Effects of Cover Crops in No-Tillage Crop Rotations in Eastern and Western Kansas.

Increasing popularity of conservation tillage has stimulated the need for more efficient no-till cropping systems. A study has been established to determine the impact of cover crops on no-till crop rotations in eastern and western Kansas in 2007 and 2008. Plots were established at Garden City and Manhattan in 2007. The Manhattan study consists of a three year, no-till cropping system of winter wheat-grain sorghum-soybean. Six cover crop treatments were incorporated into the fallow period following wheat harvest consisting of sorghum-sudangrass (Sorghum bicolor L.), two soybean (Glycine max) cultivars, winterpea (Pisum sativum), canola (Brassica napus L.), and a chemical fallow. Five nitrogen treatments (0, 40, 80, 120, and 160 lbs/acre) were placed within each cover crop and applied prior to grain sorghum planting. Soil nutrient testing was conducted and included organic matter, pH, bulk density, phosphorous, potassium, and nitrogen. Highest sorghum grain yields were achieved with the chemical fallow (142 bu/acre) and winterpea (145 bu/acre) treatments in 2008. The double crop soybean treatment produced the lowest yield (114 bu/acre). In 2008, grain sorghum flag leaf N and grain N were both highest in the chemical fallow treatments. Sorghum-sudangrass and double crop soybeans produced the lowest sorghum flag leaf N and grain N contents. Sorghum flag leaf N was significantly different within cover crop treatments at the 0 and 40 lbs N applied treatments. The 80, 120, and 160 lbs N applied treatments showed no significant difference. The sorghum-sudangrass produced the largest biomass in both years (6151 and 8278 lbs/a in 2007 and 2008, respectively). These results indicate sorghum-sudangrass and double crop soybeans tie up the most N in the aboveground biomass. The results also suggest the sorghum N requirement is met at the 120 and 160 lbs N applied causing yields to peak at these levels.