Title: Agronomy Notes
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Permanent Link: http://ufdc.ufl.edu/UF00066352/00110
 Material Information
Title: Agronomy Notes
Series Title: Agronomy Notes
Physical Description: Serial
Creator: Agronomy Department
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date: March 2009
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Bibliographic ID: UF00066352
Volume ID: VID00110
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: alephbibnum - 000956365


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IFAS Extension

Igronom y Notes

Volume 33:3

Contestant in the Florida
State Fair in Tampa.
Photo by Tyler Jones,
UFIFAS Communications



Pasture Management: Getting the
Most for the Least ................................................ Page 2
Good Bahiagrass Seed for Pastures ....................................... Page 3
Can I Afford to N Fertilize Pastures? ................................. Page 4

Weed Control

Split Applications of Nitrogen on Wheat ..............................Page 4
Organic Arsenicals Agreement ....................... ..................... Page 6
Minimize Nutrient Use by Placement .................................... Page 7


Management of Crops in a La Nina Year .............................. Page 5
Critical Water Use Times for Crops ....................................... Page 5
Crop Response to Rotation .......................... .................... Page 7
Calendar, Field Days & Other Resources .............................. Page 7

March 2009

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.

Agriculture commodity pricing has been on a rollercoaster for the last two years. Crop prices have
achieved record high levels and acreage has soared. To counter the increased demand, fertilizer prices
have doubled at least twice along with fuel prices. Not a big deal when growing $5 per bushel, but this
dramatically impacts the cattle producer since beef prices have hardly moved.

So how can we manage pastures to maximize productivity while minimizing cost?

Essentially, we have five options: 1. Spray herbicides
2. Fertilize
3. Spray and fertilize
4. Mow
5. Do nothing

Let's examine the cost benefit of each of these options.
The chart (figure 1) shows that spraying 2,4-D
(1 qt/A) or applying 34 lb of nitrogen will
Increase grass yield by 230 to 350 pounds per
acre. Applying nitrogen and herbicide together
more than doubles grass production. However,
if fertilizing and spraying is too expensive,
which should we chose? Depending on what
source of fertilizer is used, 34 lb of nitrogen can
cost between $20 and $40/A. On the other hand,
a herbicide plus application cost will run
between $8 and $25/A, depending on which
herbicide and application rate is used.
Considering that either of these will improve
grass yield, a herbicide application is likely to
be the most cost effective.

SObviously we know that pastures will need
fertilizer and lime to continue productive
growth. So when do we do it? Weed control in
pastures will generally not be required every year. So, clean up the weeds in year 1 and plan to start on a
fertility program in years 2 and 3. This process will increase the competitiveness of the grass and, in turn,
suppress weed growth. A healthy pasture is the best form of weed control. But we must remove the
weeds present before this process can occur.

Mowing is another technique commonly used by pasture managers. Depending on equipment size
and driver skill, mowing can cost between $8 and $15/A. Is this money well spent? Figure 2 indicates
that mowing will generally not result in improved grass production. This is because mowing rarely kills
weeds, but rather just sets them back and delays their regrowth. Therefore, mowing can cost almost as
much as a herbicide application, but may not provide any weed control or improved grass production.
With mowing it is important to remember that fuel no longer cost $0.75/gal. At one time mowing was
very inexpensive and any benefit from it was gain. But, we simply don't have the luxury of performing
cheap mowing anymore.

Lastly, we can always choose to do nothing and let the grass and weeds compete.

Agronomy Nofes Pae

Cnine on nex pae.

Like all ventures, low investment generally provides low return. This method can be profitable for
producers that use very low stocking rates. But, normal herds will be hurt by this process and weight gain
will be slow and body condition will suffer. With marginal investments, the amount of additional weight
gain the animals will achieve can easily pay for itself.

We are all aware that the best way to maximize grass production and cattle performance is to manage our
pastures with proper fertility, mowing,
and herbicide applications. But, if
performing all these simultaneously is
not affordable, we must choose a
strategy to maximize our resources. It is
likely that herbicide use is the most cost
effective way to initially improve grass
Production. After weeds are controlled,
330 a good fertility program will be needed.
Lastly, large scale mowing will
generally cost more than it returns. It
may be necessary to limit mowing and
reinvest the savings in other areas.
The chart on the previous page (Figure
41 1) shows the Influence of herbicide (1
qt/A 2,4-D), nitrogen (34 lb/A of N),
and herbicide plus nitrogen fertility on
grass growth on a field infested with

This chart above (Figure 2) shows the influence of herbicide application and mowing on grass growth on
a field infested with ragweed and wooly croton.

Dr. Jason Ferrell, Extension Weed Specialist Dr. Brent Sellers, Extension Agronomist
jferrell@ufl.edu bsellers@ufl.edu

Y Bahiagrass Seed for Pastures

Seedbed preparation and fertilizer cost are too high to afford planting poor seed.

If you are planting seed that is not tested you don't have any means of knowing how much 'quality seed'
you are getting. Seed quality information usually comes on a tag attached to the seed bag.

