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Agronomy notes
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Permanent Link: http://ufdc.ufl.edu/UF00066352/00098
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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: March 2008
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.
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Resource Identifier: aleph - 000956365
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Full Text

IFAS Extension

loronomy otes

Voeumen 32:3 MarcA 2008

Features ...

Early Planted Corn and Pest Risks Page 9
Forage Potential of Edible Peanut Page 2
Warm Winter andyour Florida
Winter Forages Page 8
Timing of Forage Fertilization Page 10
Implications ofIncreased Soybean
Acreage Page 2
Wood Control
Mexican Prickly Poppy Control Page 3
Pre-emergence Use ofProwl in
Corn Page 6
pH and Pesticide Stability Test
your Mix Page 5
Choosing Crop Rotations When All
Crop Prices Are High Page 6
SWater TestsforpH Page 7

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.

Forage Potential of Edible Peanut

Many farmers are looking into annual peanut as a hay crop. Dr. Dan Gorbet from University
of Florida researched edible peanut for forage production in a 5-yr study. Different cultivars of
edible peanut that included 'Southern Runner' with late leaf spot resistance, were planted in May or
early June without irrigation. Yields averaged
over different cultivars and 5 years were
4200 lb/acre when cut only once, (at 135-140
Sd, just prior to digging), and they were 5800

and again prior to digging). The nutritive
value of the forage was higher at each cut in
the two harvest system with crude protein
ranging from 14 to 19.6%, and digestibility
ranging from 61 to 72%. When cut only
once, crude protein was lower than when cut
r twice and ranged from 12.5 to 14.8%.
Similarly, digestibility ranged from 55.7 to
Peanut 61.3%. This study shows that edible peanut
Photo: National Peanut Board
can be used for forage production with yields
close to 6500 lb/acre which compares
satisfactorily to perennial peanut. One point to keep in mind is that growing edible peanut might
have all the expenses associated with a row crop, but if in emergency situation it will provide quick

Dr. Yoana Newman,
Extension Forage Specialist

Implications of Increased Soybean Acreage

Increased soybean acreage means better scouting for rust- With soybean prices at historic
highs the acreage is expected to increase. With 3 years of intensive research at the NFREC in
Quincy, we know that when rust hits during the early bean set period, yields can be reduced by a
third. Earlier infections could mean even more losses. Some of our cooperative research at NFREC
has shown that a 10% leaf infection by rust can reduce photosynthesis by 75%. Therefore, soybeans

(continued on Page 9)

"Agronomy Notes" is prepared by: J.M. Bennett, Chairman and Yoana Newman, Extension For-
age Specialist ( !i II co lll J.A. Ferrell, Extension Agronomist (i.lcc II., i i.1 i l..lll I
F.M. Fishel, Pesticide Coordinator (weeddr@ifas.ufl.edu); J. Marois (jmarois@ufl.edu); Brent
Sellers, Extension Weed Scientist (bsellers@ufl.edu); and D.L. Wright, Extension Agronomist
(dlw@ifas.ufl.edu). Designed by Cynthia Hight (chight@ufl.edu.) 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.
AgFronosmy Notes P

Mexican Prickly Poppy Control

Mexican prickly poppy (Argemone mexicana), also known as goatweed, Mexican thistle,
prickly poppy, and yellow thistle, is a member of the poppy family. It is an annual or biennial
plant that is found east of the Rocky Mountains, Hawaii, and Puerto Rico. In Florida, it is typi-
cally recognized as 'some type of thistle' until it flowers.

Most believe that Mexican prickly poppy is
a thistle when plants are young due to the
toothed and prickly leaf margins, giving it a
thistle-like appearance (See front page
photo). However, one key difference is that
Mexican prickly poppy exudes a yellowish
milky sap when stems are broken, while
thistles do not. Another difference is in the
flower where Mexican prickly poppy has
relatively large yellow flower (Figure 3)
with 4 to 6 petals, which is quite different
from the flower cluster that is common with
thistles. Like thistles, Mexican prickly
poppy reproduces only through seed produc-
tion. Seeds are enclosed in a relatively large
spiny capsule (Figure 4). Approximately 400
Soft Rush (Bull Rush) seeds can be produced in one capsule.
Photo: Brent Sellers
(continued on next Page)

May 12-14 Southern Pastures and Forage Crops Improvement
Conference, Knoxville, TN

June 1-4 Florida State Horticultural Society and Crop Science
Society of Florida Meeting, Marriott North, Ft. Lauderdale, FL

July 13-17 Caribbean Food Crops Society Meeting
Miami, FL Hosted by UF/IFAS

July 13-15 Southern Peanut Growers Conference
Edgewater Beach Resort, Panama City Beach, FL

Agronomy Notes P

Calendar Dates

Mexican Prickly Poppy Control (cont...)

