Agronomy notes
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Permanent Link: http://ufdc.ufl.edu/UF00066352/00138
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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
Publication Date: August 2011
Subjects / Keywords: Crops and soils -- Florida   ( lcsh )
Crop yields -- Florida   ( lcsh )
Agriculture -- Florida   ( lcsh )
Agronomy -- Florida   ( lcsh )
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government publication (state, provincial, terriorial, dependent)   ( marcgt )
periodical   ( marcgt )
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General Note: Description based on: January 1971; title from caption.
Statement of Responsibility: Florida Cooperative Extension Service, University of Florida, Institute of Food and Agricultural Sciences.
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Resource Identifier: aleph - 000956365
notis - AER9014
System ID: UF00066352:00138


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Agronomy Notes Aug 2011 Volume 35:8 Features: Forage: Scout for Caterpilla rs ..............................................Page 4 Berseem Clover .........................................................Page 5 Grazing Lands New Publication ...........................Page 7 “Agronomy Notes” is prepared by: Maria Ga llo, Chair and Y. Newman, Extension Forage Specialist (ycnew@ufl.edu); J. Bennett, Cro p Physiology (jmbt@ufl.edu); J. Ferrel, Exte nsion Weed Specialist (jferrel@ufl.edu); F. Fish el, Pesticide Information Officer (weeddr@ufl.ed u); D.C. Odero, Extension Weed Specialist (dcodero@ufl.edu); D. Wright, Extension Agronomis t (wright@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. The Institute of Food and Agricultural Scienc es (IFAS) is an Equal Employment Opportuni ty-Affirmative Action Employer authorize d to provide research, educational information and other services only to indi viduals and institutions that function without regard to race, color, sex, age, handicap or national origin. For information on obtaining other extensi on publications, contact your coun ty Cooperative Extension Office Florida Cooperative Extension Service/Institute of Food and Agricultural Sciences /University of Florida/Millie Ferrer-Chancy, Interim Dean. Miscellaneous: Weeds and Pesticides: Palmer Amaranth Wiper ........................................Page 7 Chemical Fallow on Muck Soils ............................Page 8 Maneb Registration Update ....................................Page 9 Calendar ................................................................Page 9 Crops: Calcium on Peanuts .................................................Page 2 Square Shed in Co tton .............................................Page 3 Daily Water Use by Agronomic Crops.......................Page 6


4 2 Crops Dr. David Wright, Extension Agronomist North Florida REC, Quincy wright@ufl.edu Calcium on Peanuts Nutrient needs of peanuts are less than many crops that are commonly grown in Florida. Calcium (Ca) needs are especially high for peanuts and the fruit develops from nutrients ab sorbed directly from the soil rather than from nutrients transported from roots to s hoots and back to the fruit, which is the case for most crops. Calcium deficiency results in high incidences of pod rot and unfilled pods called “pops”. This defici ency results in low yields, low grades, and poor germination. Relati vely high concentrations of Ca are needed in soil solu tion with critical Ca absorption period beginning about 20 days after the entran ce of the peg into the soil and may extend for up to 2 months. Since peanuts are often grown on sandy soils, whic h are drought prone, there is a limited ability of these soils to replenish the soil solution Ca. Heavier soils and irrigated soils are better able to supply the needed Ca for proper uptake. The Ca needs are primarily for pod and seed development not for growing a healthy plant. Test soils and apply the needed am ounts of Ca for good yields and quality. Ca can be supplied from various sources including dolomite (22% Ca and 11% Mg), hi-cal lime (32% Ca and 3% Mg) and gypsum (23% Ca and 17% S). Gypsum is a fairly soluble source of Ca and does not incr ease pH while providing Ca for peanuts. If the pH of a field is low prior to planting peanuts, use hi-cal lime as it changes pH qui cker than dolomite even though final yield is usually not impacted. Peanuts with pegs just entering the soil and a critical time for high Ca levels in the soil Photo by David Wright Impacts of dolomite vs. calcite lime on pH change over time when liming a low pH soil. G. Stevens, UMO


