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Agronomy notes
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066352/00093
 Material Information
Title: Agronomy notes
Uniform Title: Agronomy notes (Gainesville, Fl.)
Physical Description: v. : ill. ; 28 cm.
Language: English
Creator: Florida Cooperative Extension Service
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.
Place of Publication: Gainesville
Creation Date: October 2007
Subjects / Keywords: Crops and soils -- Florida   ( lcsh )
Crop yields -- Florida   ( lcsh )
Agriculture -- Florida   ( lcsh )
Agronomy -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
periodical   ( marcgt )
serial   ( sobekcm )
Statement of Responsibility: Florida Cooperative Extension Service, University of Florida, Institute of Food and Agricultural Sciences.
General Note: Description based on: January 1971; title from caption.
 Record Information
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000956365
notis - AER9014
System ID: UF00066352:00093


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Vol. 31:10 October 2007

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D deciding on D efoliating Cotton.................................. ............................ 2

Use of Winter Annuals for Overseeding on Grass Sods..................................
Small Nitrogen Fertilizer for Seedlings of Overseeded Legumes ........................3
Fall Soil Sam pling for Forage Production ........................................ ...................3

Spread of A sian Soybean Rust.................................... ............................ 3

Is V volunteer C orn a W eedy C concern? ........................................ .......................3
Operation Cleansweep for Pesticides.............. ....................................................4

Problem areas in crop fields...................................................... ............... 4
Crops for B iodiesel ........................................... ........................ ........ .4

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Employment Opportunity _Affirmative Action Employer authorized to
provide research, educational information and other services only to individuals and institutions that function without regard to race, color,
sex, age, handicap or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension
Office. Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Larry Arrington, Dean.

Deciding on Defoliating Cotton

Cotton requires about 55-60 days from bloom to
open boll depending on heat units. July and
August temperatures were above normal this
year resulting in faster maturity. Cotton usually
requires from 135-155 days from planting
harvesting in Florida. Many unirrigated fields
had very slow emergence this year due to dry
seedbeds with cotton emerging over a 6-8 week
period. When this happens, it extends the period
that cotton has to be protected from pests
resulting in a more expensive crop. Decisions
about defoliation and boll opening can affect
quality and storage time if the crop is put into
modules. Stain from poorly defoliated plants or
regrowth and moisture from the green tissue
cause the biggest loss in quality. Most growers
use the criteria of 60% open bolls as the time
that defoliants should be put out on cotton to
open the remainder of the bolls and knock off
leaves in preparation for harvest. Another
method to determine defoliation timing is nodes
above cracked bolls (NACB). Research has
shown that cotton with four nodes above the
highest cracked boll can be defoliated without
significant weight or quality loss. IfNACB
counts average five or more, defoliant
applications should be delayed. Bolls set in
mid-summer are usually larger and mature in 40
to 50 days, while the bolls set in August can take
60 days or longer to mature and often contribute
little to final yield if the crop had a normal
fruiting season. If there is a good crop set on the
plant, do not wait on late flowering bolls since
the loss to the larger bolls set earlier will be
more than is gained by late fruit set. It has been
shown, many times, that the fruit set during the
first 3-4 weeks of bloom normally contributes 90
to 95% of the total yield of the cotton crop.
Cotton should be harvested about 2 weeks after
defoliation. For more information on materials
to use in defoliating cotton go to
http://edis.ifas.ufl.edu/AG188 .

David Wright

Use of Winter Annuals for Overseeding on
Grass Sods

Winter annuals like annual ryegrass, small
grains, and legumes can be used used in North-,

Central-, and parts of South Florida to extend the
grazing season and increase the quality of the
diet for the grazing livestock when bahiagrass
and bermudagrass are dormant and
unproductive. These annuals will add to the
nutritive value of your animal's diet, thus,
reducing the amount of expensive energy and
protein winter supplement as well as the need
for stored forages. Spring weed control and
addition of nitrogen (ifoverseeding clovers or
legumes) are additional benefits of winter annual
overseeding. Fall is a time when the tail end of
production of bahia- and bermudagrass overlap
with the initial growth of winter annuals.
Certain management practices need to be used to
guarantee the successful establishment of cool-
season annuals overseeded on grass sods. Some
of these practices include: allowing your
bahiagrass or bermudagrass to grow for 4 to 5
weeks before overseeding but making sure that
the top growth is removed as hay or by flash
heavy grazing before planting the winter
annuals. The open sod created by late
harvesting and removal of top growth will be
less competitive to the up-and-coming winter
annual seedlings. Another practice to reduce
bahia- and bermudagrass competition is to do a
very light disking or passing the disc with the
blades straight-doing so will only loosen the
grass sod and allow more seed and soil contact;
light disking is critical to achieve success when
early planting. Some herbicides like Gramoxone
(paraquat) or Round-up (glyphosate) used at low
rates have been used to suppress growth on the
grass sods but they are an additional cost, do not
guarantee the early production of the winter
annuals, and may cause stand loss of the grass
sod (this last method is not a preferred or a
recommended one). Once you have removed the
top growth of the grass sod and light disked the
field, proceeded with the planting of the seed
(ideal conditions are after a 'soaking' rain). You
can overseed your winter annuals 4 to 6 weeks
before the average freeze that will bum down
the top growth of your grass sod; night
temperatures should be in the mid 60's and day
temperatures in the low 80's. After planting, do
not forget to roll the field to seal in the moisture.

