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 Title Page
 Table of Contents
 Manganese fertilization study (Dr....
 Pre- and post- emergence herbicide...
 Uniform rice nursery (Dr. Chris...
 Rice tolerance to post-emergence...
 Ratoon nitrogen study (Dr. David...
 Chemical desiccation of main crop...
 Rice cultivar evaluation (Dr. David...
 EREC rice research publications...


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/UF00054448/00005
 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: 1988
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: UF00054448:00005
 Related Items

Table of Contents
    Copyright
        Copyright
    Title Page
        Title Page
    Table of Contents
        Table of Contents
    Manganese fertilization study (Dr. George Snyder )
        Page 1
        Page 2
    Pre- and post- emergence herbicide evaluation (Dr. Joan Dusky)
        Page 3
        Page 4
    Uniform rice nursery (Dr. Chris Deren and Dr. David Jones)
        Page 5
        Page 6
    Rice tolerance to post-emergence grass herbicides (Dr. Joan Dusky and Dr. David Jones)
        Page 7
        Page 8
    Ratoon nitrogen study (Dr. David Jones )
        Page 9
        Page 10
    Chemical desiccation of main crop stubble (Dr. David Jones)
        Page 11
        Page 12
    Rice cultivar evaluation (Dr. David Jones)
        Page 13
        Page 14
        Page 15
    EREC rice research publications - 1987
        Page 16
        A field test for identifying low-Fe histosols associated with rice seedling chlorosis
            Page 17
            Page 18
            Page 19
        Seeding rate and row spacing effects on yield and yield components of drill-seeded rice
            Page 20
            Page 21
            Page 22
            Page 23
        Seeding rate and row spacing effects on yield and yield components of ratoon rice
            Page 24
            Page 25
            Page 26
        Agricultural flooding or organic soils
            Page 27
            Page 28
            Page 29
            Page 30
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








Belle Glade EREC Research Report EV-1988-2


ELEVENTH ANNUAL RICE FIELD DAY




UNIVERSITY OF FLORIDA
EVERGLADES RESEARCH AND EDUCATION CENTER
INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
COOPERATIVE EXTENSION SERVICE
BELLE GLADE, FLORIDA
JULY 11, 1988











ELEVENTH ANNUAL RICE FIELD DAY


JULY 11, 1988


EVERGLADES RESEARCH AND EDUCATION CENTER
BELLE GLADE, FLORIDA


FRANK J. COALE, PRESIDING
ASSISTANT PROFESSOR, EXTENSION AGRONOMIST


PROGRAM


8:00 -.8:30

8:30 8:45


FIELD TOUR


STOP 1


STOP 2


STOP 3


STOP 4


STOP 5


STOP 6


STOP 7


Coffee & Doughnuts

Field Tour Briefing
Dr. Frank Coale


Manganese Fertilization
Dr. George Snyder

Pre- and Post-emergence
Dr. Joan Dusky


Study


Herbicide Evaluation


Uniform Rice Nursery
Drs. Chris Deren and David Jones

Rice Tolerance to Post-emergence Grass Herbicides
Drs. Joan Dusky and David Jones

Ratoon Nitrogen Study
Dr. David Jones

Chemical Desiccation of Main Crop Stubble
Dr. David Jones

Rice Cultivar Evaluation
Dr. David Jones


APPENDIX


EREC RICE RESEARCH PUBLICATIONS 1987











MANGANESE FERTILIZATION STUDY


Dr. George Snyder
Professor
Soil Scientist



Recent investigations on preventing manganese (Mn)

deficiency of drill seeded rice on high pH organic'soils have

shown that manganese sulfate (MnSO4-H20) drilled with the seed

may be beneficial. Earlier experiments have shown grain yield

increases of 33% in plots receiving MnSO4-H20 at 60 kg/ha. The

optimum rate of Mn fertilization is not known. In this

experiment, MnSO4'H20 was drilled with Lebonnet seed at rates of

0, 20, 40, 60, 80, and 100 kg/ha. Two planting depths were used.





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PRE- AND POST-EMERGENCE HERBICIDE EVALUATION TRIAL
FOR RICE PRODUCTION IN FLORIDA

J. A. Dusky
Associate Professor, Weed Science


Objectives:

1) To determine weed control efficacy of several herbicides, alone
and in combination, particularly with respect to sprangletop,
dayflower, and alligatorweed.


2) To determine rice tolerance of several herbicides,
combination, with respect to crop vigor and yield.

Treatments:


Compound

Check
Check
Propanil
Propanil
Prowl
Prowl
Bolero
Bolero
Modown
Modown
Ordram
Ordram
Cinch
Cinch
Benchmark
Benchmark
Bas 514
Bas 514
Ordram
Ordram
Buctril
Buctril
Buctril
Basagran
Propanil + Bolero
Propanil + Modown
Propanil + Ordram
Propanil + Basagran
Propanil + Buctril
Benchmark + X-77


Rate (lb ai/A)



1.5
3.0
2.0
4.0
4.0
6.0
2.0
4.0
3.0
6.0
0.75
1.5
0.25
0.50
0.25
0.40
3.0
6.0
0.2
0.4
0.6
0.75
1.5 + 4.0
1.5 + 3.0
1.5 + 3.0
1.5 + 0.75
1.5 + 0.4
0.25 + 1 qt/A


alone and in



Time of
Application



Post
Post
Pre
Pre
Pre
Pre
Pre
Pre
Pre
Pre
Pre
Pre
Pre
Pre
Post
Post
Post
Post
Post
Post
Post
Post
Post
Post
Post
Post
Post
Post


Planted: 4-26-88 Variety: Lebonnet
Preemergence application: 4-28-88
Postemergence application: 5-24-88 Rice: 3-4 LF
Weeds: 3-4 LF


Trt #

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30


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$ 73 < 42 $

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ff~,6 Us~A;elPE ~IP\Yh`~rO~









UNIFORM RICE NURSERY (URN)


Dr. Chris Deren Dr. David Jones
Assistant Professor Associate.Professor
Plant Breeder Rice Agronomist


The Uniform Rice Nursery (URN) is an observation nursery

which is planted in Arkansas, Louisiana, Texas, Mississippi, and

California. It is made up of about 185 entries, most of which

are advanced lines from the breeding programs at Arkansas, Texas,

and Louisiana. Material from other sources (Mississippi,

California, overseas) and check varieties are also included.



This is the first year that we have planted all URN entries

here in Florida. We are hopeful that out of this material we may

identify entries which are more productive than current varieties

grown in the Everglades. Any promising selections will undergo

testing in replicated trials at various locations. Since the

composition of the URN changes yearly, new material becomes

available for observation and evaluation.






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RICE TOLERANCE TO POSTEMERGENCE GRASS HERBICIDES


J. A. Dusky and D. B. Jones
Associate Professor, Weed Science
Associate Professor, Rice Agronomy


Objectives:

1) To evaluate rice tolerance to several postemergence grass
herbicides.

2) To evaluate several postemergence grass herbicides and
their effect on rice yield.

Treatments:

Trt # Compound Rate (lb ai/A)

1 Check
2 Check
3 Fusilade 0.063
4 Fusilade 0.125
5 Fusilade 0.25
6 Poast 0.1
7 Poast 0.2
8 Poast 0.3
9 Assure 0.03
10 Assure 0.06
11 Assure 0.125
12 Select 0.075
13 Select 0.15
14 Verdict 0.125
15 Verdict 0.25
16 Lorox 1.0
17 Caparol 2.0
18 Cobra 0.25
19 Cobra 0.5
20 Whip 0.15

Planted: 4-14-88 Variety: Lebonnet


5-10-88 Rice: 3-4 LF


Application Date:
















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RATOON NITROGEN STUDY

Dr. David Jones
Associate Professor
Rice Agronomist


Despite the lack of main crop yield response to N

application of rice grown on the organic soils of the EAA, the

possibility exists that the ratoon crop may show a positive yield

response to N application after main crop harvest. The soil has

been flooded for a considerable period of time prior to the

ratoon crop, depleting the usually abundant soil N. Also, the

ratoon crop is very short duration in growth, has less vegetative

growth, and thus is more likely to respond to N application than

the main crop.

