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 Table of Contents
 Availability of Roundup ready corn...
 Nutrients in starter fertilizer...
 Starter fertilizer placement on...
 Peanut yield and tillage conservation...
 Weed control following a frost
 Weed control in white clover
 Worker standards amendment released...


FLAG IFAS PALMM UF



Agronomy notes
ALL VOLUMES CITATION SEARCH THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00066352/00065
 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: February 2006
 Subjects
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 )
 Notes
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.
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: aleph - 000956365
notis - AER9014
System ID: UF00066352:00065

Table of Contents
    Table of Contents
        Page 1
    Availability of Roundup ready corn varieties
        Page 2
    Nutrients in starter fertilizer mixtures
        Page 2
    Starter fertilizer placement on corn
        Page 2
    Peanut yield and tillage conservation systems
        Page 2
    Weed control following a frost
        Page 3
    Weed control in white clover
        Page 3
    Worker standards amendment released in new publications
        Page 4
Full Text













Vol. 30:2


AGRONOMY

UNIVERSITY OF
FLORIDA NOTES
IFAS EXTENSION


February 2006


Availability of Roundup Ready Corn Varieties
Nutrients in Starter Fertilizer Mixtures ......
Starter Fertilizer Placement on Corn ........


. . . . . . . 2
. . . . . . . 2
. . . . . . . 2


PEANUTS


Peanut Yields and Conservation Tillage Systems ........................ 2

WEED CONTROL

Weed Control Following a Frost ................. .................. 3
Weed Control in White Clover ................. .................. 3

MISCELLANEOUS

Worker Protection Standard Amendments
Released in New Publication ................. .................. 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, Interim
Dean.


IN THIS ISSUE

CORN










Availability of Roundup Ready Corn
Varieties

Performance of corn varieties can be found on
the UGA website at www.griffin.uga.edu/swvt.
There are not a lot of Roundup Ready corn
hybrids for the Deep South and therefore seed
orders should be placed early to ensure that you
have the hybrids that you want to use. Variety
information from several locations will help
growers determine what hybrids to grow and
how they perform under different environmental
conditions.

D.L. Wright

Nutrients in Starter Fertilizer Mixtures

Research has shown that sulfur from ammonium
sulfate or other compounds that leave the soil
band slightly acidic will increase phosphorus (P)
uptake in corn when applied with banded or
dribbled starter fertilizer. Ammonium
polyphosphate (10-34-0) mixed with nitrogen
solution and sulfur (28-0-0-5 or similar
materials) can increase P uptake over phosphate
materials alone. Early growth is enhanced and
corn matures earlier with starter fertilizers.

D.L. Wright

Starter Fertilizer Placement on Corn

Starter fertilizer placement is critical to good
germination and early plant growth, but fertilizer
applied in furrow can negatively impact
germination. Our research indicates that even
small amounts of in-furrow fertilizer can damage
plant stands in some cases. However, these
damaging effects are not always observed at all
locations. Regardless, it is far safer to apply
starter fertilizer in bands. If surface applied,
starter fertilizer is best as a 2"X2" placement or
2" from the row for each 201bs/A of N applied.

D.L. Wright


Peanut Yields and Conservation Tillage
Systems

Yields of crops planted in conservation tillage
systems are often different from conventional
plantings. Many years of research has shown
that yields under conservation tillage can be
much higher, much lower or about in the same
as conventional tillage. The reasons for these
yield differences vary, but in general, the large
amounts of plant residue left on the soil surface
enhance the potential for pathogen survival and
disease problems in the crop.

In conventional tillage systems, the plant residue
is incorporated into the soil. This exposes the
residue and over wintering pathogens to a very
diverse soil microbial community. The
increased contact of the plant residue with the
soil microbes increases the rate of residue
decomposition, which releases the pathogen into
a soil and decreases their survival.

Yield variability can often be explained by 1)
cover crops 2) the time the cover crops were
killed, 3) the fungi associated with
decomposition of the cover crops, or 4) previous
crop residue. Many of the main diseases of
cotton and peanut, (Pythium, Rhizoctonia,
Phytophthora, and Fusarium) need
carbohydrates and proteins for infections to
begin. Both energy and protein can be obtained
from newly killed cover crops or plant residue.
Green or newly decomposing plant material is
an ideal environment for pathogens and can set
up perfect conditions for seedling diseases.

