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Agronomy notes
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Permanent Link: http://ufdc.ufl.edu/UF00066352/00094
 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: November 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: UF00066352:00094


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Vol. 31:11 November 2007

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Cotton Defoliation ...................... ................. ............ ....2


M anure Applications vs. Fertilizer and Soil pH ......................................................2
Overseeding Cool-season Annuals into Bahiagrass or Bermudagrass ...............2
Perennial Peanut Window for Planting in Florida and Fall Measures .................3


Pastures: The High Price of M owing.................................................................. 3
W eed C control Inventory ............................................ .............................. 4


Fertilizer Prices and Usage in Corn and Rotation with Soybean.............................4
R stations M matter ..................................... ...................... ...... ..... .....
Tillage and Soil Organic M atter ..................... ............................................. 5

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.

Cotton Defoliation

Cotton can be defoliated without yield loss
when at least 60% of the cotton is open.
Defoliants and boll openers work together to
remove leaves and open all mature bolls
within a two week period after treatment.
Picking ahead of this schedule may result in
unopened bolls and leaves, or more trash in
the seed cotton and, consequently, more
discounts. Generally, defoliants and boll
openers work better under warmer
conditions and with lower rates than later in
the season when temperatures are cooler.
Some of the early picked cotton has had low
micronaire in the discount range this year. It
is normally expected that cotton that
develops under hot conditions will have high
mike. The lower mike may be due to the
extreme drought and heat that resulted in
cotton bolls being set later in the season, and
is more of a result of immature fibers and
less cell wall thickening. Try to time
defoliation about 2 weeks before picking
since the wet fall is causing regrowth. If not
picked within that time frame, it would have
to be defoliated again.

David Wright

Manure Applications vs. Fertilizer and
Soil pH

Generally manure applications from cattle
grazing fields will result in somewhat
constant soil pH levels. Most of the
reduction in soil pH is due to nitrogen
applications. Fallow fields and fields that
have no fertilizer applications show very
slow reductions in pH. Therefore, if cattle
are stocked on perennial grasses and winter
annuals, and these fields are used in rotation
with row crops, pH may be maintained at a
higher level than if cattle were not part of
the system. Also, much research shows that
cattle manure enriches some microbial
communities that favor higher soil
productivity through maintenance of higher

pH and stimulates activity of several
enzymes involved in N and P

David Wright

Overseeding Cool-season Annuals into
Bahiagrass or Bermudagrass

Use of cool-season forage legumes was
popular before chemical fertilizers became a
cheap resource not only because of their
natural nitrogen fixation ability but also
because of their high nutritive value with
protein concentration of 20% or more on a
dry basis. It is remarkable to see the early
literature showcasing success stories in
Florida with the use of cool season legumes
like crimson clover, red clover, whiteclover,
and many others like berseem, sweetclover,
and lupine, whose seed production gave in
to the cheap fertilizer. With the hike in
fertilizer prices, forage legumes interest is
back. Next, are a couple of pointer items if
you are overseeding cool-season annuals
and particularly legumes:

Overseeding into warm-season perennial
grasses requires that you open the sod to
help germination of the legume or ryegrass
seed. To achieve that objective, lightly disk
the area 1 to 2 inches deep, then broadcast
the seed. If using a drill, make sure that the
seed is placed at the right depth: clover and
ryegrass no deeper than 14 inch; small grains
1 inch deep. After broadcasting the seed roll
or pack the area to seal in moisture and
increase the seed to soil contact. If
overseeding clovers, make sure to use a
variety that is best suited to your soils and to
use the right inoculums with the proper
nitrogen fixing bacteria for your seed.

Yoana Newman

Perennial Peanut Window for Planting
in Florida and Fall Measures

If planning on planting perennial (rhizoma)
peanut, fall should not be targeted for
planting but instead for doing the weed
control and getting the field ready to sprig
later in winter and early spring. At this time
in fall and through January or February,
weed control is the goal and can be
accomplished by harrowing. Care must be
taken not to apply any chemical for weed
control as it would affect the emergence of
the perennial peanut later in the spring. You
should wait and dig the rhizomes (or
underground stems) while they are dormant.
Fall is not recommended for digging
because, at this time, perennial peanut is
placing all the energy reserves into the
underground rhizomes, and you want to dig
them when they are fully 'charged' as this is
the energy they will use mainly for coming
up. A practical rule of thumb is to dig and
plant the peanut when it is dormant, or
before it breaks dormancy in the spring-the
window for planting in Florida under rain
fed conditions is any time after Christmas
through early March. Recommended
planting rate is 80 bushels/acre or more if
material is available. Fertilization should
follow in the spring only after the peanut has
initiated active root growth, usually when
nighttime temperatures are consistently
above 600F, otherwise if you put the
fertilizer too early you will be feeding the

These recommendations are for rain fed
conditions. The key to successful planting
and establishment is available water. If
irrigation is available some exceptions can
be made like extending the planting window
later in the spring. For a list of Perennial
Peanut providers, please see extension
publication from University of Florida -
IFAS titled: 2007 Perennial Peanut Source
List of Planting Material (Rhizomes) and

Hay; available on line at:
http://edis.ifas.ufl.edu/AG105 or through
your extension county agent.