This study includes three cultivars (Gulfmont, Lebonnet, and

Lemont) and three times of N application (1, 2, and 4 weeks after

main crop harvest). The N rate used is 60 kg/ha.













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CHEMICAL DESICCATION OF MAIN CROP STUBBLE

Dr. David Jones
Associate Professor
Rice Agronomist

Ratoon crop yields have been shown to increase in response

to decreased main crop stubble height (mowing). It is assumed

that this response is, in part, related to increased light

interception by the ratoons at an early stage of growth. This

study is investigating the possibility that by chemically

desiccating the main crop stubble shortly after harvest, light

penetration through the stubble will be increased, and a yield

response may result. Applying the desiccants by aircraft would

be much more rapid and reduce wheel traffic through the field

when compared with the current practice of mowing.

This study will compare the response of two cultivars

(Gulfmont and Lebonnet) to desiccation by two chemicals (sodium

chlorate and paraquat). The control treatments will consist of

20 and 40 cm stubble heights without chemicals applied. The

treated stubble height will be 40 cm.












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RICE CULTIVAR EVALUATION

Dr. David Jones
Associate Professor
Rice Agronomist

Commercially available cultivars and advanced experimental

lines are evaluated annually to determine their performance when

grown in the unique environmental conditions and soils of the

EAA. The cultivars are evaluated in two maturity groups; very-

early and midseason-early. This year, the very-early group has

12 entries consisting of 1 private and 4 public varieties, 2

advanced experimental lines and 5 Fl hybrids. The midseason-

early group has 18 entries consisting of 3 private and 9 public

cultivars, 2 advanced experimental lines, 3 Fl hybrids and a

foreign introduction.











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APPENDIX


EREC RICE RESEARCH PUBLICATIONS 1987




Elliott, C.L. and G.H. Snyder. 1987. A field test for identifying
low-Fe Histosols associated with rice seedling chlorosis. Proc.
Soil Crop Soc. Florida 46:91-93.


Jones, D.B. and G.H. Snyder. 1987. Seeding rate and row spacing
effects on yield and yield components of drill-seeded rice.
Agron. J. 79:623-626.


Jones, D.B. and G.H. Snyder. 1987. Seeding rate and row spacing
effects on yield and yield components of ratoon rice. Agron. J.
79:627-629.


Snyder, G.H., R.H. Cherry, J.A. Dusky, J.M. Good, K.R. Reddy, and
J.O. Strandberg. 1987. Agricultural flooding of organic soils.
Florida Agric. Expt. Sta. Bulletin 870 (technical).





















Reprinted from Soil and Crop Science Society of Florida, Proceedings, Volume 46, October 14-16, 1986

A Field Test for Identifying,Low-Fe Histosols
Associated with Rice Seedling Chlorosis'
C. L. Elliott and G. H. Snyder2


ABSTRACT
A seedling-chlorosis problem of rice (Oryza sativa L) as-
sociated with low-Fe Histosols has been observed many times in
the Everglades. Chlorosis can be prevented by drilling FeSO4
with the seed at 50 to 150 Kg ha-'. Correction of chlorosis after
it develops is difficult, expensive, and uncertain. Therefore, it is
important to identify problem soils prior to seeding to determine
whether or not FeSO4 is needed at planting.
A simple, rapid method for identifying low-Fe Histosols was
developed. The procedure, based on the reaction between Fe'"
and KSCN, is suitable for field use by rice growers.
Additional index words: Organic soils, Soil testing, Oryza
sativa L., Iron chlorosis.

Rice (Oryza saliva L.) is grown on Histosols in the
Everglades Agricultural Area (EAA) in rotation with
vegetables (Snyder et al., 1977) and sugarcane (Sac-
harum sp.) (Alvarez et al., 1979). Green (1956) de-
scribed a rice-seedling-chlorosis problem in the EAA
in which "the seed germinated well, but after a week
the seedlings were unusually yellow". He observed
that the chlorosis could be prevented by applying
FeSO.I at high rates (1120 Kg ha-') prior to seeding.
The same seedling chlorosis has been observed in the
EAA many times since the resurgence of interest in
rice production during the last decade. Snyder (1981)
reported that chlorosis can be predicted prior to seed-
ing by determining the soil Fe content. The
Everglades Research and Education Center began of-
fering a soil test to Everglades rice growers to help
identify soils in which seedling chlorosis is likely to
occur. This special soil test, based on the color of
ashed soil, is offered upon request at the time soil
samples are submitted for routine fertility analysis.
Upon identification of a problem soil, chlorosis can
be prevented by drilling FeSO4 with the seed at rates
of 50 to 150 Kg ha-' (Snyder, 1982). There is no need
to drill even this relatively low amount of Fe in soils
not prone to seedling chlorosis.
Rice appears to be rather unresponsive to P and
K fertilization in the EAA (Snyder, 1980; Snyder,

'Fla. Agric. Exp. Stn. Journal Series no. 8168.
'(chemist III and Professor, respectively, Everglades Research
anid Education Center. P.O. Drawer A, Belle (lade, Fl. 33430.


1981;: Snyder and Jones, 1983; Snyder, 1985). Fur-
thermore, since rice is grown in rotation with well-fer-
tilized crops, there appears to be little reason to fer-
tilize for rice production. For these reasons, rice
growers seldom submit samples for routine soil test-
ing. Their only reason for submitting samples would
be for identifying low-Fe soils. The purpose of this
study was to develop a simple field method for iden-
tifying low-Fe Histosols associated with rice-seedling
chlorosis in the Everglades that growers themselves
could use to determine the need for drilling Fe when
planting rice.

METHODS AND MATERIALS
Surface samples (0 to 10 cm) of Histosols contain-
ing over 850 g organic matter Kg-' were collected
from nine locations in the EAA where the need for
Fe supplementation at planting is known from obser-
vation and/or experimentation by the authors. A por-
tion of each soil was retained in a field-moist condi-
tion and the remainder was dried at 60 C.
Four 20-mL screw-cap culture tubes were etched
at the 3- and 15-mL levels. A scoop of approximately
0.1-mL capacity was made by gluing a piece of plastic
tubing onto the side of a plastic stirring rod near one
end. The exact volume of the scoop is not important
since the same scoop is used for both reference and
unknown samples. The following reagents were ob-
tained or prepared: concentrated (conc) HCI, 0.5 M
KSCN (50 g L-'), and 1-butanol. A box was con-
structed to hold these supplies, a set of instructions
for the soil test, and a sample of field-moist 'Brida'
soil '(Fig. 1). The latter was collected from the Brida
Ranch of Seminole Sugar Corporation, on State Road
80 approximately 30 km east of Belle Glade, FL, Sec-
tion 35, Township 43 south, Range 39 east, in Palm
Beach County. This soil, a Terra Ceia muck (euic,
hyperthermic, Typic Medisaprists), was chosen as a
reference soil because in repeated rice plantings it
has been observed that, even though rice seedlings in
this location showed symptoms of the aforemen-
tioned seedling chlorosis, the condition was only mar-
ginally severe enough to require Fe application at









SOIL AND CROP SCIENCE SOCIETY OF FLORIDA


IKI


Fig. 1. Supplies used for identifying low-Fe Histosols; A. in-
structions, B. 'Brida' reference soil, C. calibrated culture tubes,
D. 1-butanol, E. 0.5 M KSCN, F. concentrated HCI, and G. scoop.

planting. The reference soil is maintained at field
moisture because the test is designed for field use.
Atomic absorption spectrophotometry (AAS) was
used to determine Fe in HNO3:HCIO4 digests of
oven-dry samples for the nine soils collected. In addi-
tion, 0.2 mL of cone HCI was added to 20-mg samples
of each soil, followed by 3 mL of 0.5 M KSCN. Fol-
lowing 2 min of shaking, 10 mL of 1-butanol was
added and the mixture shaken for another 30 s. Ab-
sorption at 492 nm was determined in the decanted
butanol using a double-beam spectrophotometer with
a reagent blank.


