Long-Term Tillage and N Management for Corn, Wheat, and Double-Crop Soybean Grown in Rotation on a Claypan Soil.

Long-term effects of tillage and fertilizer options are not well documented for crops in rotation in the eastern Great Plains. Following a 22-yr tillage and N management study on grain sorghum and soybean in rotation, this study was re-designed in 2005 to determine the effect of tillage and N management on yields of corn, wheat, and double-crop soybean in rotation, producing three crops in two years. Tillage options were conventional (chisel [corn and wheat], disk, and field cultivate), reduced (disk and field cultivate), and no-tillage and N management options were no N and N applied as broadcast, surface-band (dribble), or subsurface-band (knife) for the corn and wheat crops. No-till corn yields ranged from 44 to 88% of yields with conventional tillage, with reduced tillage resulting in intermediate yields. Fertilizing with N, regardless of application method, usually doubled corn yields obtained with no N. Greater corn yield was often obtained with knife than with broadcast or dribble applications, averaging 10% increase. Wheat yield was greater with conventional tillage than no-till in two of six years. Similar to corn, wheat yield was generally doubled by adding fertilizer N. Knifed N application resulted in greater wheat yield than with broadcast or dribble applications in three of six years. Double-crop soybean yield was greater with no-till in one year, less with no-till in one year, and unaffected by tillage in four of six years. Double-crop soybean yield was unaffected by previous N fertilization applied to the corn and wheat crops except in 2006 and 2012 where greater soybean yield was obtained where there had been no N applied. For this typical crop rotation and claypan soil of the area, corn and wheat often respond to tillage and subsurface placement of N. However, double-crop soybean yield is little affected by tillage and previous N fertilization.