4 3 Crops Dr. David Wright, Extension Agronomist North Florida REC, Quincy wright@ufl.edu Small squares of cotton that aborted due to stress of dry weather Photo by David Wright Square Shed in Cotton Significant yield potential is lost by premature shedding of squares and y oung bolls. Several factors influence square and boll shed and these include water stress, high temperature, nutrient deficiencies, disease and insects. Anything that results in a decrease in photosynthates will increase s quare and boll shed. In general, younger squares and bolls have a higher shed rate due to hormonal balance while bolls 14 days old and older seldom shed. Therefore, it is important to control as many stress factor s as possible during the first 3-4 weeks of bloom so that an early crop is set which may require fewer inputs and re sult in an earlier harvest. After a period of drought, a rain may occur and growers will notice a significant fruit sh ed as noted in the picture below. This is a common occurrence in most years and should not be a big concer n. Cotton blooms over a period of 8 weeks in July and August often undergo stress during this period. It is desirabl e to set most of the crop in the first 3-4 weeks to prevent excessive vegetative growth which makes for more difficult management a nd harvest. In the far west, it is common to make 4 bale cotton per acre while 23 is more common under good growing conditions in the Southeast. Rain in open bolls can cause fruit shed due to lack of pollination which often occurs in July and August in Florida while cotton grown in Arizona will only have water from furrow irrigation in most years.


4 Forages Dr. Yoana Newman, Extension Forage Specialist ycnew @ufl.edu 4 Scout for Caterpillars (Loopers and Armyworms) With the onset of rains and end of su mmer approaching be scouting for caterpillar presence, armyworms ( Spodoptera sp .) and loopers ( Moscis sp ). The best time to check (and to spray) for these inse cts is either early in the morning or close to sunset, at which time they are most active. By walking your pastures frequently you will be able to detect their presence when they are small and easy to control. When the grass has moisture build up, —if these pests are present they will fall on your rubber boots allowing to detect when they are in an early stage. A product like Dimilin 2L (which is an insect growth regulator that disrupts the normal molting proce ss of the insect larvae) w ith residual effect is recommended only when the worms are small (1/2 inch or smaller) and before populations build Although th is product is effective, due to the mode of action, Dimilin 2-L is slow to control, and si gns of control with this product may not be seen until 5 to 7 days after treatment. If needing to control worms in less than a week other products should be used (see Table below). If infestations are already in place try grazin g the affected area before treating. Fo r additional options, see table below: Product*, ** Rate (Product per acre) Restrictions (waiting time prior to utilization) Maximum number of applications Malathion 57% EC 1.5 to 2 pints per acre None No restrictions Sevin XLR 1 to 1.5 quarts/acre 14 days for hay or grazing Two (2) or less per year Lannate LV to 3 pints per acre 7 days for grazing 3 days for haying No more than 4 applications per year Dimilin 2L 2 fl oz per acre/cutting No restrictions for grazing 1 day for hay No more than 6 fl oz per year. Cannot apply more than 2 fl oz per acre/cutting Tracer 1-2 fl oz/acre 3 days for hay or until it has dried if grazing Baythroid XL 2.6-2.8 fl oz/acre none No more than 4 applications per year B.t. See label none none Coragen 3.5-5.0 fl oz/acre None No more than 4 applications per year Karate 2.6-3.4 fl oz/acre 0 days for grazing 7 days for haying No more than 3 applications per year Mustang 3.0-4.0 fl oz/acre 3 days (hay or grazing) 7 days for harvesting seed No more than 5 applications per year This information is for preliminary planning purposes only. Be sure to always read and follow pesticide labels and guidelines for any product you plan to use. ** adapted from Sprenkel and Buss, 2011. Looper (Moscis spp.). Photo by Yoana Newman. Fall Army Worm, Adult (left) and Larvae (right). Photos by Lyle Buss.