RESULTS AND DISCUSSION

The following procedure was developed for field
evaluation of the relative Fe status of Histosols in the
EAA after taking a representative sample:
Step 1. Add I scoop of soil to the calibrated cul-
ture tube.
Step 2. Add 5 drops cone HCI to the tube.
Step 3. Add 0.5 M KSCN to the etched 3-mL
mark and shake gently.
Step 4. Add 1-butanol to the 15-mL mark, screw
on the cap, and shake vigorously.
Step 5. Allow the aqueous and butanol phases to
separate.
Step 6. Observe the red color extracted into the
butanol phase.
The same procedure is used for both the unknown
and the 'Brida' reference soil. Color development in
each soil is compared. For any soil showing red color
development equal to or less than the Brida soil,
FeSO4 should be drilled with the rice seed (Fig. 2).
The cone HCI extracts Fe from the soil and
oxidizes reduced forms to the ferric state (+3). The
KSCN reacts with Fe' to form the red-colored com-
pound Fe(SCN)s. This compound dissolves into the
butanol phase, leaving most of the soil debris in the
lower aqueous phase for easier color comparison.


Fig. 2. Color development by low-Fe and 'Brida' referee
soils, and in soils in which seedling chlorosis does not occur.


1.0,


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z .4

tn
cr


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SOIL FE (G/KGI


10 12


Fig. 3. Relationship between soil Fe as determined by oxii
tive digestion/atomic absorption spectrophotometry and by a
sorbance at 492nm following HCI extraction and reaction of Ft
with KSCN.


To determine whether the test actually measure
soil Fe, a comparison was made between total soil I
measured in HNOs:HCIO4 digests using AAS and
more refined adaptation of the field procedure ;
presented in the Methods section. A correlation
(R= 0.996) was found between the two methods <
Fe determination (Fig. 3). This correlation indicate
that the proposed field test extracts and quantifies I
in Histosols of the EAA. The authors have found t!
field test for Fe in Histosols to be a quick and relial -
method for identifying soils of the EAA which r
quire Fe additions for normal rice-seedling develop
ment.

LITERATURE CITED
Alvarez, J., G. Kidder, and G. H. Snyder. 1979. The econop
potential for growing rice and sugarcane in rotation in
Everglades. Soil Crop Sci. Soc. Fla. Proc. 38:12-15.


---------~F -- mu


r I I | |


IMM








PROCEEDINGS, VOLUME 46, 1987


Green, V. E., Jr. 1956. A survey of rice culture on brganic soils.
Soil Crop Sci. So& Fli. Prdc. 16:334-351. ,
Snyder, G. H., J. Alvarez, J. W. Mishoe, D. L. Myre,;arid S. F.
Shih. 1977. The ecoromic potential foi- incdrpdratihg rice in
Everglades vegetable production system. Prdc. Fla. State Hort.
Soc. 90:3808382 ..
Snyder, G. H. 1 98. AREC- eile Glade 1979 rick research. Third
Arinual Rite Field Day, Everglades Research and Education
Center, Bell Glade, FL. p. 1-10.
Snyder, G. H. 1981. ARlP C iice research prdgrait results. Belle


Glade AREC Research Report EV-1983-3. Everglades Research
and Education Center, Belle Glade, FL. p. I-1 to I-11.
Snyder, G. H. 1982, 1981 AREC Rice Research program results.
Belle Glade AREC Research Report EV-1982-3. Everglades Re-
search and Education Center, Belle Glade, FL. p. 1-4.
Snyder, G. H., and D. B. Jones. 1983. 1982 fertility trials. Belle
Glade AREC Research Report EV-1983-6. Everglades Research
and Education Center, Belle Glade, FL. p. 1-5.
Snyder, G. H. 1985. Rice fertility research. Belle Glade EREC Re-
search Report EV-1985-7. Everglades Research and Education
Center, Belle Glade, FL. p. 21-30.







Reprinted from Agronomy Journal
Vol. 79, No. 4














Seeding Rate and Row Spacing Effects on Yield
and Yield Components of Drill-Seeded Rice'.

D. B. Jones and G. H. Snyder2


ABSTRACT
Although plant population effects on crop performance have been
thoroughly investigated In transplanted rice (Ory.a sativa L), less
Information is available for drill-seeded rice. Previous studies eval-
uating the response of rice cultivars to various seeding rates and row
spacings were performed before semi-dwarf cultivars were available
In areas where drill-seeding is practiced. Two contrasting plant types,
tall (cv. Lebonnet) and semi-dwarf (cv. Bellemont and Lemont), were
drill-seeded at rates of 50, 100, and 150 kg seed ha-' in 0.15-, 0.20-,
and 0.25-m row spacings in three tests conducted on an organic soil.
Narrow row spacings increased grain yield for both plant types when
reproductive growth occurred during a period of relatively high solar
radiation and moderate temperatures. Increased seeding rates in-
creased panicles per square meter in all tests for both plant types.
This increase was compensated for by decreased filled grain number
per panicle, resulting in no significant yield differences among seed-
ing rates. It appears that seeding rates of 80 to 100 kg ha-' are
saficient to obtain optimum stands in southern Florida.
Additional ndex words: Oryi sati L., Cultivar response, Plant-
Ing dates, Climatic productivity index, Organic soil, Histosol.

P LANT density has received considerable attention
in transplanted rice (Oryza sativa L.). Yamada
(1961) reviewed results of spacing studies conducted
on transplanted rice in Japan, and concluded that in
general, higher planting density produced more total
dry matter and grain per unit area when rice was grown
on less-fertilized land. Chandler (1969) stated that the
problems of spacing are closely related to the mor-
phological characteristics of the rice plant, particularly
to such features as tillering capacity and leaf and tiller
erectness, factors that are related to N response. Tan-
aka et al. (1964) found that the optimum spacing at a
low N level is closer than at a high N level, but op-
timum spacing was wider in the rainy season than in
the dry season.
Agronomic factors such as plant height and maturity
also affect optimum plant spacing in transplanted rice.

Contribution from the Univ. of Florida Inst. of Food and Agric.
Sciences. Florida Agric. Exp. Stn. Journal Series no. 7698. Received
18 Sept. 1986.
SAssistant professor and professor, Everlades Res. and Educa-
tion Ctr., P.O. Drawer A, Belle Glade, FL 33430.
Published in Agron. J. 79:623-626(1987).