Seedling diseases often lower crop yields when
cover crops are not killed out soon enough since
nutrients are available for pathogen growth.
Legumes decompose relatively quickly while
grass cover crops may take several weeks
longer. Cover crops decompose more quickly
when incorporated and temperatures are higher.
Therefore, in cooler years like the spring of
2005, decomposition of surface residue is much
slower. This left more food resources for plant
pathogens to infect developing crops.










Availability of Roundup Ready Corn
Varieties

Performance of corn varieties can be found on
the UGA website at www.griffin.uga.edu/swvt.
There are not a lot of Roundup Ready corn
hybrids for the Deep South and therefore seed
orders should be placed early to ensure that you
have the hybrids that you want to use. Variety
information from several locations will help
growers determine what hybrids to grow and
how they perform under different environmental
conditions.

D.L. Wright

Nutrients in Starter Fertilizer Mixtures

Research has shown that sulfur from ammonium
sulfate or other compounds that leave the soil
band slightly acidic will increase phosphorus (P)
uptake in corn when applied with banded or
dribbled starter fertilizer. Ammonium
polyphosphate (10-34-0) mixed with nitrogen
solution and sulfur (28-0-0-5 or similar
materials) can increase P uptake over phosphate
materials alone. Early growth is enhanced and
corn matures earlier with starter fertilizers.

D.L. Wright

Starter Fertilizer Placement on Corn

Starter fertilizer placement is critical to good
germination and early plant growth, but fertilizer
applied in furrow can negatively impact
germination. Our research indicates that even
small amounts of in-furrow fertilizer can damage
plant stands in some cases. However, these
damaging effects are not always observed at all
locations. Regardless, it is far safer to apply
starter fertilizer in bands. If surface applied,
starter fertilizer is best as a 2"X2" placement or
2" from the row for each 201bs/A of N applied.

D.L. Wright


Peanut Yields and Conservation Tillage
Systems

Yields of crops planted in conservation tillage
systems are often different from conventional
plantings. Many years of research has shown
that yields under conservation tillage can be
much higher, much lower or about in the same
as conventional tillage. The reasons for these
yield differences vary, but in general, the large
amounts of plant residue left on the soil surface
enhance the potential for pathogen survival and
disease problems in the crop.

In conventional tillage systems, the plant residue
is incorporated into the soil. This exposes the
residue and over wintering pathogens to a very
diverse soil microbial community. The
increased contact of the plant residue with the
soil microbes increases the rate of residue
decomposition, which releases the pathogen into
a soil and decreases their survival.

Yield variability can often be explained by 1)
cover crops 2) the time the cover crops were
killed, 3) the fungi associated with
decomposition of the cover crops, or 4) previous
crop residue. Many of the main diseases of
cotton and peanut, (Pythium, Rhizoctonia,
Phytophthora, and Fusarium) need
carbohydrates and proteins for infections to
begin. Both energy and protein can be obtained
from newly killed cover crops or plant residue.
Green or newly decomposing plant material is
an ideal environment for pathogens and can set
up perfect conditions for seedling diseases.

Seedling diseases often lower crop yields when
cover crops are not killed out soon enough since
nutrients are available for pathogen growth.
Legumes decompose relatively quickly while
grass cover crops may take several weeks
longer. Cover crops decompose more quickly
when incorporated and temperatures are higher.
Therefore, in cooler years like the spring of
2005, decomposition of surface residue is much
slower. This left more food resources for plant
pathogens to infect developing crops.










Availability of Roundup Ready Corn
Varieties

Performance of corn varieties can be found on
the UGA website at www.griffin.uga.edu/swvt.
There are not a lot of Roundup Ready corn
hybrids for the Deep South and therefore seed
orders should be placed early to ensure that you
have the hybrids that you want to use. Variety
information from several locations will help
growers determine what hybrids to grow and
how they perform under different environmental
conditions.

D.L. Wright

Nutrients in Starter Fertilizer Mixtures

Research has shown that sulfur from ammonium
sulfate or other compounds that leave the soil
band slightly acidic will increase phosphorus (P)
uptake in corn when applied with banded or
dribbled starter fertilizer. Ammonium
polyphosphate (10-34-0) mixed with nitrogen
solution and sulfur (28-0-0-5 or similar
materials) can increase P uptake over phosphate
materials alone. Early growth is enhanced and
corn matures earlier with starter fertilizers.

D.L. Wright

Starter Fertilizer Placement on Corn

Starter fertilizer placement is critical to good
germination and early plant growth, but fertilizer
applied in furrow can negatively impact
germination. Our research indicates that even
small amounts of in-furrow fertilizer can damage
plant stands in some cases. However, these
damaging effects are not always observed at all
locations. Regardless, it is far safer to apply
starter fertilizer in bands. If surface applied,
starter fertilizer is best as a 2"X2" placement or
2" from the row for each 201bs/A of N applied.