4 Forages Dr. Yoana Newman, Extension Forage Specialist ycnew @ufl.edu 5 Berseem Clover Berseem clover ( Trifolium alexandrinum ) is a cool-season annual legume, also called Egyptian clover, is a fast upright-growing, very palatable legume option for wet areas in Florida. This legume is adapted to the southernmost areas of the US, and was introduced in the state in the early 1950s. The early literature presents berseem as the fastest winter growth legume of more than 50 species tested in the Fo rt Pierce area. The main uses include green manure, greenchop, and grazing. This clover comes from the Nile Delta in the Mediterranean where it has been used as a green manure crop fo r hundreds of years—Berseem tolerates poor drainage and relatively high soil salt content, which makes it a good candidate for many areas throughout Florida, particularly central and south. Although Berseem does not have high cold tolerance since the foliage will freeze, it shows full and quic k recovery from cold snaps (upper 20s), if they are not prolonged. The varieties that are commercially available are Bigbee, and CW 9092. Commercial innoculant for white clover works well on this legume. Varieties Bigbee and CW 9092 have perform ed well on trials conducted in central Florida in the last couple of years. Production is between 2500 to 5000 lb/acre and 2 to 3 cuttings can be obtained depending on the year. For additional information visit the Forages of Florida website at http:// agronomy.ifas.ufl.edu/ ForagesofFlorida/ Top: Berseem clover flower closeup, photo by C.G. Chambliss. Bottom: Berseem clover foliage, photo by Y.C. Newman


4 6 Daily Water Use by Agronomic Crops: Potential Evapotranspiration (ET) Rates are Available from the IF AS Florida Automated Weather Network (FAWN) The IFAS Florida Automated Weather Network, FAWN, located at http://fawn.ifas.ufl.edu/ provides a valuable source of weather information from many locations across the state of Flor ida. In addition to extens ive real-time and archived raw weather data, the FAWN site has some other useful data that are computed from the collected weather data at each location. One example is potential evapotranspiration (ET) rates of crops, a useful input for determining irrigation needs for a crop. The table below, extracted from the FAWN site, shows potential rates of evapotranspiration (ET= crop water use) for a typical, but non-specific crop over a 7-day period in mid July at various locations across Florida. These potential ET values were computed from weather data (collected at FAWN sites) usi ng the Penman-Monteith equation. Potential ET will vary from day to day as a result of changes in environmental conditions (light intensity, relative humidity, wind speed etc.). A 7-day total potential ET is also given in the table. Potential ET values in the table are given in units of inches/day and are representative of water use for crops that are wellwatered (not water stressed) and have a complete ground cover (that is, leaves completely cover the ground surface; rows are fully overlapped so that if one looks down on th e crop the only thing one sees are green leaves – there is no exposure of the soil surface.). Potential ET rates do not vary a great deal over the various loca tions across the state during the month of July (it’s hot and humid throughout the state during the summer months), alt hough during this 7-day period shown above potential ET seemed to be a bit higher in S. Florida. Some of the lower daily values in the above table are most likely a result of cloudy days, o r days when thunderstorms may have occurred. While the numbe rs in the table represent potential ET for a non-specific reference crop, actual ET rates for crops like corn peanut and cotton may be slightly greater than potential ET rates. And, of course, when determining the amount of irrigation water that need s to be applied to meet daily ET demands, the efficiency of the irrigation system must be considered. Just as an example, let’s use a 7-day total potential ET of 1. 25 inches, an estimated increase of 15% above potential ET for a crop like peanut, and an irrigation effici ency of 75%. This would result in the need for 1.92 inches (1.25 + (1.25 x 0.15)/0.75) of irrigation needed over the 7-day period, assuming there is no rainfall That’s 0.27 inches per day, typical values during mid-summer for agronomic crops in Florida. To view tables such as the one shown above, go to the home page of FAWN ( http://fawn.ifas.ufl.edu/ ) and select the following from the tabs at the top of the home page: Fawn Tools Irrigation Evapotransp iration To view a 14-day graph of potential ET values for a particular location: Select Location Go Computed Potential ET values can be helpfu l in estimating how much irrigation wate r to apply during periods when supplemental water is required to keep crops free from water stress. Location 13Jul 14Jul 15Jul 16Jul 17Jul 18Jul 19Jul 7 Day Total Daily Avg in inches & (gals/acre/day) Jay 0.21 0.19 0.13 0.1 0.05 0.19 0.22 1.09 0.16 (4239) Marianna 0.19 0.17 0.08 0.06 0.1 0.2 0.21 1.01 0.14 (3923) Quincy 0.2 0.18 0.1 0.07 0.1 0.2 0.21 1.07 0.15 (4139) Alachua 0.19 0.18 0.12 0.11 0.19 0.18 0.18 1.15 0.16 (4457) Ona 0.18 0.13 0.16 0.18 0.2 0.18 0.2 1.23 0.18 (4756) Clewiston 0.21 0.19 0.2 0.21 0.16 0.17 0.21 1.35 0.19 (5241) Crop Physiology Dr. Jerry Bennett, Crop Physiology jmbt @ufl.edu