There are two things you need to pay attention when buying seed: the purity of your seed and the
germination. The first one refers to how clean is your seed, or stated differently, how much seed of the
pasture species you want is there. The second one tells you how many seeds will sprout given optimal
growing conditions. Acceptable ranges for bahiagrass germination are 50 to 60% for Pensacola, 60 to
70% for Tifton 9, and 85 to 90% for Argentine.

Dr. Yoana Newman, Extension Forage Specialist
ycnew@ufl.edu I Agronomy Notes


Normally N is applied to wheat in the first half of February. However, on very sandy soils, N may be
split into two applications. If this is the case, the second application of N should be applied in early
March along with sulfur. Sulfur is critical on sandy sites and will result in higher yields if it had been a
limiting factor. A total of 30-35 lbs/A of S is usually adequate and is less necessary on heavy soils that
have a clay layer near the surface. March is usually too late to consider week control since most adapted
wheat varieties will be headed out in late March or early April.

Dr. David Wright, Extension Agronomist
North Florida REC, Quincy, wright@ufl.edu

Yes, but you need to know how much to apply and when to apply it as the grass is growing.

In the first weeks after planting your pastures, the grass roots are just coming out, and the root system is
not fully developed. Only a moderate amount of N is needed at this time (no more than 25-30 lb N/acre
but not less as you may not be supplying enough, and applying too little might be worst than applying
none as you have to pay for it). A rule of thumb is to apply 30-30-30 lb (N-P2)5-K20) one week and no
later thanl0 days after planting bermudagrass tops. Make sure you have a good weed control program
in place to avoid use of fertilizer by weeds. When your plants are grown and have a full root system you
can add more fertilizer. Putting the smaller amount at planting and a larger dose later in the summer will
maximize yield and efficiency.

If deciding to fertilize an established stand and can only afford to do 1 application, the target is to do
that application when you are more likely to get a response. Too early in the spring or late in summer
are not good options because these are the tails of the growing season; a time when warm-season
perennials are less productive because of
shorter daylength and cooler
60 Nitrogen Fertilizer temperatures
60 53--
Z 554 Prices (cents/ Ib N)
z 50
Test your soil (and plant tissue if dealing
" 40 with an established stand) to make sure
e 30 that all your other nutrients are available
20 m 1 year ago as plants work best and more efficient
10 U January 26, 2009 (more grass for your fertilizer buck)
under balanced nutrition.

,, 00 <3 o With the current upward trends of N
a fertilizer prices and the prospects ofN
P o fertilizer options narrowing, the future
of N supply may be dominated by the
cheaper urea.

Dr. Yoana Newman
Extension Forage Specialist

Agronomy Notes Pa

Management of Crops in a La Nina Year

Historic records show that weather conditions in late winter and spring will be dry in a La Nina year.
Management of crops will change on non irrigated sites with that in mind. Soybean, cotton and peanut
should be planted earlier since it is often difficult to get stands until summer rains begin in late June and
July-a time period that is too late for optimum yields on these crops. If the fields have winter cover
crops, these crops should be killed 5 weeks ahead of planting, or more if possible, to conserve moisture
for the following crop emergence and growth. Dry-land corn should be planted later since it normally
goes through pollination in mid May which is usually a dry month and you need to have adequate
moisture during this critical period for corn. With irrigation, these guidelines are not as important since
water can be applied to get fast and uniform emergence.

Dr. David Wright, Extension Agronomist

Soil moisture monitoring is important for top yields of crops. Recent UGA data compares moisture
equipment to visual estimates. When moisture equipment indicated that corn needed to be watered
irrigation was delayed one, two, and three days each time it called for irrigation. Yield was reduced by
less than 5% with a one day delay, almost 10% by two days delay and by almost 20% with a three day
delay. This will take a 200 bu/A yield potential down to a 160 bu/A crop.

C orn is the most susceptible to water stress of the row crops since it has a 10 day period during
pollination that has to be low stress (usually mid-May a typically dry time). However, corn
requires good moisture during the ear fill period of June and early July to make high yields.

Soybean is very susceptible to damaging nematodes levels and needs water during pod fill
which is late August and September for MG V and September and October for MG VI-VIII.
MG V soybeans normally do better when planted timely with normal summer rainfall patterns
but can vary with time of tropical storms.

C otton blooms over 8 weeks and can set most of the fruit or yield in the first 3-4 weeks and
requires most moisture during bloom time of July and August.

Peanut has a long bloom period and can produce a crop over a long period after long periods of
stress as can cotton and does best on sandy soils. July and August are usually most critical for
high yields of peanut.

Dr. David Wright, Extension Agronomist
North Florida REC
Quincy, wright@ufl.edu

"Agronomy Notes" is prepared by: J.M. Bennett, Chairman and Yoana Newman, Extension Forage
Specialist (ycnew@ufl.edu); B. Sellers, Extension Agronomist (bsellers@ufl.edu); J. Ferrell, Extension
Weed Specialist (j tenel Itul.edui; F.M. Fishel, Pesticide Coordinator (weeddr@ifas.ufl.edu); and D.
Wright, Extension Agronomist (wright@ufl.edu). Designed by Cynthia Hight (chight@ufl.edu.) The Agronomy Notes P
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.

