of temperature, relative humidity, wetting and
drying cycles, and irrigation on NH3 loss from surface-applied urea.
Ammonia losses were higher from granular than from dissolved area
in all cases, except where urea application was immediately followed
by a 25.4-mm irrigation. Ammonia loss from granular and dissolved
urea increased as temperature increased from 10 to 22.2*C, but there
were no significant effects on NH3 loss as temperature increased
from 22.2 to 32.2C. Ammonia losses from dissolved urea at 68%
R.H. were greater than losses at 31% LRH, but NH3 loss from
granular urea was not significantly affected by relative humidity.
Ammonia losses increased rapidly following periodic wetting of the
turf fertilized with dissolved urea. Irrigation (25.4 mm) following
urea application decreased NH3 losses from both dissolved ad Sran-
ular ureas.
Additional index words Nitrogen fertilizer, Kentucky bluegrass,
Nutrient losses, Poa prarenais L.

N ITROGEN fertilization is an important cultural
practice in turfgrass management. Recent in-
vestigations into N utilization by plants have indicated
that a substantial portion of the N applied is appar-
ently lost and that crop recovery is often less than 50%
(Torello et al., 1983). Nitrogen may be lost from turf-
grass via many avenues including leaching, denitrifi-
cation, volatilization, and immobilization.
Urea [CO(NH2)2]. is the most popular N source of
the turfgrass industry because of its high N content,
ease of handling, and low cost. Urea undergoes en-
zymatic hydrolysis to form ammonium carbonate,
which is very unstable and decomposes to form NH3:
urcasc
CO(NH2)2 + H + 2H20 -- 2NHI [1)
+ HCOT0
HCO- + H+ C02(g) + H20 [2]
NHW + OH- NH4OH = NH3(g) + H20 13]


Literature values regarding the magnitude of NH3 vol-
atilization losses from urea applied to turf are incon-
sistent. Volk (1959) found significant volatilization
losses from urea applied to turf-covered soils; N losses
from surface-applied pelleted urea reached 20 to 30%.
Nelson et al. (1980) reported volatilization losses of
39% of urea-N applied to thatchy turf, while Torello
et al. (1983) found only 1.6 and 4.6% volatilization
losses from prilled- and liquid-applied urea on turf,
respectively.
Factors affecting NH3 volatilization have been ex-
amined by Denmead et al. (1974), Mills et al. (1974),
Fenn (1975), Terman (1979), and Nelson (1982).
Among the important variables affecting NH3 volatil-
ization are microenvironment pH, soil moisture, tem-
perature, fertilizer source and rate, soil properties such
as cation exchange capacity, and depth of fertilizer
incorporation.
Hauck and Stephenson (1965), working .with gran-
ular urea, found that an alkaline microenvironment
was created around each hydrolyzed urea granule, with
large granules producing pH values of 8.5 to 9.0 in the
immediate granule environment. These results are in
agreement with Volk (1959), who reported that up to
59% of the applied urea-N was volatilized on acid soil.
Ammonia volatilization is more severe under alkaline
conditions (Jewitt, 1942; Ernst and Massey, 1960;
Martin and Chapman, 1951) as would be expected
from the dissociation of NH40H. Based on a pK of
-9.28 (Lindsay, 1979), 35% of dissolved NH3 would
be in the form of NH; at pH 9, but only 0.5% at pH
7.
In an established turf, surface application of fertil-
izer is the only practical method of fertilization. The
nutrients must be solubilized and moved into the root
zone for uptake by plants. Frequently, the movement
of N into the soil may be delayed or prevented by the

SSalaries and research support provided by state and federal funds
appropriated to the Ohio Agric. Res. and Dev. Ctr., The Ohio State
Univ., Wooster, OH 44691. Journal Article no. 81-86. Received 19
June 1986.
2 Former graduate research associate, associate professor, and pro-
fessor, Agronomy Dep., The Ohio State Univ., respectively. Senior
author's present address is Tru Green, Tech. Ctr., P.O. Box 707,
Fremont, IN 46737.
Published in Agron. J. 79:535-540 (1987).