Management Considerations for Mid-Southern Soybean Production.

Over the last decade, Mississippi’s cotton acreage has steadily declined with corn (Zea mays L.) and soybean (Glycine max Merr. L.) taking a significant proportion of the historical acreage.  On soils with a limited history of soybean in rotation, soybean nodulation may be absent or nodules may be limited in number. Low native populations of rhizobia result in reduced soybean yield due to inadequate nitrogen nutrition.  Recent estimates suggest that > 80%, or approximately 71.14 million bags of soybean seed planted in the U.S. are chemically treated (USDA-NASS, 2010). Two field experiments were established in both 2011 and 2012 to evaluate the influence of seed treatment fungicide and inoculant combinations on soybean yield and quality.  Experiments were established at the Delta Research and Extension Center in 2011 and 2012.  The remaining site was established in a grower field near Redwood, MS in 2011.  Cotton was the previous crop grown at all experimental locations, except one, were winter-wheat was previously cropped.  Each experiment was arranged as a randomized complete block with treatments defined by a 2 (inoculant) x 3 (fungicide) factorial arrangement plus an untreated control.  Soybean quality grade was unaffected by inoculant, fungicide, or their interaction.  Similarly soybean leaf and stem diseases were not influenced by any treatment combination.  Plant population was positively influenced by the main effect of fungicide, with ApronMaxx RFC producing significantly greater populations than ApronMaxx RTA and Trilex 6000 which were similar to the untreated control.  Soybean grain yield was influenced by the significant inoculant x fungicide interaction.  In general, fungicide seed treatments or the combination of fungicide and inoculants produced similar or greater grain yield than the untreated control when compared with inoculants alone. Further research is needed to evaluate new and upcoming inoculant and fungicide seed treatments and their compatibility.