D.L. Wright


Peanut Yields and Conservation Tillage
Systems

Yields of crops planted in conservation tillage
systems are often different from conventional
plantings. Many years of research has shown
that yields under conservation tillage can be
much higher, much lower or about in the same
as conventional tillage. The reasons for these
yield differences vary, but in general, the large
amounts of plant residue left on the soil surface
enhance the potential for pathogen survival and
disease problems in the crop.

In conventional tillage systems, the plant residue
is incorporated into the soil. This exposes the
residue and over wintering pathogens to a very
diverse soil microbial community. The
increased contact of the plant residue with the
soil microbes increases the rate of residue
decomposition, which releases the pathogen into
a soil and decreases their survival.

Yield variability can often be explained by 1)
cover crops 2) the time the cover crops were
killed, 3) the fungi associated with
decomposition of the cover crops, or 4) previous
crop residue. Many of the main diseases of
cotton and peanut, (Pythium, Rhizoctonia,
Phytophthora, and Fusarium) need
carbohydrates and proteins for infections to
begin. Both energy and protein can be obtained
from newly killed cover crops or plant residue.
Green or newly decomposing plant material is
an ideal environment for pathogens and can set
up perfect conditions for seedling diseases.

Seedling diseases often lower crop yields when
cover crops are not killed out soon enough since
nutrients are available for pathogen growth.
Legumes decompose relatively quickly while
grass cover crops may take several weeks
longer. Cover crops decompose more quickly
when incorporated and temperatures are higher.
Therefore, in cooler years like the spring of
2005, decomposition of surface residue is much
slower. This left more food resources for plant
pathogens to infect developing crops.










Availability of Roundup Ready Corn
Varieties

Performance of corn varieties can be found on
the UGA website at www.griffin.uga.edu/swvt.
There are not a lot of Roundup Ready corn
hybrids for the Deep South and therefore seed
orders should be placed early to ensure that you
have the hybrids that you want to use. Variety
information from several locations will help
growers determine what hybrids to grow and
how they perform under different environmental
conditions.

D.L. Wright

Nutrients in Starter Fertilizer Mixtures

Research has shown that sulfur from ammonium
sulfate or other compounds that leave the soil
band slightly acidic will increase phosphorus (P)
uptake in corn when applied with banded or
dribbled starter fertilizer. Ammonium
polyphosphate (10-34-0) mixed with nitrogen
solution and sulfur (28-0-0-5 or similar
materials) can increase P uptake over phosphate
materials alone. Early growth is enhanced and
corn matures earlier with starter fertilizers.

D.L. Wright

Starter Fertilizer Placement on Corn

Starter fertilizer placement is critical to good
germination and early plant growth, but fertilizer
applied in furrow can negatively impact
germination. Our research indicates that even
small amounts of in-furrow fertilizer can damage
plant stands in some cases. However, these
damaging effects are not always observed at all
locations. Regardless, it is far safer to apply
starter fertilizer in bands. If surface applied,
starter fertilizer is best as a 2"X2" placement or
2" from the row for each 201bs/A of N applied.

D.L. Wright


Peanut Yields and Conservation Tillage
Systems

Yields of crops planted in conservation tillage
systems are often different from conventional
plantings. Many years of research has shown
that yields under conservation tillage can be
much higher, much lower or about in the same
as conventional tillage. The reasons for these
yield differences vary, but in general, the large
amounts of plant residue left on the soil surface
enhance the potential for pathogen survival and
disease problems in the crop.

In conventional tillage systems, the plant residue
is incorporated into the soil. This exposes the
residue and over wintering pathogens to a very
diverse soil microbial community. The
increased contact of the plant residue with the
soil microbes increases the rate of residue
decomposition, which releases the pathogen into
a soil and decreases their survival.

Yield variability can often be explained by 1)
cover crops 2) the time the cover crops were
killed, 3) the fungi associated with
decomposition of the cover crops, or 4) previous
crop residue. Many of the main diseases of
cotton and peanut, (Pythium, Rhizoctonia,
Phytophthora, and Fusarium) need
carbohydrates and proteins for infections to
begin. Both energy and protein can be obtained
from newly killed cover crops or plant residue.
Green or newly decomposing plant material is
an ideal environment for pathogens and can set
up perfect conditions for seedling diseases.