EPA has reached an agreement in principle with the major manufacturers of the organic arsenicals
MSMA, DSMA, CAMA, and cacodylic acid and its sodium salt. This voluntary agreement steadily
removes all organic arsenical pesticide uses, except the use of MSMA on cotton, from the market and
implements new restrictions to better protect drinking water resources. Phasing out these uses is
expected to accelerate the transition to new, lower risk herbicides.

Under the agreement, many uses, including use on residential lawns, will be canceled by the end of this
year. For products used on cotton and products phased out after 2009, new use restrictions and
mitigation measures will be added to increase protections to water resources. Mitigation measures in
the near and upcoming future include:

By mid-March, the registrants must submit voluntary cancellation requests for all uses, other than
the use of MSMA on cotton.
By the end of 2009, many existing uses will be phased out and canceled including use on
residential lawns, forestry, non-bearing fruit and nut trees, and citrus orchards.
Over the next 4 years, uses on golf courses, sod farms, and highway rights-of-way will be phased
out, promoting transition to alternatives.

In the Agency's 2006 Re-registration Eligibility Decision (RED), EPA concluded that all uses of the
organic arsenicals were ineligible for re-registration. Following application, these pesticides convert
over time to a more toxic form in soil, inorganic arsenic, and potentially contaminate drinking water
through soil runoff. At that time, EPA believed that inorganic arsenic also could enter the human food
supply through the meat and milk of animals fed cotton by-products treated with MSMA. In
completing the RED, EPA determined that the aggregate dietary risks from food and drinking water
combined did not meet the food safety standard.

During the last two years, stakeholders have submitted additional data indicating that no residues of
inorganic arsenic are likely to remain in the meat and milk of animals fed cotton by-products that have
been grown in fields treated with MSMA, or in food crops that are rotated with cotton that has been
treated with MSMA. Cotton growers also have documented the increasing spread of Palmer amaranth
or pigweed, a glyphosate-resistant and economically significant pest, which only MSMA controls at

In light of this new information, the agreement allows for re-registration of MSMA use on cotton,
contingent on the development of confirmatory data. If these data are not submitted by the August 2010
due date, or if they do not confirm the current scientific understanding, EPA will proceed to cancel the
cotton use. The Agency is also rescheduling the Registration Review of MSMA to begin in 2013. At
that time, MSMA's risks and benefits will be reevaluated considering any new toxicity information and
the availability of new, lower-risk herbicides that should be entering the market.

EPA will amend the 2006 Organic Arsenicals RED to reflect the provisions of the agreement. Public
comment opportunities will be provided when the Agency publishes Federal Register notices
announcing its receipt of registrants requests for voluntarily cancellation of uses.

Dr. Fred Fishel
Pesticide Information Officer

Agronomy Noes Pag

Minimize Nutrient Use by Placement

With fertilizer prices at or near an all time high, growers are looking for ways to minimize fertilizer
usage while not impacting yield. Fertilizer rates can be minimized by placement of needed nutrients in
the row. Most soil test recommendations are based on broadcast rates of application. Our research
would indicate that P can be cut in half and K by 1/3 if applied in row vs. broadcast applications with-
out loss of yield and there may be a yield increase in dry years if irrigation is not available. This cuts
could result in significant savings while requiring more time and labor. For many years fertilizer was
cheap enough that higher rates could be applied without having to watch for one more thing during the
planting operation.
Dr. David Wright, Extension Agronomist

All crops benefit from proper crop rotations by having
higher yields and requiring less pesticide use and often Good rotations lead to:
less inputs. Some growers have few options in their area
on what crops can be handled by local infrastructure Full use of Water and Nutrients
resulting in growing the same crop in the same fields too
often. Poor rotations results in higher input prices and Less Nematode, and Disease Pressure and
marginal yields for profitability of the operation. Pesticide Use

Response to rotation from most to least responsive: Enhanced Yield and often Quality of
Soybean ~ Peanut ~ Corn ~ Cotton Rotation Crops in Rotation

Dr. David Wright, Extension Agronomist
North Florida REC, Quincy, wright@ufl.edu

March 12-15 Maize Genetics Conference, St. Charles, IL

March 20-21 UF Bee College, St. Augustine, FL Featuring over 40 lectures and
workshops on honey bees and beekeeping. www.UFhoneybee.com

April 4 Performance Horse Short Course, Okeechobee Agri-Civic Center
For those who use their horse for ranch work or competitive events.
8:30am 3:00pm. (863) 674-4092 or horsel@ufl.edu

April 16 Cattle and Forage Field Day, Ona, FL
UF Range Cattle REC, 863-735-1314, ext. 201

May 4-7 UF Aquatic Weed Control Short Course, Coral Springs, FL

June 5-9 American Society for Reproductive Immunology, Orlando, FL

July 20-24 National Conference on Ecosystem Restoration (NCER)
Los Angeles, CA
Agronomy Notes

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