Key characteristics for recognition:

Stem: Cylindrical, whitish in color and with scattered prickles. When broken, a
yellowish milky sap can be readily observed.

Leaves: Leaves can be up to 8 inches long, and are
typically silvery-green with white veins and
deep regular lobes, the upper surface of the
leaf is smooth, while the underside has a
few prickles along the midrib. The edges of
the leaf are often lined with many prickles. I

Flowers: Flowers are yellow and approximately 2.5
inches in diameter.

Seed: Seeds are produced inside a prickly capsule
measuring at 1.5 inches in length.
Approximately 3 to 6 openings in the F o M
Flowers of Mexican prickly popp
capsule allow the seeds to disperse, but mately 2.5 inches in diameter and
many of the seeds can remain inside the yellow petals
capsule for weeks until wind or animals Photo
shake the plant. Up to 400 seeds can be
enclosed by a single capsule and the seeds may stay dormant in the soil for
many years.

Mexican prickly poppy is poisonous to livestock.
However, there are very few cases of poisoning related to
this plant because it is not readily eaten. However, plants
in hay have been a source of poisoning. Seeds are often
considered the most toxic, but the entire plant contains
toxic properties as well.

Although this weed is common throughout all
Florida, it is typically not a wide-spread problem weed.
But for those who wish to control it, 2,4-D or WeedMaster
(or other products containing 2,4-D + dicamba) are the
most effective and economical herbicides for control. The
application rate for each herbicide is 3 pt/acre for
broadcast applications. If spot spraying is necessary, a 3%
solution of either 2,4-D or 2,4-D + dicamba in water is
appropriate. Remember, it is best to treat a younger plant,
especially before seed set occurs to ensure that seeds are
not added to the soil seedbank.

Brent A. Sellers, Extension Weed Scientist
Range Cattle REC, Ona

beea capsues o0 Miexican pncriy poppy are
approximately 1.5 inches long with numerous
spiny prickles.
Photo: Brent Sellers

Ajrosmey Notes A

pH and Pesticide Stability Test Your Mix

This past year, several extension agents contacted the Pesticide Information Office to in-
quire about pesticide instability when mixed with alkaline water. Several relevant factors
concerning the phenomenon have been known for a number of years:
> It is known that, in general, there are problems of chemical breakdown with
certain families of pesticides the carbamate and organophosphate insecticides
are most notorious.
> When mix water has pH values of 7.5 and higher, there should be concerns
particularly if using to dilute pesticides known to undergo this problem.
> Leaving a mixture in a tank for an extended period of time, or even overnight
and less, for some pesticides, can render them ineffective.
> A water pH of 5.5 to 6.5 is ideal for most pesticides.
> Acidifying agents are commercially-available that will acidify the pH of the
spray solution, if needed.

What, apparently, is not widely known is how common the occurrence of this being a
problem with pesticide application. We know that we have alkaline water in the state as
the majority of groundwater withdrawn is from the Floridian Aquifer (limestone-based).
In presenting this information to several large commercial applicator audiences this past
fall, an informal survey showed that the vast majority of those applicators had never tested
their water pH. My first and obvious thought was that they could have potential problems
that they had never taken into account. The few applicators who responded positively
mentioned that their water tests showed an approximate pH value of 8. Table 1 shows
some examples of pesticides that can undergo alkaline hydrolysis. The half-life is the time
necessary to lose 50% of its activity

Table 1. Half-life (50% hydrolysis time) of selected pesticides at varying pH values.
Active ingredient pH 6 pH 7 pH 8 pH 9

Azinphos-methyl 10 days 12 hours
Captan 8 hours 10 minutes 2 minutes
Carbaryl 100-150 days 24-30 days 2-3 days 1-3 days
Carbofuran 200 days 40 days 5 days 3 days
Chlorpyrifos 35 days 22 days
Diazinon 70 days 29 days
Dimethoate 12 hours 1 hour
Disulfoton 32 hours 7 hours
Malathion 8 days 3 days 19 hours
Methomyl 54 weeks 38 weeks 20 weeks
Phosmet 1 day 4 hours (pH 8.3) 1 minute (pH 10)