4 7 Palmer Amaranth Wiper Palmer amaranth continues to be problematic in peanuts acr oss the southeast. This season has been particularly difficult considering that many non-irrigated fields didn’t receive enough early-season rainfall to activate the preemergence herbicides. Now that the few postemergnece herbicides have been used, there are limited options for the remaining weeds. Fortunately, Gramoxone Inteon has been registered for use in wiper applicators. These wiper-applicators can be very effective, but success is not guaranteed. For these applications, you simply must get enough herbicide on the plant to provide a lethal dose. Though this is common-sense and seems easy to achieve, it can be more difficult than it sounds. Below are a few tips to help maximize success. The herbicide should be mixed as a 50% solution. Ground speed s should be kept to a minimum. Experience has shown that speeds greater than 5 mph can result in reduced control. For optimum performance, 50% of the plant should be wiped. However, these high rates of Gramoxone Inteon (50% solution) has been shown to translocate thr ough the plant. If a full 50% of the Palmer amaranth can’t be wiped, the application can still be effective. Roller and sponge applicators have proven to be the most consistently effective. These applicators work best because they are simply capable of wiping more herbicide on each plant. If using a roller-applicator, carefully watch roller speed. Fast er roller speeds allow you to drive faster and cover more acreage. But, faster roller speeds can sling herb icide solution and cause ex cessive peanut injury. Dense patches of weeds will require slower ground speeds if ad equate amounts of herbicide are to be applied to all the weeds. To determine the best speeds, some growers have begun adding foamer (such as used for foam markers) to the spray tank. The foam allows the driver to easily see how much herbicide is being applied to the weeds (due to the presence of the foam) and speed can be compensated quickly. Though using a roller takes time and te chnique, it can be a highly effective way to remove late-season weeds. Weed Science Dr. Jason Ferrell, Extensio n Weed Specialist jferrell@ufl.edu Forages Dr. Yoana Newman, Extension Forage Specialist ycnew @ufl.edu “Conservation Outcomes from Pastureland and Hayland Practices” Grazing Lands New Publication Look for the upcoming publication “Conservation Outcomes from Pastureland and Hayland Practices” by CEAP. The Conservation Effects Assessment Project (CEAP) is a multiagenc y effort that started in 20 03 to evaluate published research to determine if outcomes desired from conservation prac tices used by private landowners are supported by science. The Grazing Lands component of the CEAP National Assess ment (CEAP-Grazing Lands) will quantify the environmental effects of conservation practices used on pastureland and rangeland. Results from CEAP will help policy makers and program managers implement existi ng and design new conservation programs to more effectively and efficiently meet the national goals. In addition, CEAP will identify ga ps in scientific knowledge and recommend ways to build a timely science base for conservation You can find additional information on the CE AP National Assessment: Grazing Lands at http://www.nrcs.usda.gov/technical/nri/ceap/grazing.html