Yoana Newman

Pastures: The High Price of Mowing

The use of herbicides has almost been
second-nature for crop producers for over 30
years. However, cattle ranchers have
traditionally used fewer herbicides because
increasing grass yield is rarely critical to
maximizing profit; herbicides were
expensive, and mowing was cheap.
However, we have seen a reversal of these
trends in the past 5 years. As a rule, the
price of diesel fuel has more than doubled
and labor prices have steadily increased.
Meanwhile herbicides prices have remained
steady or decreased. Believe it or not, in
many instances it is now cheaper to spray
herbicides than to mow.

A recent economic cost analysis concluded
that mowing can cost as much as $15 per
acre when fuel, machinery cost, and labor
are calculated. Also, very few weeds will be
controlled by mowing. True, timely
mowing of weeds such as dogfennel (in the
late summer) can often make these weeds
disappear for the remainder of the season.
However, dogfennel will readily resprout the
next season as if the mowing never
occurred. Conversely, a timely application
of 2,4-D, Cleanwave + 2,4-D, or 2,4-D +
dicamba can adequately control dogfennel
for as little as $11 to $15 per acre
(application cost included).

Granted, not all weeds can be controlled this
inexpensively. Brush weeds such as
blackberry, or invasive species like tropical
soda apple will require a greater investment.
But, mowing is not necessary for either of
these weeds and in the case of blackberry
can even decrease control if not timed

properly. Therefore, consider which weeds
you are currently battling and whether
herbicides can improve weed control and
your bottom line.

Jason Ferrell

Weed Control Inventory

The 2007 growing season should be slowing
down within the next few weeks. This is the
perfect time to make a weed control
inventory while all the details of this season
are still fresh in your mind. In particular,
make a list of all the weeds that were easily
managed and which weeds were not well
controlled and start planning a weed control
strategy to address the unmet needs. Those
who wait until next season to start the
planning process will generally forget
important details, reuse the same herbicide
strategies, and battle the same weeds again
in 2008. But, a proactive approach will
address these issues well in advance and
hopefully provide better weed control
solutions. For assistance in planning and
utilizing the most current weed control
information, please contact your local
county extension office.

Jason Ferrell

Fertilizer Prices and Usage in Corn and
Rotation with Soybean

Corn acreage was up dramatically this year
due to price at corn planting time. Corn has
one of the highest fertilizer requirements of
any crop and even though weather was
erratic and acreage was up, this may be a
record crop of about 154 bu/A average in the
U.S. Yields of corn have continued to
increase as better hybrids have been
developed and genetic technology has
reduced the damage done by pests and
drought. With higher yields, higher rates of
nutrients have been removed from fields
with both grain and silage. The average use
of fertilizer on a per acre basis in 1950 was

N-17 lbs/A, P-26 lbs/A as the oxide, and K-
17 lbs/A as the oxide. In 2000, the average
fertilizer use rate had risen to: N- 150 lbs/A,
P- 64 lbs/A, and K- 91 lbs/A. Soybean
prices have risen since early spring so that
more beans may be planted in the coming
year. Soybeans respond little to direct
fertilization but do respond to residual
fertility and good soils. The higher corn
acreage this year may result in better
soybean yields in another year. Genetic
technology is being developed for corn that
will allow better nitrogen utilization and
may reduce lime needs as rates are lowered.

David Wright

Rotations Matter

Rotation results in higher yields of following
crops and less pesticide use due to less pest
pressure. This is one of the oldest
management practices and one that is often
not followed well. There are many reasons
for lack of rotation implementation
including low prices for good rotation crops
and lack of equipment for planting or
harvesting the other crops. Prices for
several commodities are good now so
consider some of the crops that you may not
have grown for a number of years that will
make a good rotation. Generally, legume
crops should follow grass crops or cotton to
reduce nematodes and many of the hard to
control weeds can be controlled when
different classes of herbicides can be used
on the rotation crop. In our bahiagrass
rotation studies using cotton and peanut,
nematode levels are several folds lower
when bahiagrass is in the rotation for 2 years
and no nematicides were needed; levels
were high enough in the rotation with 2
years of cotton followed by peanuts that a
nematicide did have to be used for optimum

David Wright

Tillage and Soil Organic Matter

Tillage continues to reduce OM content of
the soil. Much of the SE is now using strip
tillage for cotton, corn, peanuts and other
row crops. However, after many years of
winter annual cover crops, little or no build
up of OM is occurring. Recent work with
bahiagrass in rotation with cotton and peanut
has shown that we can increase soil OM by
about one tenth of a percent per year. When
you consider this OM increase vs. the OM
reduction that has occurred in the Midwest,
where OM content of the soil has decreased
from about 4% when it was plowed out of
native prairie grasses to 1% in many areas
over the last 100 years as shown by long

term plots at several universities-
implications are that we would be able to
gain about 1% OM in our SE soils in a 10
year period. This fact can have a significant
impact on fertility, water holding capacity,
yield, and crop quality. The Magruder plots
in Oklahoma were plowed out of prairie
grasses in 1892 and planted to wheat every
year since then and did not respond to
nitrogen applications until 65 years later due
to the high OM soils releasing nitrogen for
the crops. We do have an economically
viable option to get back to those types of
farms using perennial grasses in our farming

David Wright

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 i .I.l, I.I i. .I ... Yoana Newman, Extension Forage
Specialist 1.- ..i ...I D.L. Wright, Extension Agronomist (dlw@ifas.ufl.edu).