Intermediate or tall cultivars tend to lodge at close
spacing, while short and lodging-resistant varieties give
the highest yield at close plant spacing (Tanaka et al.,
1964). Close spacing is essential for early maturing
cultivars to achieve high yields because insufficient
vegetative growth prevents them from achieving max-
imum yields at more conventional spacings (Yoshida,
1978).
In contrast to transplanted rice where spacing be-
tween plants is equidistant, mechanically planted rice
is placed in discrete rows. Thus, interplant competi-
tion varies greatly when seeding rate or row spacing
is altered. In wider row spacings more seeds must be
planted per unit of row to achieve a particular density,
thus increasing interplant competition within the row.
Although little data are available to support an opti-
mum spacing for drill-seeded rice, 0.18 m is generally
used in the United States. Scott (1965) found that rice
grown in 0.23- and 0.46-m rows had similar yields.
The number of tillers per area was reduced in the 0.46-
m row spacing, but a corresponding increase in panicle
weight compensated for the reduced tiller number. Ev-
att (1967, 1968) later found that yields from 0.10-m
rows were higher than those from 0.20-m rows, but
the yield advantage varied over years.
Currently, recommended seeding rates range from
90 to 112 kg ha-' (Huey, 1984). In early studies it was
reported that a broad range of seeding rates produced
satifactory yields (Nelson, 1931). More recent studies
conducted in Arkansas (Faw and Porter, 1981) found
that, for a given cultivar, as the number of panicles
per square meter increased, the number of grains per
panicle decreased, while 1000-grain weight remained
constant. This compensation effectively provided a
maximum grain yield independent of panicle popu-
lation within a relatively wide range of seeding rates.
The authors concluded that the competitive effects of
dense stands were harmful during or prior to panicle
development. Wells and Faw (1978) found no yield
differences between seeding rates at low N levels, but
lower seeding rates had significantly higher yields at
high N levels. They concluded that under high N fer-
tility the adverse effects of excessive vegetative growth








AGRONOMY JOURNAL. VOL. 79. JULY-AUGUST 1987


before anthesis limited grain yields under dense pop-
ulations.
Commercial rice production has recently begun in
the subtropical climate of the Everglades Agricultural
Area (EAA) of southern Florida where production is
entirely on Histosols. Since considerable N is miner-
alized in drained Histosols (Tate, 1976), no fertilizer
N is currently used by rice growers in the EAA. The
predominant cultivar grown in the area is Lebonnet
(Bollich et al., 1975), a tall, early maturity cultivar.
With the recent release of early maturing, semi-dwarf
cultivars (Bollich et al., 1983; 1985), semi-dwarf cul-
tivars can be expected to replace tall cultivars in the
near future.
Very little data exist on the effects of row spacing
on drill-seeded rice. There has been considerably more
attention paid to seeding rate effects, but the results
have been variable, possibly due to varying fertility
and environmental conditions under which the ex-
periments have been conducted. No studies have in-
vestigated the response of the erect-growing, semi-dwarf
cultivars to varying seeding rates and row spacings
since they have only recently been introduced to areas
of the United States where drill-seeding is practiced.
The objective of this study was to measure the yield
and yield component responses of a traditional tall and
Table 1. Rice grain yield as affected by row spacing and seeding
rate for two contrasting plant types.
Tall type Semi-dwarf type
Treatment
Row Seeding Testt Test
spacing rate EP IP LP EP IP LP
m kg ha"' Mg ha'---
0.15 6.66 5.47 3.74 6.37 5.21 4.98
0.20 6.41 5.69 3.81 6.04 5.90 .5.00
0.25 5.86 5.44 3.92 5.51 5.72 5.20
50 6.40 5.09 3.88 6.25 5.69 4.85
100 6.16 5.60 3.87 5.90 5.54 5.28
S 150 6.37 5.81 3.72 5.77 5.61 5.05
Mean 6.31 5.50 3.83 5.97 5.61 5.06
LSD,.,. Treatment 0.59 NS NS 0.55 NS NS
LSDo." Test 0.37 0.29
F value
Row spacing (RS) 3.9* 0.INS 0.4NS 5.3** 3.1NS 0.9NS
Seeding rate (SR) 0.4NS 1.5NS 0.4NS 1.8NS 0.1NS 2.9NS
RS x SR 0.9NS 0.6NS 1.ONS 1.2NS 2.2NS .0.4NS
*,** Indicate significance at the 0.05 and 0.01 levels, respectively; NS =
not significant.
t EP = early planting: IP = intermediate planting: and LP = late
planting.

Table 2. Average values for daily total solar radiation and daily
mean air temperature 25 days prior to flowering and climatic
productivity index for three tests.
Daily total solar Daily mean air climatic productivity
Test radiation temperature index*
MJ m" "C
EP 20.0 26.0 9.4
IP 19.9 27.3 8.5
LP 17.6 26.4 8.0
t Calculation utilizes calories cm"'.
t Climatic productivity index = S (278 7.07t) x FPG x MGW x 10-',
where S = average daily total solar radiation 25 days prior to flowering;
t = average daily mean air temperature 25 days prior to flowering; FGP
= filled grain percent; and MGW = 1000-grain weight.
I EP = early planting; IP = intermediate planting; and LP = late planting.


a semi-dwarf plant type to varying seeding rates and
row spacings.

MATERIALS AND METHODS
Tests were conducted at the Everglades Research and Ed-
ucation Center (EREC) at Belle Glade, FL, in 1982 and 1985.
In each test, the soil (Pahokee muck, a Euic, hyperthermic
Lithic Medisaprist) was fertilized with P, K, and micronu-
trients according to the EREC soil test recommendations
(Shuler et al., 1981). Following fertilizer incorporation by
rototilling, the plot area was rolled to prepare a firm seedbed.
Plots were drill-seeded on 19 Mar. 1982 (early planting) and
S11 Apr. (intermediate planting) and 20 May 1985 (late plant-
ing).
Plots were seeded with either tall or semi-dwarf cultivars
at rates of 50, 100, and 150 kg ha in row spacings of 0.15,
0.20. and 0.25 m in all possible combinations. Lebonnet
(Bollich et al., 1975) represented the tall plant type, and
'Bellemont' (Bollich et al. 1983) (1982 test) and 'Lemont'
(Bollich et il., 1985) (1985 tests) represented the semi-dwarf
plant type. Randomized complete block designs with five
replications were used in the three tests. Individual plots
consisted of six rows, 5 m in length. Plant populations were
determined 2 to 3 weeks after planting by counting the num-
ber of plants in I-m lengths of row from two rows in the
center of each plot. The plots were flooded 3 to 5 weeks after
seedling emergence when the rice plants were sufficiently tall
to remain above the floodwater. Propanil [N-(3,4-dichloro-
phenyl)propanamide] at 2.2 kg ha was applied prior to
flooding to control weeds.
At harvest, the plots were drained and the I-m lengths of
row utilized for seedling counts were hand harvested for
yield and yield component determination. The grain was
threshed, weighed, and evaluated for moisture by electrical
resistance. Grain yields were recorded as rough rice at 120
g kg moisture. Three 100-grain subsamples were taken from
the harvested grain of each plot to determine 1000-grain
weight. Grain number per panicle was calculated by dividing
the grain weight per plot by panicle number per plot and
weight per grain. Data were statistically evaluated by analysis
of variance using the SAS data processing package (SAS In-
stitute, 1982).
Daily minimum and maximum air temperature and solar
radiation were recorded throughout the course of the tests
at the EREC weather station (Allen, 1983: Schwandes, 1986),
located approximately 0.6 km from the plots.
The climatic productivity index (CPI), an estimate of yield
based on average daily total solar radiation and mean air
temperature of the 25-day period prior to flowering (Yoshida
and Parao, 1976), was calculated for each experiment by the
following formula:
CPI = S(278 7.07t) X FGP X MGW X 10-5,
where S = average daily total solar radiation (measurements
in MJ m-', calculated using cal cm-'), t average daily
mean air temperature (OC), FGP = filled-grain percent, and
MGW 1000-grain weight.

