High input management practices' influence upon soybean growth, mineral nutrition, and pathogen defense

Ryan S Henry, Purdue University

Abstract

Soybean growers have begun to incorporate fungicides and insecticides into their management programs with the goal of inducing physiological changes and enhancing production. Yield increases have been reported in wheat and barley, but the yield response to these pesticides has generally been inconsistent in soybean. Field experiments were established in 2009 and 2010 at three sites in Indiana. Soybean was treated with a strobilurin fungicide, pyraclostrobin, and insecticide, lambda-cyhalothrin, and the yield and yield components were measured. Yield was increased by 100 kg ha-1 and 150 kg ha -1 by a R4 application of pyraclostrobin alone and by lambda-cyhalothrin alone, respectively. Seed mass was increased 3% by pyraclostrobin, while seed number m-2 was increased 5% by lambda-cyhalothrin. No other yield component was influenced by the fungicide or insecticide. One commonly reported consequence of these fungicides is prolonged chlorophyll retention, possibly due to lower ethylene levels. Because ethylene is known to be important for pathogen defense, any alteration in its production or quantity may have an effect on disease development. Soybean treated with pyraclostrobin decreased the ethylene precursor molecule ACC in leaves. Likewise, growth of the bacterial pathogen Pseudomonas syringae pv. glycinea was attenuated in pyraclostrobin-treated soybean, but growth of the necrotrophic fungus Botrytis cinerea was unaffected. Our results suggest that ethylene is influenced by this fungicide, but its effect on soybean pathogen defense response is dependent upon the pathogen. The recent release of a new genetic event of GR soybean, Roundup Ready2, provides growers with an additional tool to increase yields. Previous research has shown that glyphosate can reduce the macro and micronutrient content of non-glyphosate-resistant and first generation Roundup Ready soybean, possibly by complexation of the herbicide molecule with the nutrient. The objective of this experiment was to identify the effect of glyphosate on the concentration of macro and micronutrient in first and second generation GR soybean when grown using standard agronomic practices in Indiana. Our results indicate that while differences in accumulation of macro and micronutrients exist between the two cultivars tested, there was no effect due to glyphosate treatment.

Degree

M.S.

Advisors

Johnson, Purdue University.

Subject Area

Agronomy

COinS