Yoana Newman

Small Nitrogen Fertilizer for Seedlings of
Overseeded Legumes

Effective nodulation takes place within 4 weeks
or one month after planting. The implication is
that during those first 3 to 4 weeks the plant
relies mainly on the soil nutrients, included
nitrogen, because the nodules are not fully
functional. This is the reason why it is
recommended to fertilize small amounts of N to
help out the legume seedlings only during the
first weeks. What is considered a small N
fertilization? Anything under 20 to 25 lb N/acre.
All other nutrients should be applied according
to soil test recommendations. Because legumes
fix nitrogen we do not want to apply nitrogen to
established legumes because the nodules shut
down and become ineffective at fixing nitrogen.
It is only during establishment that small
additions of Nitrogen fertilizer will increase
nodulation. In general, do not apply N fertilizer
to legume stands, except low amounts during
establishment, and follow with the
recommended fertilization of other elements,
specially Phosphorus and micronutrients

Yoana Newman

Fall Soil Sampling for Forage Production

Soil samples collected in late October and
November can be analyzed and results returned
in time to plan for February and March
applications of lime and fertilizer. In October
and November, pastures are usually dry enough
so that samples can be collected without
interference from excessive moisture.

Yoana Newman

Spread of Asian Soybean Rust

During the last few weeks of September Asian
soybean rust has been identified in the major
soybean producing counties in Florida with most
of the sentinel plots or monitored kudzu sites
coming up positive. The extreme temperatures
and dry weather in July and August made the
disease to progress slowly until temperatures
cooled off in September. There are several late
planted fields of soybeans that were planted after
irrigated corn that will have to be monitored
closely to make sure that the disease is

controlled through R6 stage of growth. This is
when the green bean has completely filled the
pod. Rust has been found in only a few
commercial fields and has not spread rapidly to
this point. Some fields have been sprayed by
producers at early bloom and pod fill; these
fields will have to be watched for onset of the
disease up until about R6. With soybean prices
at highs of the past two decades, growers are
sure to plant more soybeans next year. If you
are not sure if you have soybean rust in your
fields or even in your county, check with your
county agent to see where it has been found.
Models are being developed to help growers
determine if conditions are conducive for spread
of the rust. For more in-depth information on
Asian soybean rust go to the website at

David Wright and Jim Marois

Is Volunteer Corn a Weedy Concern?

The recent interest in biofuels has dramatically
increased commodity prices; corn in particular.
Currently, corn is trading at over $3.50/bu with
futures over $4/bu. At this price many growers
are considering planting corn after corn for
several cycles. However, volunteer corn is
likely to become a weed using this strategy.

Volunteer corn can be a problem because these
non-hybrid, inbred lines often have extremely
low productivity. But, this does keep the plant
from aggressively using water, nutrients and
light that is needed by the adjacent crop.
Additionally, removing a weedy corn from a
corn crop is extremely difficult with herbicides
and often required an expensive tillage
operation. So the question arises, how much
volunteer corn is necessary before it becomes
economically feasible to perform a control

Extensive surveys have been conducted across
the mid-west for the last two years to determine
common volunteer infestation levels and their
yield impact. It was found that the majority of
fields had volunteer corn infestation too low to
cause yield impact (1,000 to 4,000 plants per
acre) while only 12% had yield threatening
levels. So, by and large volunteer corn can be
ignored since yield reduction will likely not take

place. However, if populations are high, there
are only 2 options: in-season cultivation, and
planting a resistant corn variety.