RESULTS AND DISCUSSION
Grain yields differed significantly (P<0.05) among
tests, being highest in the early planting (EP) and low-
Sest in the late planting (LP) for both plant types (Table
1). Differences among tests likely reflect yield re-
sponses to:different planting dates and, thus, differing
environments during plant growth and development.
Similar responses to planting dates in southern Florida
have been demonstrated by Snyder (1980).
Since the row spacing (RS) X seedipg rate (SR) in-







JONES & SNYDER: SEEDING RATE & ROW SPACING EFFECTS ON DRILL-SEEDED RICE


teraction was not significant (P<0.05), the main effects
of RS and SR on grain yield can be examined (Table
1). Yields of both plant types in the EP were signifi-
cantly increased with decreasing RS. The lack of a
significant grain yield responses to spacing in the in-
termediateplanting (IP) and LP may have resulted
from either lower'solar radiation, higher air temper-
ature, or a combination of both that occurred during
these two tests. Tanaka et al. (1964) found similar re-
sponses to spacing of transplanted rice in Asia during
high (dry season) and low (wet season) yield environ-
ments. They concluded that optimum spacings were
narrower in high yield environments. Yoshida and
Parao (1976) determined that potential grain yield of
rice for a particular environment was positively related
to average daily total solar radiation and negatively
related to average daily mean air temperature during
the reproductive period of growth, which begins 25
days prior to flowering. When the CPI was calculated
for the IP and LP. their potential productivity was only
90 and 85% that of the EP, respectively (Table 2).
The number of seedlings per square meter (SMS)
was significantly increased by increasing seeding rates
for both cultivars (Table 3). The overall mean seedling
populations for 50, 100, and 150 kg ha seeding rates
were 136, 256, and 372 SMS, respectively. Huey (1984)
suggests that optimum seedling stands for direct-seeded
rice range from 160 to 215 SMS. It appears that seeding
rates of 80 to 100 kg ha are sufficient to obtain op-
timum stands in southern Florida. Spacing had little
effect on seedling population (Table 3). An interaction
was found between RS and SR for the semi-dwarf plant
type in the LP. Although SMS increased with increased
SR at all RS, the magnitude of the increase varied,
resulting in the interaction. Spacing effects of SMS were
relatively small in magnitude when compared to SR
effects and would be of little practical significance un-
der field conditions.
Rice grain yields are a function of panicles per square
meter (PMS), filled grain number per panicle (GNP),
and 1000-grain weight (MGW). Spacing only signifi-
cantly (P<0.05) affected a yieldcomponent on one
occasion (tall plant type, LP) where GNP was higher
at the 0.20-m RS (47GNP) than at 0.15 or 0.25-m RS
(both 41GNP); therefore, yield component data were
combined over spacings for the three tests (Table 4).
Panicles per square meter were significantly (P<0.01)
increased by increasing seeding rates in all tests for
both plant types. Panicles per square meter were in-


creased 61 and 50% between 50 and 150 kg ha -' seed-
ing rates for the tall and semi-dwarf plant types, re-
spectively. In drill-seeded rice, PMS is largely
dependent on seeding rate and percentage of emer-
gence, factors that determine SMS. There was a 41%
difference in mean PMS between tests for both plant
types. Differences for SMS between tests were 40 and
66% for the tall and semi-dwarf plant types, respec-
tively. Thus it appears that differences between tests
for PMS were directly related to SMS differences for
the tall plant type. Differences for the semi-dwarf could
be accounted for by a combination of differences in
SMS and increased tillering that compensated for the
lower SMS. This latter case can be shown by consid-
ering the number of panicles per seedling. The average
number of panicles per seedling for the tall and semi-
dwarf plant types was similar over tests, being 1.42
and 1.51, respectively. Yet in the IP, where the semi-
dwarf had lower SMS than the tall plant type (170 vs.
214, Table 3), it had higher panicles per seedling values
(1.69 vs. 1.41). Although various factors may affect
seedling survival and thus SMS, tillering appears to
compensate for such differences.

Table 3. Seedling number per square meter as affected by row spac-
ing and seeding rate for two contrasting plant types.
Tall type Semi-dwarf type
Treatment
Testt Test
Row Seeding ---
spacing rate EP IP LP. EP IP LP Mean
m kg ha --no. m'"
0.15 302 212 267 278 177 252 248
0.20 -- 361 222 240 299 170 212 251
0.25 305 209 303 271 162 277 256
50 164 104 154 145 98 153 136
100 328 221 274 281 179 259 256
150 467 313 382 421 313 337 372
Mean 323 214 270 283 170 247 251
LSD,,, Treat-
ment 51 26 31 49 23 38
LSD... Test 21 21
F value
Row spacing
(RS) 3.5* 0.6NS 8.6** 0.8NS 0.8NS 6.2**
Seeding rate
(SR) 77.4** 140.7** 112.2** 67.2** 72.5** 47.9*
RS x SR 1.2NS 1.4NS 2.6NS 0.7NS 0.SNS 2.8*
*** Indicate significance at the 0.05 and 0.01 levels, respectively; NS =
not significant.
t EP = early planting; IP = intermediate planting; and LP = late
planting.


Table 4. Effect of three seeding rates on yield components of two contrasting plant types.
Tall type Semi-dwarf type
Panicles Filled grain Grain weight Panicles Filled grain Grain weight
Testt Test Test Test Test Test
Seeding rate EP IP LP EP IP LP EP IP LP EP IP LP EP IP LP EP IP LP
kg ha-' no. m-' no. panicle" g 1000- no. rm' no. panicle" g 1000' -
50 222 203 315 123 96 52 23.5 26.5 24.0 232 221 272 119 97 68 22.7 26.4 26.4
100 310 280 415 85 77 39 23.4 26.1 23.5 311 264 389 83 79 54 22.8 26.4 25.3
150 403 347 440 67 66 37 23.6 25.9 22.7 357 294 466 74 73 43 22.3 26.0 25.0
Mean 312 277 391 92 80 43 23.5 26.2 23.4 301 260 376 92 84 56 22.7 26.3' 25.6
LSDo. Treatment 36 49 42 12 12 5 NS* NS 0.6 38 33 42 11 6 8 NS NS 0.5
LSDo.. Test 24 6 0.3 21 5 0.3
t EP = early planting; IP = intermediate planting: and LP = late planting. NS = not significant at the 0.05 level







AGRONOMY JOURNAL, VOL 79, JULY-AUGUST 1987


Grain number per panicle significantly (P< 0.01) de-
creased with increasing seedingrates for both plant
types in all tests (Table 4). The effect of seeding rate
on GNP can be explained by yield component com-
pensation between PMS and GNP. Grain number per
panicle was found to be related to PMS as:
GNP = 148.7 -0.23 PMS (r2 0.99).
Compensation between GNP and PMS over seeding
rates of drill-seeded rice has been reported by others
(Wells and Faw, 1978; Faw and Porter, 1981).
The MGW of rice is a relatively stable varietal char-
acter because the grain size is rigidly controlled by the
size of the hull. In the present studies, the MGW re-
mained fairly constant over seeding rates although there
was a tendency for MGW to decrease as seeding rate
increased (Table 4). In the LP there was a significant
(P<0.01) decrease in MGW for both plant types as
seeding rate increased. Yoshida and Parao (1976) con-
ducted shading studies at different growth stages and
found. that shading at both the reproductive and rip-
ening stages reduced MGW. It thus appears that low
solar radiation during these growth periods in the LP
(Table 2) in conjunction with higher plant popula-
tions, singularly or combined, significantly reduced
MGW in this experiment.