Seedling diseases often lower crop yields when
cover crops are not killed out soon enough since
nutrients are available for pathogen growth.
Legumes decompose relatively quickly while
grass cover crops may take several weeks
longer. Cover crops decompose more quickly
when incorporated and temperatures are higher.
Therefore, in cooler years like the spring of
2005, decomposition of surface residue is much
slower. This left more food resources for plant
pathogens to infect developing crops.










Many root and stem diseases can influence plant
growth all year without severe visual symptoms.
This may be one reason that peanut yields were
not as good for some people using conservation
tillage in 2005. One way to avoid this situation
is to kill out the cover crop earlier in the year so
that the carbohydrates and proteins are expended
before the pathogen get started. Preliminary
research with bahiagrass also shows that peanut
yields can be 1000-1500 lbs/A higher if
bahiagrass is killed in the fall as compared to the
spring prior to planting peanuts. Additional
research is underway to determine how to make
yield consistently higher with conservation
tillage.

D.L. Wright and J.J. Marois

Weed Control Following a Frost

Frost is common during the winter months in
north Florida, but it tends to be a little less
frequent and not as damaging to plants in south
Florida. This year has been an exception.
During January, at least one heavy frost
occurred at the Range Cattle REC in January. A
lot of annual plants did not survive the frost
event, and leaf tissue on many perennial plants
was damaged, while others (mainly biennials)
were unaffected.

The effect of frost on a plant can be detrimental
to weed control. In general, herbicides work
poorly on plants that have recently been
damaged by frost. This is especially true for
systemic herbicides such as glyphosate, 2,4-D,
aminopyralid, triclopyr, and others. It is best to
wait a few days until new growth appears before
applying the herbicide.

Plants that are unaffected by cold temperatures
and frost can be treated at almost any time, but
temperature at and after herbicide application is
most important. For example, musk thistle, a
biennial species present in north Florida, control
was greater than 90% when 2,4-D was applied
when air temperature was above 50 F.
However, if air temperature was less than 500 F,


musk thistle control can drop as low as 50%.

In summary, it is best to scout the field/pasture
before herbicide application after a frost event.
If plants show damage, it is best to wait a few
days for new growth to appear before applying
herbicides. For species not damaged by frost,
delaying herbicide application until air
temperatures are above 500 F can dramatically
improve weed control.

B.A. Sellers

Weed Control in White Clover

Clover can provide great benefits in a winter
grazing system. Research has shown that cattle
grazed on clover/grass mixtures perform better
than those on grass alone. However, managing
weeds in mixed stands of clover can be very
difficult, if not impossible.

In white clover, 1 pt of 2,4-D amine can be
applied during the winter. This application will
cause stunting and reduce clover stand density,
but the clover will tolerate to this application
quite well. The drawback to this application is
that 1 pt of 2,4-D amine applied in the winter
will generally not control all the weeds present.
Acceptable control of evening primrose will be
observed, but many species (such as red sorrel
and henbit) will not be controlled.

Considering the sensitivity of clover to most
available pasture herbicides, controlling weeds
while preserving the grazing stand is almost
impossible. This situation leaves basically two
options: 1) do nothing about the weeds, or 2) kill
the weeds and the clover. If weed density is not
excessive, the best option is to do nothing.
Animals will selectively graze some weeds and
since there are no highly effective herbicides,
non-treatment can be a good decision. However,
if weed populations are sufficiently high to
decrease grazing and impede green-up of the
summer forage, then weed control becomes
much more important. In this situation,










Many root and stem diseases can influence plant
growth all year without severe visual symptoms.
This may be one reason that peanut yields were
not as good for some people using conservation
tillage in 2005. One way to avoid this situation
is to kill out the cover crop earlier in the year so
that the carbohydrates and proteins are expended
before the pathogen get started. Preliminary
research with bahiagrass also shows that peanut
yields can be 1000-1500 lbs/A higher if
bahiagrass is killed in the fall as compared to the
spring prior to planting peanuts. Additional
research is underway to determine how to make
yield consistently higher with conservation
tillage.

D.L. Wright and J.J. Marois

Weed Control Following a Frost

Frost is common during the winter months in
north Florida, but it tends to be a little less
frequent and not as damaging to plants in south
Florida. This year has been an exception.
During January, at least one heavy frost
occurred at the Range Cattle REC in January. A
lot of annual plants did not survive the frost
event, and leaf tissue on many perennial plants
was damaged, while others (mainly biennials)
were unaffected.

The effect of frost on a plant can be detrimental
to weed control. In general, herbicides work
poorly on plants that have recently been
damaged by frost. This is especially true for
systemic herbicides such as glyphosate, 2,4-D,
aminopyralid, triclopyr, and others. It is best to
wait a few days until new growth appears before
applying the herbicide.

