AGRONOMY

UNIVERSITY OF
FLORIDA
IFAS EXTENSION

Vol. 31:2 February 2007

IN THIS ISSUE

CORN

B est C orn H ybrids in Short Supply ........................................ ........................2

Corn for Ethanol Production......................... .... ............................... 2

What Is Too Early to Plant Corn? ..... ..................... ...............2

Corn Nitrogen Use and Prices ..................... .............................................. 2

FORAGE

R yegrass K nocked O ut ........................................... ............................... 3

WEED CONTROL

Glyphosate Resistance Still Increasing.................................. ..... ............ 3

MISCELLANEOUS

Am I in Compliance with FDACS Pesticide Law? ............................................. 4

H igh N itrogen Requiring Crops and Soil Ph ...........................................................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.

Best Corn Hybrids in Short Supply

What a difference a year can make. Corn
seed supplies are limited for the best hybrids
due to the expected increase in corn acreage.
This increase is being fueled almost entirely
by ethanol plants. There are still several
hybrids with the Roundup trait that can be
used in Florida but they may require more
management due to little disease resistance.
Therefore, it is necessary to place orders
early to ensure that you are able to get the
hybrids that you desire. Plant diseases (rust
and leaf blight) are one of the main
impediments to harvesting high quality corn
silage and grain. Severe disease outbreak
often results in corn dying 2-3 weeks ahead
of maturity which affects both yield and
quality. A disease susceptible hybrid may
not be suitable for silage if it is killed 2-3
weeks before a custom harvester gets to it.
Fungicides are labeled for corn production
and should be used if disease is detected just
prior to silk/tassel stage. Follow all label
restrictions for use of fungicides on corn for
the various uses.

David Wright

Corn for Ethanol Production

It will be necessary to manage corn in
Florida and the Deep South to decrease
aflatoxin when used for ethanol since the
production of DDG S (dried distillers grains
with solids) concentrates not only the
protein but also the aflatoxin. When ethanol
plants make ethanol, they use only starch
from the corn. The remaining nutrients -
protein, fiber and oil are the by-products
used to create livestock feed called DDGS.
Generally, the protein content as well as
aflatoxin levels will be increased 3 fold.
Therefore, aflatoxin levels of corn should be
no more than 5 ppm when delivered for
production of ethanol. A third of the grain
that goes into ethanol production comes out
as DDGS. Each bushel of grain used in the

ethanol-making process produces 2.7
gallons of ethanol; 18 pounds of DDGS and
18 pounds of carbon dioxide. DDGS are
high in yeast proteins, energy, minerals and
vitamins which are an excellent digestible
protein and energy source for beef cattle.

David Wright

What Is Too Early to Plant Corn?

Corn can be planted from early February in
north Florida through early August if proper
hybrids and management are used. Corn
planted in early February in north Florida
usually requires about 70-75 days from
planting to start of silk/tassel period. This
may be as short as 45-50 days for corn
planted in May or June. Therefore, slower
growth can be expected from early planted
corn and nitrogen applications should be
made depending on the amount of uptake
expected by the crop. Weeds may emerge
later on early planted corn and management
should be adjusted to control a late flush of
weeds. Our experience is that aflatoxin is
not influenced to a great deal by planting
date and if anything is less with late
planting. Harvest date, shuck coverage and
insect control may have more influence on
aflatoxin than other factors. Most of the
corn planted in February can be harvested
sometime in July high moisture.

David Wright

Corn Nitrogen Use and Prices

Corn is a high user of nitrogen compared to
many row crops. Irrigated corn normally
requires between 180 to 220 lbs/A to make
high yields when applied in split
applications and banded on the early
applications. This rate is double of what is
used on cotton and wheat. Prices of
nitrogen have risen over the past few years
due to the increase in natural gas which is
the base for nitrogen production. Some

nitrogen materials are cheaper than others
and should be investigated prior to buying.
Generally the liquid fertilizers (28-0-0-5, 32-
0-0, 18-0-0-3, 24-0-0-3) are from 5 to 14
cents per pound cheaper than ammonium
nitrate and urea. Ammonium nitrate is
usually the most expensive followed by
urea. The lower analysis liquid fertilizers
give similar plant responses at similar N
rates to other fertilizers but more material
handling is required. Liquid fertilizers may
be pumped instead of handling dry material
and may be put through irrigation systems.
A 32% nitrogen solution contains about 45%
ammonium nitrate, 35% urea, and 20%
water by weight. Maximum solubility is
obtained at this ratio and crystallization
(salting-out) occurs at 32 degrees F.

David Wright

Ryegrass Knocked Out

Ryegrass takes a hard hit from warm
temperature wave affecting Florida in
December and January. Several pastures
planted to ryegrass in the central and north
east region of the state and some in the
Northwest (Pasco, Hernando, Sumter,
Osceola, Brevard, and Orange counties),
were reported with a severe blight. In many
cases, the outbreak occurred after the second
nitrogen fertilizer application to an
apparently healthy, green and lush ryegrass
stand.

The unusually mild winter with night
temperatures in the 50-60 F and day
temperatures in the 60-70 F or higher are
most favorable for development of the foliar
disease and incidence of pest insects. The
devastating sudden blast was in part
associated with fungal leaf diseases and in
part with insect damage. Samples were
positive for 'gray leaf spot' (Pyricularia
grisea) and 'leaf and crown rot' (Bipolaris
spp.); however, no pathogens were found in
the root system. The thatch layer created by
the rotting of ryegrass leaves produced ideal

conditions for looperss' (Mocis) and 'true
army worms' (Pseudatelia unipuncta) which
were found in excessive numbers, feeding
on new growth and very likely responsible
for the weakening of the root system and
severe blight of the grass.