8 Weed Science Dr. D. Calvin Odero, Extension Weed Specialist dcodero @ufl.edu Chemical Fallow on Muck Soils Weed pressure in fallow sugarcane fields in south Florida has increased following recent rainfall. Growers have traditionally used mechanical cultivation to manage weed populations during the fallow period prio r to sugarcane planting later in the year. Fallow fields are also flooded to control weeds in addition to managing wireworms. With increasing fuel costs and soil subsidence, chemical fallow can be a practical and economical option for weed control during the fallow period. Chemical fallow is the use of herbicides instead of tillage to control weeds on fallow land. Chemical fallow can be considered a form of conservation tillage, which is an integral component of sustainable agriculture in reducing both input costs and soil loss. Most chemical fallow systems use foliar-applied herbicides. Several formulations of glyphosate, the foundation of these programs is used alone or combination with other herbicides. Most formulations of glyphosate contain some surfactant. The need for additional surfactant when using glyphosate should be base d on the quality and amount of surfactant present in the formulation. It is important to always consult the label for specific info rmation on the need for surfactants and other adjuvants. The number and rate of gl yphosate applications in fallow fields should be based on weed pressure present in the field. Single glyphosate application can made at 1 to 2 qt/A. Multiple a pplications of glyphosate will be more effective in controlling difficult to contro l weeds such as bermudagrass during the fallow period. Glyphosate can tank mixed with 2,4-D at 1 qt /A or graminicides such as Select Max and Poast at 8 fl oz/A and 2 pt/ A, respectively for improved efficacy. It is important that herbicide applica tions be made before weeds produce seeds which can be a source of re-i nfestation in subsequent seasons. Photos: 1. Cultivated fallow field in the Everglades Agricultural Area. 2. Flooded fallow field in the Everglades Agricultural Area. 3. Fallow field following glyphosate application in the Everglades Agricultural Area Photos by Calvin Odero


4 9 Maneb Registration Update EPA is revoking all the tolerances for the fungicide maneb with expiration/r evocation dates that provide sufficient time to use existing stocks of the canceled registrations for the last food uses of maneb in the United States. This regulation is effective July 12, 2011. Based on the previous comments received, the Agency agrees that there is a need for more time to exhaust existing stocks of mane b. Therefore, EPA is revoking the tolerances for maneb in 40 CFR 180.110 with the expiration/ revocation dates of December 31, 2012. The Agency believes the extended time is sufficient and consistent to allow users to exhaust exis ting stocks and allow sufficient time for passage of treated comm odities through the channels of trade. Objections and requests for hearings must be rece ived on or before September 12, 2011. Under the Federal Food, Drug, and Cosmetic Act (FFDCA) section 408(g), 21 U.S.C. 346a, any person may file an objection to any aspect of this regulation and may also request a h earing on those objections. Y ou must file your objection or request a hearing on this regulation in accordance with the instructions provided in 40 CFR part 178. Pesticides Dr. Fred Fishel, Pesticid e Information Director weeddr @ufl.edu Calendar To follow the link, press “Ctrl” and put cursor over link, and “click.” Aug. 29EPAF (Extension Professionals) Annual Conference Orlando, Fl Sep 1 FL. http://epaf.ifas.ufl.edu/ Aug. 25 Integrated Pest Manageme nt Field Day for Pasture Management Lake City, FL. http://columbia.ifas.ufl.edu /documents/IPMFlyerAugust2011.pdf Oct. 3-5 Southeast Herbicide Applicator Conference Panama City Beach, FL http://conference. ifas.ufl.edu/sehac/index.html Oct. 16-19 American Society of Agronoy Annual meeting, San Antonio, TX https://www.acsmeetings.org