Propargite 331 days 1 day
Trichlorfon 4 days 6 hours 1 hour

Dr. Fred Fishel
Pesticide Coordinator

Agronomey Notes

Corn production is quickly returning to Florida due to the currently high commodity prices. The
vast majority will be Roundup Ready, but we commonly advise corn producers to use a more di-
verse weed management program as a way to reduce risk. One of the most effective and inexpen-
sive programs is Prowl + atrazine followed by glyphosate. Prowl + atrazine will provide broadspec-
trum residual control of grass and broadleaf weeds and allow greater flexibility with the glyphosate

However, many corn producers hesitate to use Prowl because of potential injury. Prowl can cause
moderate to severe root-pruning in corn if the applications are not made correctly. Therefore, the
following conditions should be met to maximize crop safety. 1. Corn should be planted approxi-
mately 1.5" deep to ensure the seed is well below the soil surface. 2. Do not spray Prowl until the
corn has started to emerge. Applying Prowl too early can greatly increase the likelihood of injury.
3. Don't apply Prowl until after a rainfall or irrigation event. Even if the corn is emerged, if the fur-
row has not been settled with rainfall, corn injury is possible.

A Prowl + atrazine combination is a highly effective herbicide combination. If used properly, these
herbicides will control a vast number of weeds and provide weed-free corn for several weeks.

Dr. Jason Ferrell
Extension Weed Specialist

ID Ji S l llS ll 11 11 1D II11 I

When making the decision on what crop to grow on your farm for 2008, many factors have
to be considered in addition to price, and that includes: harvesting and handling facilities, rotation
schemes for future crops, economic risks from inputs, drought tolerance of crops if irrigation is not
available, and how it fits with other crops planned in terms of time and labor for planting, and har-
vest and management throughout the season. Corn usually has to be taken out with high moisture
and should be dried down for top yields and quality. Soybeans, corn and wheat require storage
which has decreased since the 1980's and requires a grain combine which few have been bought
since the late 1970's. All of these factors are important and can make a difference in long term vi-
ability of the farm.

Dr. David Wright, Extension Agronomist
North Florida REC, Quincy

AtomoLmiY Notes P

Water Tests for pH

A water test is the surest means of determining if a problem exists. The IFAS Extension Soil
Testing Laboratory in Gainesville offers a water test to the public for $10.00 per sample. The form
with instructions is available through all county Extension offices or can be printed directly from
the ESTL website (http://soilslab.ifas.ufl.edu). A less reliable, but fast, way to determine the pH
level of water is to test it with test paper. Paper test strips (Figure 1) are the least expensive;
however, they can vary by as much as 2 pH points. A pH meter (Figure 2) will also provide fast
results, but more reliable and consistent readings. Meters are available commercially for as little as
$50 that will measure pH within 0.2 points accuracy. More expensive models have greater
precision and may have the ability to conduct additional measurements such as electrical

Ni.MuEiandul.al I rdbry.. R.LK .h.Y. B]101-ULA
H 2 3 4 5 6 1

pH7 8 9 10 11 12

Fig. 1. Paper test strips Fig.2. pH meter
Photo: Fred Fishel Photo: Fred Fishel


Determining the pH of the spray mix water and adding an acidifier, if necessary, is inexpensive
compared with the cost of losing a pesticide's effectiveness. There are water sources in Florida that
are alkaline by nature, and the addition of an acidifying agent to the spray mix is an easy and
economical way to guarantee maximum results from your pesticide applications. Label statements
similar to this (Photo below) will alert the user of potential problems. More details on this subject
are presented in the following EDIS Document: Water pH and the Effectiveness of Pesticides
http://edis.ifas.ufl.edu/PI193#TABLE 1.

Read all precautions and directions before using Apply this product only as specified on this label
Imidan 70.W is compatible with most commonly used insecticides and fungicides, but is incompatible with alkaline materials such as spray lime, lime
sulfur, and Bordeaux mixtures. These materials will reduce the insecticidal activity of Imidan 70-W.
Insecticidal activity may also be reduced when the spray solution has a pH of 6 or higher. The pH of the spray solution must be corrected by
the addition of a suitable buffering or acidifying agent for optimum insecticidal activity.

