Wednesday, November 15, 2006

Corn, Soybean, and Wheat Yields During Transition to Organic Cropping Systems.

Lawrence Grabau and Laura Harris. University of Kentucky, 1405 Veterans Dr., N122Q Ag Science North, Lexington, KY 40506-0312, United States of America

While organic vegetable production is well established in the US and elsewhere, organic grain crop production has proven more difficult to manage.  Perennial weed species [e.g., Johnson grass [Sorghum halepense (L.) Pers.], wild garlic [Allium ursinum L.], fungal diseases [Fusarium spp.], and insect outbreaks [true armyworms, Pseudaletia unipuncta]} may be manageable by organic methods in small areas of high value vegetable crops, but may prove much more complex to manage organically in large areas of modest margin grain crops.  Our objective was to compare the yields of corn [Zea mays (L.)], soybean [Glycine max (L.) Merrill], and wheat [Triticum aestivum L.] in three organic cropping systems.  For this presentation, we will focus on grain crop yields in transition from a conventionally managed alfalfa [Medicago sativa L.] system.  Each tested organic cropping system was managed as a two-year rotation with decreasing grain crop intensity as follows:  1) corn followed by 19 months of orchard grass [Dactylis glomerata L.]/red clover [Trifolium pratense L.] mix (one grain crop each two years), 2) corn, winter rye [Secale cereale L.] cover crop, soybean, and hairy vetch [Vicia villosa L.] cover crop (two grain crops each two years), and 3) corn, winter wheat, and double crop soybean (three grain crops each two years).  Further, we started each rotation in both its first year and its second year (in order to evaluate year effects), and included two locations [a Maury silt loam (fine, mixed, semiactive, mesic Typic Paleudalfs) near Lexington, KY and a Crider silt loam (fine-silty, mixed, active, mesic Typic Paleudalfs) near Princeton, KY].  Yields will be reported from all three organic grain cropping systems for 2005 (Lexington only) and 2006 (both locations).