Extension Ag Update
January/February 2004
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Rotate Roundup Ready Soybean with Non-Roundup Ready Soybean

Agronomy Journal, Volume 97, 2005, Larry G. Heatherly, Krishna N. Reddy, and Stan R. Spurlock, http://agron.scijournals.org/cgi/content/abstract/97/2/568

Roundup Ready (RR) soybean cultivars offer increased profits. However, continually using glyphosate is associated with weed resistance to glyphosate. Weed management in RR and non-RR soybean involves two approaches: using soil-applied pre-emergent followed by foliar-applied post-emergent herbicides (PRE + POST), and using POST-only herbicides. Scientists compared weed populations, yields and net returns from continuous and rotated RR and non-RR soybean production. RR cultivars using POST-only glyphosate were most economical. Net returns for non-RR cultivars were similar between PRE + POST and POST-only treatments. Rotating RR and non-RR cultivars had no significant effect on weed populations and control, soybean seed yield or net return.

Should Endophyte-Infected Tall Fescue Pastures Be Replaced?

Agronomy Journal, Volume 97, 2005. Jun Zhuang, Mary A. Marchant, Christopher L. Schardl, and Courtney Murrell Butler, http://agron.scijournals.org/cgi/content/abstract/97/3/711

Beef and dairy cattle grazing on endophyte-infected tall fescues often develop physiological disorders that reduce animal performance and profitability. To resolve this problem, one could replace endophyte-infected tall fescue pastures with endophyte-free varieties. To evaluate the costs and benefits for replacement, careful calculations are needed. For this study, researchers developed an investment analysis model of renovating existing endophyte-infected pastures with an endophyte-free variety. Empirical results estimated benefits of economic management strategies that have not been previously assessed. Researchers suggested that it may be profitable for farmers to replace endophyte-infected tall fescue pastures with endophyte-free pastures if infestation level exceeds 74 percent.

New Anti-Mastitis Weapon on Tap for Dairy Cows

Jan Suszkiw, ARS News Service, (301) 504-1630, jsuszkiw@ars.usda.gov

Injecting a sugar into cows' udders to mobilize an immune system response may give producers an alternative to antibiotics for fighting mastitis. In trials at the Agricultural Research Service's (ARS) Bovine Functional Genomics Laboratory in Beltsville, Md., scientists Max Paape and Douglas Bannerman showed that injecting cows with the yeast sugar Poly-x reduced mastitis infection at one-twelfth the cost of antibiotics.  Their patent-pending approach is based on prior studies at the lab showing that increasing milk's white blood cell count will prevent infection by mastitis-causing bacteria. When injected into non-lactating dairy cows, Poly-x functions as a kind of bugle call that mobilizes the cells to attack mastitis pathogens.

During the trials, the scientists injected 40 non-milking Holstein cows with Poly-x and 40 with antibiotics. After the cows began lactating again, the scientists checked the animals for signs of mastitis infection. Those with Poly-x had a net gain of five new infections compared to 16 for antibiotic-treated cows, reports Paape.   ARS has applied for patent protection on the Poly-x treatment, and is seeking a commercial partner that can ready it for marketing to conventional and organic dairy producers.

Mastitis is an inflammation of cows' mammary glands that costs the U.S. dairy industry approximately $2 billion annually in both animal and dairy-production losses. Today's control programs include diagnostic testing, herd separation, animal culling, teat dips and antibiotic treatment. The latter, however, can be costly to use as well controversial because of environmental contamination and other concerns. 

Paape and Bannerman see several advantages to using Poly-x as a natural alternative--the lack of residues being one. Expense is another: A tube of antibiotic costs about $2.50, compared to 20 cents for a Poly-x treatment.

Shade Trees Can Protect Forage Plants

Don Comis, ARS News Service, (301) 504-1625, comis@ars.usda.gov

Giving forage plants, as well as animals, some shade from trees could be profitable for farmers, especially those farming marginal lands.  Soil scientist Charlie Feldhake, agronomist Dave Belesky and animal scientist Jim Neel of the Agricultural Research Service (ARS) are in their fourth year of raising lambs on oak and conifer silvopastures, combinations of forages and trees growing together on the same land.  Belesky heads the team of scientists at the ARS Appalachian Farming Systems Research Center in Beaver, W.Va. 

The scientists have found that some plants do better under moderate shade than in traditional open pastures.  For example, Neel found that moderately shaded forage has more protein than forages on open pasture during the heat of July and August. 
Silvopastures also seem to buffer drought and other seasonal extremes.  Feldhake found that this buffering includes helping forage plants warm up about two weeks earlier than usual in the spring and to stay warm enough in late fall to hold off the hard frost for about two weeks. These effects are greatest under conifers.

This means silvopastures could provide another four weeks of forage growth and grazing time.  The extra warmth in cool seasons comes from thermal radiation trapped and returned by the tree canopy. 

The silvopastures are designed carefully, from the size of the trees to the amount and quality of sunlight allowed to reach the forest floor.  The sites have instruments to monitor light, soil temperature, wind speed, precipitation and soil moisture. The amount of light-buffering from tree shade has to be just right--not too much or too little.  Researchers in other regions have found that tall fescue and orchardgrass grown in moderate shade yield better than those grown in heavy shade.  Neel has found that pasture plants do best in up to 25 percent tree shade in the frequently cloudy Appalachian Region.