Plants that are unaffected by cold temperatures
and frost can be treated at almost any time, but
temperature at and after herbicide application is
most important. For example, musk thistle, a
biennial species present in north Florida, control
was greater than 90% when 2,4-D was applied
when air temperature was above 50 F.
However, if air temperature was less than 500 F,


musk thistle control can drop as low as 50%.

In summary, it is best to scout the field/pasture
before herbicide application after a frost event.
If plants show damage, it is best to wait a few
days for new growth to appear before applying
herbicides. For species not damaged by frost,
delaying herbicide application until air
temperatures are above 500 F can dramatically
improve weed control.

B.A. Sellers

Weed Control in White Clover

Clover can provide great benefits in a winter
grazing system. Research has shown that cattle
grazed on clover/grass mixtures perform better
than those on grass alone. However, managing
weeds in mixed stands of clover can be very
difficult, if not impossible.

In white clover, 1 pt of 2,4-D amine can be
applied during the winter. This application will
cause stunting and reduce clover stand density,
but the clover will tolerate to this application
quite well. The drawback to this application is
that 1 pt of 2,4-D amine applied in the winter
will generally not control all the weeds present.
Acceptable control of evening primrose will be
observed, but many species (such as red sorrel
and henbit) will not be controlled.

Considering the sensitivity of clover to most
available pasture herbicides, controlling weeds
while preserving the grazing stand is almost
impossible. This situation leaves basically two
options: 1) do nothing about the weeds, or 2) kill
the weeds and the clover. If weed density is not
excessive, the best option is to do nothing.
Animals will selectively graze some weeds and
since there are no highly effective herbicides,
non-treatment can be a good decision. However,
if weed populations are sufficiently high to
decrease grazing and impede green-up of the
summer forage, then weed control becomes
much more important. In this situation,










maintaining the clover stand is not likely
possible and reseeding should be planned.

Clover grows best when winter rainfall is
plentiful and a dry winter will lead to less
available clover. If the winter has been dry and
little clover is present anyway, this may be the
best time to consider controlling all your weeds
and starting over. The bahiagrass will green-up
faster this spring and there should be fewer
weeds next winter to interfere with clover
growth.

J.A. Ferrell

Worker Protection Standard Amendments
Released in New Publication

The Worker Protection Standard (WPS) became
Federal regulation in 1992 and fully
implemented in 1995. Its purpose is to reduce
the risk of pesticide-related illness and injury of
agricultural workers and pesticide handlers who
are employed by farm, nursery, forest, and
greenhouse operations. The WPS regulations
were explained in the original How to Comply
manual; however, since that time, several
amendments were made to the WPS.


The UF/IFAS EDIS Document, A Summary of
Revisions to the Worker Protection Standard,
was originally published in 1998 and since
modified to include these amendments. The
document provides a quick review of 6 main
areas that have been modified by the EPA: 1)
grace period for providing worker safety
training, 2) exemption of crop advisors from
certain provisions of the WPS, 3) exceptions to
WPS early entry prohibition for irrigation and
limited contact activities, 4) reduced restricted
entry intervals for some pesticides, 5) reduced
time for decontamination supplies, and 6)
changes in size and language for field posting
signs. The document may be viewed at:
http://edis.ifas.ufl.edu/PI017.

This past fall, the EPA finalized its revision of
the How to Comply manual and released the
publication. The full 141-page document may be
viewed at http://www.epa.gov/agriculture/epa-
735-b-05-002.pdf Although a limited number of
paper copies of the manual are on hand, the
UF/IFAS Pesticide Information Office will
provide them on a first-come-first-serve basis.
Call Willene Johnson at (352) 392-4721 or
email at willene@ufl.edu if you are interested.

F.M. Fishel


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
products.
Prepared by: J.M. Bennett, Chairman; M.B. Adjei, Forage Agronomist (mbadjei@ifas.ufl.edu); J.A. Ferrell, Extension Agronomist
(jaferrell@ifas.ufl.edu); F.M. Fishel, Pesticide Coordinator (weeddr@ifas.ufl.edu); C.R. Rainbolt, Extension Agronomist
(crrainbolt@ifas.ufl.edu); B.A. Sellers, Extension Agronomist (sellersb@ifas.ufl.edu); E.B. Whitty, Extension Agronomist
(ebw@ifas.ufl.edu); D.L. Wright, Extension Agronomist (dlw@ifas.ufl.edu).