SUMMARY
Changes in yield and yield components over various
seeding rates and row spacings were similar for tall
and semi-dwarf plants types. Narrow row spacings sig-
nificantly increased grain yields for both plant types
when reproductive growth occurred during a period of
relatively high solar radiation and moderate temper-
atures. Under less favorable climatic conditions, grain
yields were lower and yield component compensation
stablized yields over the range of seeding rates and
row spacings investigated.

ACKNOWLEDGMENTS
The authors wish to express their appreciation to Ms.
Theresa Sanford and Mr. Linwood Johnson for their assis-
tance in the field and laboratory, and to Mr. Norman Har-
rison for his assistance with the data processing.


REFERENCES
Alien, R.J., Jr. 1983. 1982 Climatological report. Univ. of Florida
Belle Glade AREC Res. Rep, EV-1983-4.
Bollich, C.N., B.D. Webb, M.A. Marchetti, and J.E. Scott. 1983.
'Bellemont' rice. Crop Sci. 23:803-804.
and --- 1985. Registration of'Lemont'
rice. Crop Sci. 25:883-885.
S-- J.E. Scott, and J.G. Atkins. 1975. Registration of
'Leboniet' rice. Crop Sci. 15:886.
Chandler, R.F., Jr. 1969. Plant morphology and stand geometry in
relation in nitrogen. p. 265-289. in J.D. Eastin et al. (ed.) Phys-
iological aspects of crop yield. American Society of Agronomy
and Crop Science Society of America, Madison, WI.
Evatt, N.S. 1967. Rice soils and fertilizer studies. Rice J. 70(7): 84-
86.
- 1968. Rice fertilizer studies. Rice J. 71(7):32,34,36.
Faw, W.F., and T.K. Porter. 1981. Effect of seeding rate on per-
formance of rice varieties. Univ. of.Arkansas Agric. Exp. Stn.
Mimeo Ser. 287.
Huey. B.A. 1984. Seeding. p. 8-12. In Rice production handbook.
University of Arkansas Coop. Ext. Ser. MP 192.
Nelson, M. 1931. Preliminary report on cultural and fertilizer ex-
periments with rice in Arkansas. Arkansas Agric. Exp. Stn. Bull.
264.
SAS Institute. 1982. SAS user's guide: Statistics. 1982 ed. SAS In-
stitute, Cary, NC. : '
Schwandes, L. 1986. 1985 Climatological report. Univ. of Florida
Belle Glade EREC Res. Rep. EV-1986-1.
Scott, J.E. 1965. Effects of row spacing, seeding rate and high ni-
trogen fertilization on rice yields. p. 28-29. In Proc. 10th Rice
Tech. Working Group, Davis, CA. 17-19 June 1964. USDA-ARS,
Washington, DC.
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. 1980. AREC-Belle Glade 1979 rice research, p. 1-10.
In Third annual rice field day. Agricultural Research and Edu-
cation Center, Belle Glade, FL.
Tanaka, A., S.A. Navasero, C.V. Garcia, F.T. Parao, and E. Ramirez.
1964. Growth habit of the rice plant in the tropics and it. e'-ct
on nitrogen response. Tech. Bull. 3. International Rice ic-.:vch
Institute, Los Bailos, Philippines.
Tate, R.L III. 1976. Nitrification in Everglades Histosc'r: en A -
tial role in soil subsidence. Int. Assoc. Hydrolo;:::. '..i. i'c.
Anaheim Symp. 121:657-663.
Wells, B.R., and W.F. Faw. 1978. Short-statured rie e;.:;- to
seeding and N rates. Agron. J. 70:477-480.
Yamada, N. 1961. On the relationship between yikid -n. spocing
in rice. Agric. Hortic. 36:13-18, 311-316.
Yoshida, S. 1978. Tropical climate and its influence on rice. IRRI
Res. Pap. Ser. 20. International Rice Research Institute, Los Bailos,
Phillippines.
and F.T. Parao. 1976. Climatic influence on yield and yield
components of lowland rice in the trold~-s. p. 47:-.-~4'In. Clir.ate
and rice. International Rice Research Institute, Los efaios, Phil-
ippines.






Reprinted from Agronomy Journal
Vol. 79, No. 4

Seeding Rate and Row Spacing Effects on Yield and Yield Components of Ratoon Rice*

D. B. Jones and G. H. Snyder2


ABSTRACT
Ratoon cropping of rice (Oryra satire L.) has recently received
renewed attention as a means to lower unit production costs. How-
ever, little information Is available on the effect of main crop cultural
practices on ratoon yields of drill-seeded rice. The objective of this
study was to determine the effect of main crop seeding rate and row
spacing of drill-seeded rice on yield and yield components of the
ratoon crop. Two contrasting plant types, tall (cv. Lebonnet) and
semi-dwarf (cv. Bellemont and Lemont), were drill-seeded at rates
of 50, 100, and 150 kg seed ha in 0.15-, 0.20-, and 0.25-m row
spacings In three tests conducted on an organic soil. Ratoon grain
yields differed significantly (P<0.01) among tests for both plant
types, and were not significantly (P<0.05) correlated to main crop
grain yields (r- -0.62). Ratoon grain yields of both cultivars were
not significantly (P<0.05) affected by main crop seeding rate, row
spacing, or seeding rate X row spacing interaction. Increased seeding
rates significantly increased ratoon panicles per square meter (P<
0.01) and decreased ratoon filled grain number per panicle (P<0.01)
in all tests for both plant types. Panicles per square meter and filled
grain number per panicle accounted for over 85% of the variation in
ratoon grain yield. Compensation between these two yield compo-
nents stabilized ratoon grain yield at relatively low levels.
Additional index words Oryza satire L., Cultivar response, Drill-
seeding, Yield component analysis, Organic soil, Histosol, Stubble-
crop, Second crop.

R ATOON cropping is the practice of obtaining a sec-
S ond crop from the stubble of a harvested crop
(main crop). Ratooning of rice (Oryza sativa L.) is
practiced in several countries (Plucknett et al., 1970;
Chauhan et al., 1985). In the Gulf Coast areas of the
United States, rice ratooning has been practiced since
the early 1960s. Ratooning has several advantages: low
production cost, high water-use efficiency, and a re-
duced growth duration. Yet, since ratoon grain yields
are low and grain quality is generally inferior to that
of the main crop (Webb et al., 1975), ratooning has
only been used on a limited commercial basis. Due to
the recent introduction of early maturing rice cultivars
with good ratooning ability, ratooning is receiving re-
newed attention as a way to lower unit production
costs since it is possible to harvest two crops in areas
where the growing season is'too short to obtain two
planted crops.
Information on the effects of main crop cultural
practices on .ratoon yield are few and are primarily
limited to transplanted rice (Chauhan et al., 1985).
Main crop plant population may be an important fac-
tor influencing ratoon performance since ratoon tillers
arise from dormant buds of main crop tillers. High
main crop plant populations increase tiller number per
unit area (Faw and Porter, 1981; Wells and Faw, 1978),
thus increasing potential ratoon tiller number per unit
area. However, increasing main crop tiller number with
higher main crop plant populations may not give a
proportional increase in ratoon population (Bahar and

Contribution from the Univ. of Florida Inst. of Food and Agric.
Sciences. Florida Agric. Exp. Stn. Journal Series no. 7697. Received
20 Oct. 1986.
3 Assistant professor and professor, Everglades Res. and Educa-
tion Ctr., P.O. Drawer A, Belle Glade; Fl 33430.
Published in Agron. J. 79:627-629 (1987).