If not under total pasture stand loss, most
ryegrass cultivars will recover rapidly
following the onset of cold temperatures.

What control practices can be implemented?

* Under unpredicted warm conditions and
when under a mild winter, avoid the
application of high nitrogen fertilizer
rates and N sources that are ready
available such as 'urea'.

* Try to use the forage when leaf spots
first appear to avoid the build up of
succulent tissue.

* Do not mow or graze the stand too short.
Nevertheless, you need to avoid forming
a thick thatch of material that would
favor plant disease conditions.

Yoana Newman

Glyphosate Resistance Still Increasing

Cotton producers have been using
glyphosate for weed control for many years
now. Though once thought of as a herbicide
that would never lose effectiveness, we now
know that previously susceptible weeds can
and will become resistant to glyphosate.

In 2000, the first documented case of
glyphosate resistance in the US was
discovered in Delaware. Although
horseweed was the first resistant weed, it
was soon revealed that it would not be the
last. Since that time, 6 additional glyphosate
resistant weeds have been found. These
weeds include 2 ragweeds (common and
giant ragweed), 2 pigweeds (Palmer

amaranth and common waterhemp), and 2
ryegrasses (Italian and rigid ryegrass).

Although no glyphosate resistant weeds
have been found in Florida, considering the
national trend, it is possible (if not likely) to
occur here as well. It is critically important
that we do not rely on glyphosate for total
weed management in any cropping system
for extended periods of time. In corn, the
use of atrazine and preemergence grass
control herbicides will provide a great weed
control and resistance management
advantage. Likewise, preemergence grass
herbicides and residual products at layby
will be greatly beneficial in cotton. It is true
that adding alternative herbicides will
increase the expense of the production
system. However, managing resistant weeds
is much more troublesome, time consuming
and expensive than a resistance prevention
strategy. A pro-active resistance
management strategy employed now will
pay great dividends in the future.

Jason Ferrell

Am I in Compliance with FDACS
Pesticide Law?

This question should lurk in the back of
one's mind prior to an FDACS inspector
showing up at your establishment and not
after their arrival. The UF/IFAS Pesticide
Information Office has prepared the
informative interactive tutorial, "Surviving
the FDACS Bureau of Compliance
Monitoring Inspection" that helps you
prepare for when that day comes. Know
what to expect, including:

Am I properly licensed?
Am I in compliance with Federal
pesticide recordkeeping laws
according to:
o The use of restricted use
pesticides?

o The use of any pesticide, if
the Worker Protection
Standard is in effect?
Are my storage and mixing/loading
sites up to speed?
Are my applicator employees in
compliance with label directions?
Is my establishment in compliance
with the major provisions of the
Federal Worker Protection Standard,
including:
o Decontamination sites and
supplies?
o Central information display?
o Worker/handler training and
documentation?
o Employer information
exchange?
o Worker/handler notification
of applications?

The page below provides contact
information for the Pesticide Information
Office in case you need technical assistance
or want to give feedback. Macromedia Flash
Player is required for viewing the tutorial.
Visit the Pesticide Information Office's
CEU Modules page for information about
downloading this free software. To view the
tutorial at no cost, see:

http://pested.ifas.ufl.edu/ceu modules/for review
w/Surviving FDACS Inspection/player.html

This tutorial was also approved by FDACS
for 1 CEU credit for those currently certified
as restrictive use pesticide applicators in the
following categories: Aerial, Ag Row Crop,
Ag Tree Crop, Soil and Greenhouse
Fumigation, Forestry, Ornamental & Turf,
and Private Applicator. For those who
would like CEU credit, they should contact
the IFAS Extension Bookstore at 1-800-226-
1764 or http://IFASbooks.ufl.edu. The cost
for the CEU credit is $20. The Bookstore
currently has nearly 20 different interactive
web-based tutorials that are approved for
CEU credit in various categories; each
costing $20.

These presentations were produced in
cooperation with the Florida Department of
Agriculture and Consumer Services.

Fred Fishel

High Nitrogen Requiring Crops and Soil
Ph

High nitrogen applications tend to reduce
the soil pH. All commonly used sources of
nitrogen are acid forming and will require
monitoring of the soil pH to keep it at levels
suitable for row crops. Ammonium sulfate
or nitrogen solutions with sulfur have a
higher calcium carbonate equivalent per ton
and are more acid forming than ammonium

nitrate and urea or solutions. Soils can be
limed at this time of year and still get
benefit. If soils are very acid, it is best to
apply it several months in advance of
planting but reactions begin to occur
immediately. For those growers who use
minimum tillage and strip tillage, surface
applications are acceptable. Long term no-
till plots are still producing good yields of
various crops after 30 years. A high calcium
and phosphorus layer can develop in the top
2-3 inches after many years of surface
applications of fertilizer and lime.

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
products.
Prepared by: J.M. Bennett, Chairman; J.A. Ferrell, Extension Agronomist ii, i, .i. 1 l ..IIn F.M. Fishel, Pesticide Coordinator
.l.h I, ,,1 .I., Y.C. Newman, Extension Forage Specialist .. ,II ..I,. i D.L. Wright, Extension Agronomist (dlw@ifas.ufl.edu).

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