Dr. Fred Fishel
Pesticide Coordinator

A mrO y Notes PA

Stunted rye planting in north-central Florida.
Photo: Yoana Newman

I_ _

This was not a good season for winter forages in
general. This year again the culprit is weather. Many calls
and reports this winter have been associated with stunning
of winter crops (rye, ryegrass, and clovers for those that
planted them). We did not observed as many fungal dis-
eases as last year in winter forage grasses but there was a
stunning associated with most of them.

At one location near Gainesville, stunting of red
and crimson clover has been correlated with sting nema-
todes. Sting nematodes are ectoparasitic, meaning they
live in the soil and feed on growing plant root tips. Previ-
ous research with the clovers has focused on root-knot
nematodes and new varieties from Florida have resistance
to these pests.

Warmer soil temperatures favor nematode activity,
generally speaking. With the high temperatures, these cool
-season plants find themselves at the mercy of many pests
that are seizing the opportunity brought by weather related
stress to invade.

Dr. Yoana Newman,
Extension Forage Specialist

Clovers with sting nematode infestation-associated with
warm winter in FL.
Photo: Ken Quesenberry

UFIFLORIDA Keeping Connected
IFAS Extension
For a listing of our site on Insects, Mites Entomology and Nematology
and other topics: newsletter available at
http://pests.ifas.ufl.edu/ http://entnews.ifas.ufl.edu/

Agronomey Notes

(continued from page 2...Implications of Increased Soybean Acreage)

should be scouted when they start blooming and continue into the late pod fill stage. If the dis-
ease is detected, it should be sprayed with a fungicide. Florida will have sentinel plots across
Florida again in 2008 and the information will be posted on the http://www.sbrusa.net website.
The soybean rust pathogen attacks several other legumes in North America but is prevalent on
kudzu throughout Florida. It has been detected every month of 2008 in sites in North Florida
where rains and mild temperatures have kept kudzu actively growing. Leaves of kudzu have
shown that rust spores are still being produced. Wright and Marois

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

I Early Planted Corn and Pest Risks

If corn is planted into cover crops, cover crops should be killed at least 2-3 weeks be-
fore planting or an in-furrow insecticide should be used for control of southern corn root worm,
cutworms, etc. These insects will stay in the soil for a couple of weeks as the cover crop is dy-
ing and then will go to the newly emerged corn for feed-
ing as soon as it has germinated. Early planted corn has
a better chance of avoiding leaf and whorl feeding fall
armyworm as well as damaging disease epidemics dur-
ing its growth period. Planting in early March often re-
sults in high yield and quality. Corn is not very suscep-
J tible to frost since the growing point remains under the
.- soil surface until corn reaches about 12" high. The
vegetative stage of growth can be slow from early plant-
ing but still fares better in most years than when corn is
planted in late March and April. Stink bug should be
controlled when corn starts to silk and tassel because
they will cause considerable damage and may result in
Corn leaf and .tilnkhig eggs. high levels of aflatoxin making it unsuitable for sale for
Photo: David Wright livestock feed or in ethanol production. The problem is
that the aflatoxin would stay with the dried distillers
grain which is used for livestock feed. Wheat and other small grain will be maturing when corn
starts silking which is attractive to stinkbugs. Very little scouting is done on corn at this time
but it will be necessary to reduce aflatoxin levels in corn from Florida if it is to go into the etha-
nol trade.

Dr. David Wright, Extension Agronomist
North Florida REC, Quincy

Agronomey Notes P

STiming of Forage Fertilization

The criteria for fertilization of warm-season forage species is a soil temperature above 70 F or
night temperatures that are consistently 60-65 F. In general, day time soil temperatures will be slightly
lower and will fluctuate less than air temperatures. Soil temperature is the
& t target but it is easier to monitor air temperature readings from night news
7 updates.

SThe time to fertilize warm-season grasses is when the plant roots
are actively growing and able to uptake the fertilizer (soil T above 700F).
With the varying weather patterns is better to target the night air tempera-
ture occurring in a consistent manner for approximately 2 weeks. To rec-
ommend a 'date' could be misleading because of the change we are observ-
ing in weather patterns, and it could be an earlier or later than usual 'warm
,...' year'; in past years this date would have been mid May. If you fertilize
your forage plants too early you are creating a cool-season weed problem
because you will be feeding cool-season weeds and later creating competition for nutrients. Optimum
growth for warm-season plants, in general, occurs at air temperatures in the mid 80s up to 100-1040F.

Dr. Yoana Newman,
Extension Forage Specialist

IAjgromooey Notes Pt