DeDatta, 1977). Bahar and DeDatta (1977) found that
0.20- by 0.20-m spacing in transplanted rice produced
optimum ratoon grain yields. However, in another re-
port, 0.10- by 0.10-m plant spacing gave significantly
higher ratoon grain yields than did 0.20- by 0.20-, 0.30-
by 0.30-, or 0.40- by 0.40-m spacings (Altamarino,
1959). 'No such information is available for drill-seeded
rice.
The objective of our study was to determine the
effect of main crop seeding rate and row spacing of
drill-seeded rice on yield and yield. components of the
ratoon crop of a tall and a semi-dwarf plant type.

MATERIALS AND METHODS
Tests were conducted at the Everglades Research and Ed-
uctation Center (EREC) at Belle Glade, FL, in 1982 and
1985. on Pahokee muck (a Euic, hyperthermic Lithic Med-
isaprist). Experimental treatments and main crop responses
were reported by Jones and Snyder (1987). After main crop
harvest, the plots were mowed to a stubble height of 0.20 to
0.25 m and were reflooded 3 to 5 days after mowing. At
ratoon grain ripening, the field was drained and plots were
hand harvested as in the previous study (Jones and Synder,
1987).
Harvested panicles were counted, the grain was threshed,
weighed, and corrected for moisture, and plot yields were
recorded as rough rice at 120 g kg-' moisture. Three 100-
grain subsamples were taken from the harvested grain of
each plot to determine 1000-grain weight. Grain number per
panicle was calculated by dividing the plot weight by panicle
number per plot and 1000-grain weight. Data were statisti-
cally evaluated using the SAS data processing package (SAS
Institute, 1982). R-square analysis (SAS Institute 1982) was
used to determine the relative contribution of ratoon yield
components to ratoon grain yield.

RESULTS AND DISCUSSION
Ratoon crop (RC) grain yields differed significantly
(P<0.01) among tests for both tall and semi-dwarf
plant types (Table 1). Both plant types had the highest
ratoon grain yields in the late planting (LP), but yield
rankings were different in the other two test, with the
tall plant type having the next highest yield in the early
planting (EP), while the semi-dwarf plant type had the
next highest yield in the intermediate planting (IP).
Ratoon crop grain yields were not significantly (P<
0.05) correlated to main crop (MC) grain yields over
experiments and plant types (r= -0.62). Although
some studies have found significant positive correla-
tions between ratoon and main crop yields, most have
not (Chauhan et al., 1985). This lack of association
between the yield of the two crops is understandable
since ratooning ability is a complex interaction of ge-
netic, climatic, and management variables.
Main crop row spacing (RS), seeding rate (SR), and
their interaction had no significant effect (P<0.05) on
RC grain yields (Table 1). Close spacing is essential
for high grain yields of early maturing cultivars be-
cause insufficient vegetative growth can limit yield at
conventional plant spacings (Yoshida, 1978). Rice ra-
toons have very short growth durations, reaching ma-







AGRONOMY JOURNAL, VOL. 79. JULY-AUGUST 1987


Table 1. Ratoon grain yield as affected by main crop row spacing
and seeding rate in three tests.
Tall type Semi dwarf type
Testt Test
Row Seeding Test
spacing rate EP IP LP EP IP LP


m kg ha-------- Mg ha-'
0.15 3.92 2.96 4.34 2.68 3.49 4.08
0.20 3.74 2.95 4.51 2.52 3.53 3.95
0.25 3.78 3.05 4.28 2.58 3.74 4.18
50 4.05 3.05 4.62 2.62 3.54 4.20
- : 100 3:62' 2.96 4.22 2.69 3.39 4.18
150 3.76 2.96 4.28 2.47 3.84 3.83
Average
Ratoon crop (RC) 3.81 2.99 4.37 2.59 3.59 4.07
Main crop 6.31 5.50 3.83' 5.97 5.61 5.06


Total 10.12
LSD,.. Test-RC


8.20 8.56. 9.20
0.25


9.13


F- Value
Row spacing (RS) 0.2$ 0.1 0.4 0.3 0.3 0.6
Seeding rate (SR) 1.1: 01 1. 0.6 ; 2.1 1.7
RS x SR 0.5 0.4 0.5 0.4 0.5 0.5
t EP = early planting; IP = intermediate planting; and LP = late planting.
: All F values were not significant at the 0.05 level of probability.

turity in only 35 to 60% of the time required for the
MC (Jones, 1985; Karunakaran et al., 1983). There-
fore, it would be. expected that ratoon crop yields would
be increased by narrower row spacings. Yet, the row
spacings investigated in these studies had no signifi-
cant effect (P<0.05) on ratoon yield or yield compo-
nents. This lack of ratoon response to narrow RS re-
quires further study.
The main effects of RS and SR on yield components
over tests are presented in Table 2. Only one signifi-
cant interaction was observed between a test and a
yield component (semi-dwarf plant type, 1000-grain
weight; test X RS X SR; P<0.05). Since the 1000-
grain weight contribution to yield variation was rel-
atively small when compared to the other yield com-
ponents (to be discussed later), the data showing the
interaction were omitted.
Seeding rate significantly (P<0.01) affected the ratio
of RC panicles to MC panicles for both plant types
(Table 2). As SR increased, the RC/MC panicle ratio


Decreased :indicating that ht higher MC populations,
MC panicles give rise to fewer RC panicles. This re-
duction in the average number of RC panicles pro-
duced per MC panicle was offset by increased MC
plant populations, thus resulting in significantly (P<
0.01) higher RC panicle number per square meter at
higher SR for both plant types (Table 2).
There was a significant (P-<0.01) decrease in RC
grain number per panicle as SR increased for both
plant types (Table 2). This response of RC grain num-
ber per panicle appears to be associated with increased
panicle number per square meter at higher SR. Grain
number per panicle was negatively (P<0.01) corre-
lated with panicle number per square meter (r= -0.97).
Similar yield component compensation between grain
number per panicle and panicle number per square
meter has been reported in the MC (Faw and Porter,
1981; Jones and Snyder, 1987; Wells and Faw, 1978).
One-thousand-grain weight was not significantly af-
fected by SR, although there was a significant (P<
0.05) interaction of RS X SR on 1000-grain weight of
the semi-dwarf plant type. Since differences in 1000-
grain weight over treatments were relatively small (<
2%) compared to differences in the other two yield
components (>20%), this interaction has little prac-
tical significance. Therefore, it appears that yield com-
ponent compensation between RC panicle number per
square meter and grain number per panicle is respon-
sible for the lack of RC yield response to SR.
For the linear regression ofgrain yield against yield
components, panicle number per square meter (PMS)
had the highest coefficient of determination (r2 0.34)
of the individual RC yield.components (Table 3). Us-
ing R-square analysis (SAS Institute, 1982) to deter-
mine the relative contribution of the yield components
to ratoon grain yield, the addition of grain number per
panicle (GNP) to PMS improved the coefficient of de-
termination considerably (R2=0.85)., The addition of
the third yield component, 1000-grain weight (MGW),
only improved the coefficient slightly (RI 0.89), in-
dicating that MGW is the least significant of the three
Components. The further addition of two other factors,
test and plant type, gave no further improvement in
the coefficient.' Rateon yield was found to be related