When planning a resistant variety, selection can
be difficult. If the previous crop was Roundup
Ready, the volunteer corn will contain the
resistance gene. In this case, a Liberty-Link
variety is the only solution. However, if the
previous variety was Roundup Ready with
Herculex (for insect protection), the volunteer
will contain both Roundup and Liberty
resistance. Regardless, these options should not
be considered unless the volunteers reach a
population exceeding 10,000 plants per acre.

Jason Ferrell

Operation Cleansweep for Pesticides

Operation Cleansweep is a mobile collection
program that provides agricultural producers a
safe and economical method of disposing of
cancelled, suspended and unusable pesticides.
Proper disposal can be expensive and place a
regulatory burden on small agricultural
producers and dealers. Operation Cleansweep
offers an opportunity to avoid these barriers and
to promote safe and environmentally sound
pesticide use, handling and disposal. Operation
Cleansweep was initiated in 1995 with the major
objective of collecting lead arsenate, a widely
used pesticide in Florida citrus production, but
banned for use by the EPA in 1978. During
1995, Operation Cleansweep collected more
than 70,000 pounds of lead arsenate. Statewide
surveys have identified substantial quantities of
cancelled, suspended and unusable pesticides
stored throughout Florida. Some of these
materials have been in confinement for many
years and are in containers unsuitable for proper
storage. Some, such as chlordane and DDT, are
no longer allowed to be used.

Operation Cleansweep provides for a contractor
to come directly to a farm or pesticide
application business for pickup and disposal of
pesticides when there is a sufficient quantity in a
defined area. There is no cost charged to those
who participate in the program. For more
information, call the Florida Department of
Agriculture and Consumer Services by calling
toll-free 877-851-5285 or email

Cleansweep(@doacs.state.fl.us. This year's
deadline for being added to the pickup list is
December 15.

Cleansweep Website:

IFAS facilities should contact UF Environmental
Health and Safety to schedule a pickup date for
old materials. Go online at
as or call 352-392-8400 to submit a chemical
pickup request.

Fred Fishel

Problem areas in crop fields

As harvest season progresses make a note of the
areas of the fields that appear to have lower
yields or plants that look unhealthy. Many of
these problem areas can be minimized with
future crops if you know the cause. Soil
samples for nematodes as well as nutrient
analysis can help determine the cause of the
problem and then certain management practices
or rotations can be followed to minimize the
impact. Good soil sampling is key to
understanding problems. Always get samples
from different soil types in the field as well as
those areas that yielded differently and compare
them. In many cases soil type, which
determines water and nutrient holding capacity,
may make the most difference in yield
variability. However, some crops do better on
sandy soils than others and crops can be chosen
for those fields that do well. Keep a record of
what is happening in each field as far as fertility
and nematode levels.

David Wright

Crops for Biodiesel

The climate and soils of Florida are conducive to
grow many crops. Biofuels are a hot topic in all
of the farm magazines as well as with consumers
who are having to pay more for energy than
ever. The table below shows crops that can be
used for biodiesel and the approximate amount
of biodiesel that can be expected from average
yields of those crops.

Farmers in Florida have had many acres of corn,
oats, cotton, soybean, sunflower, peanut, and
Canola. The other crops can be grown if it is
economical and if there is an infrastructure for

handling them. Yields of the crops shown below
are average yields but with good management
about 25-40% better yields can be obtained.

David Wright

Oil Producing Crops
Plant Yield (seed) Biodiesel Plant Yield (seed) Biodiesel
lbs/acre gal/acre lbs/acre gal/acre
Corn 7800 18 Safflower 1500 83
Oats 3600 23 Rice 6600 88
Cotton 1000 35 Sunflower 1200 100
Soybean 2000 48 Peanut 2800 113
Mustard 1400 61 Canola/Rape 2000 127
Camelina 1500 62 Coconut** 3600 287
Crambe 1000 65 Oil palm** 6251 635
** Yield given in lbs of oil/acre
Source: Biofuel Variety Trails Factsheet, USDA-ARS and WSU, Prosser, WA

The use of trade names does not constitute a guarantee or warrant of products named and does not signify approval to the exclusion of similar
Prepared by: J.M. Bennett, Chairman; J.A. Ferrell, Extension Agronomist .Ii.ill, .i i.li .. F.M. Fishel, Pesticide Coordinator
(' ... I 11 i ..i, Jim Marois, Plant Pai..i..-; i ""...; ,, .i ,..i YoanaNewman, Extension Forage Specialist -.., ,,i .1..i D.L.
Wright, Extension Agronomist (dlw@ifas.ufl.edu).