Table 2. Effect of main crop row spacing and seeding rate on ratoon yield components of two plant types.
Tall type ; Semi-dwarf type
RC/MC panicle Filled grain 1000-grain RC/MC Filled grain 1000-grain
Row spacing Seeding rate ratiot Panicles m-' panicle-1 weight panicle ratio Panicles m" panicle' weight
m kg ha-' no. --- g no. -- g
0.15 1.8 576 29 22.8 1.4 425 38 22.3
0.20 1.8 570 30 22.8 1.3 420 37 22.4
0.25 1.6 :523 32 22.9 1.4 417 37 22.7
S50 1.9 483 36 22.9 1.5 373 42 22.5
-100 1.7 576 28 23.0 1.3 426 37 22.6
S150 1.5 610 27 22.6 1.2 463 33 22.3
Average 1.8 557 31 22.9 1.4 421 37 22.5
LSD... 0.2 47 3 NS 0.1 29 3 NS
F Value
Row spacing (RS) 2.5 NS 3.1 NS 2.3 NS 0.7 NS 0.9 NS 0.1 NS 0.1 NS 2.4 NS
Seeding rate (SR) 7.6 ** 15.6 ** 27.1 ** 2.6 NS 10.0 ** 19.3 ** 22.9 1.2 NS
RS x SR 0.8 NS 0.9 NS 0.3 NS 2.4 NS NS 1. S .16 .NS 1.5 NS 2.6*
*.** Indicate significance at the 0.05 and 0.01 levels, respectively; NS = not significant.
t Ratoon crop panicles per main crop panicle.










Table 3. The coefficient of determination for various factors con-
tributing to ratoon grain yield.
Factor r.i R'
Panicles m-' (PMS) 0.34
PMS + Grain number panicle-' (GNPI 0.85
PMS + GNP + 1000-grain weight (MGW) 0.89
PMS + GNP + MGW + Test 0.89
PMS + GNP + MGW + Test + Plant type 0.89


to PMS and GNP as: RC yield = -114.28 + 0.52
PMS + 16.56 GNP + 0.18 PMS X GNP (R2= 0.93).
Thus, it appears PMS, GNP, and their interaction
(compensation) are the primary determinants of ra-
toon yield.

SUMMARY
Tall and semi-dwarf plant types responded similarly
to SR and RS. Seeding rate, RS, and their interaction
had no significant effect on RC yield. Row spacing had
no effect on RC yield components, while increasing
SR increased RC PMS and decreased RC GNP. Ra-
toon crop PMS and GNP were the primary compo-
nents of RC yield, but compensation between the two
components stabilized RC yields at low levels.

ACKNOWLEDGMENTS
The authors wish to express their appreciation to Ms.
Theresa Sanford and Mr. Linwood Johnson for their assis-


tance in the field and laboratory, and to Mr. Norman Har-
rison for his assistance with the data processing.

REFERENCES
Altamarino, L. 1959. The influence of spacing on the development,
yield and agronomic characters of rice ratoon crop. M.S. thesis.
Univ. of the Philippines at Los Bailos, Laguna, Philippines.
Bahar, F.A., and S.K. DeDatta. 1977. Prospects of increasing trop-
ical rice production through ratooning. Agron. J. 69:536-540.
Chauhan, J.S., B.S. Vergara, and F.S.S. Lopez. 1985. Rice ratooning.
IRRI Res. Pap. Ser. 102 International Rice Research Institute,
Los Baflos, Philippines.
Faw, W.F., and T.K. Porter. 1981. Effect of seeding rate on per-
formance of rice varieties. Univ. Arkansas Agric. Exp. Stn. Mimeo
Ser. 287.
Jones, D.B. 1985. The effect of plant crop cutting height on ratoon
crop agronomic performance and yield. Univ. of Florida Belle
Glade EREC Res. Rep. EV-1985-7.
---, and G.H. Snyder. 1987. Seeding rate and row spacing effects
on yield and yield components of drill-seeded rice. Agron. J.
79:623-626.
Karunakaran, K., M.B. Jalajakumari, and P. Sreedevi. 1983. Ratoon
performance of some short duration rice cultures. Int. Rice Res.
Inst. Newl. 8(4):4.
Plucknett, D.L., J.P. Everson, and F.W. Sanford. 1970. Ratoon crop-
ping. Adv. Agron. 22:285-331.
SAS Institute. 1982. SAS user's guide: Statistics. 1982 ed. SAS In-
stitute, Inc., Cary, NC.
Webb, B.D., C.N. Bollich, and J.E. Scott. 1975. Comparative quality
characteristics of rice from first and ratoon crops. Texas Agric.
Exp. Stn. Prog. Rep. 3324C.
Wells, B.R., and W.F. Faw. 1978. Short-statured rice response to
seeding and N rates. Agron. J. 70:477-480.
Yoshida, S. 1978. Tropical climate and its influence on rice. IRRI
Res. Pap. Ser. 20. International Rice Research Institute, Los Baftos,
Phillippines.













Bulletin 870 (technical)


Agricultural Flooding
of Organic Soils


G. H. Snyder, Editor


Agricultural Experiment Station
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
J. M. Davidson, Dean for Research


August 1987





















ABSTRACT


Flooding drastically alters the chemistry and biology of organic
soils, primarily because of greatly reduced availability of oxygen in
the soil for chemical and biological processes. Flooding decreases
microbial oxidation of soil organic matter and reduces associated
conversion of organically bound nitrogen to plant available forms.
Flooding increases solubility, and therefore plant availability, of
phosphorus, iron, and manganese. Soil pH generally increases as a
result of flooding, and remains elevated for some time after flooding is
completed. When the flood is removed, availability of phosphorus and
of certain micronutrients such as iron, manganese, and zinc, may be
reduced by the elevated soil pH.
Populations of a number of soil insects are reduced by properly
timed flooding of suitable duration. Flooding is routinely used to
control nematodes, particularly in vegetable production systems.
Some plant pathogens, mainly fungi, are controlled by flooding, espe-
cially during warm periods. Growth of most terrestrial weeds is
suppressed by flooding, although many weeds reestablish soon after
the flood is removed.
By properly understanding the effect of flooding on properties of
organic soils, flooding can be a valuable management tool for crop
production.




















TABLE OF CONTENTS


Chapter 1
Introduction: Flooding as a management practice in the
Everglades Agricultural Area................................ 1
G. H. Snyder

Chapter 2
The effect of flooding on physical, chemical, and
microbiological properties of Histosols..........;............. 7
K. R. Reddy

Chapter 3
The effect of flooding on Histosol fertility management ........ 23
G. H. Snyder

Chapter 4
The effect of flooding on insect populations..... ......... 27
R: H. Cherry

Chapter 5
The effect of flooding on nematode populations .......... 35
J. M. Good

Chapter 6
The effect of flooding on plant pathogen populations ........... 41
J. O. Strandberg

Chapter 7
The effect of flooding on weed populations .................. 57
J. A. Dusky



















EDITOR


G. H. Snyder, Ph.D.
Professor
University of Florida (IFAS)
Everglades Research and Education Center
P.O. Drawer A
Belle Glade, FL 33430


CONTRIBUTORS


Ronald H. Cherry, Ph.D.
Associate Professor
University of Florida (IFAS)
Everglades Research and
Education Center
P.O. Drawer A
Belle Glade, FL 33430

J. M. Good, Ph.D.
Former Professor and
Center Director
University of Florida (IFAS)
Everglades Research and
Education Center
P.O. Drawer A
Belle Glade, FL 33430


J. A. Dusky, Ph.D.
Associate Professor
University of Florida (IFAS)
Everglades Research and
Education Center
P.O. Drawer A
Belle Glade, FL 33430

K. R. Reddy, Ph.D.
Professor
University of Florida (IFAS)
Agricultural Research and
Education Center
P.O. Box 909
Sanford, FL 32771


J. O. Strandberg, Ph.D.
Professor
University of Florida (IFAS)
Agricultural Research and Education Center
P.O. Box 909
Sanford, FL 32771