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 and disk for corn and wheat crops), reduced (disk only), and no-tillage and N management options were no N and N applied as broadcast, surface-band (dribble), and subsurface-band (knife) for the corn and wheat crops.  For two complete cropping cycles (2005-2008), all crops were affected by a tillage by year interaction.  No-till corn yields in 2005 were less than 50% of the yield in conventional or reduced tillage.  In 2007, corn grown in reduced-till and no-till yielded less than with conventional tillage.  In 2006, wheat yield was unaffected by tillage, but, in 2008, increasing tillage increased corn yield (conventional>reduced>no-till).  Though the relative difference was less than seen with corn and wheat, no-till reduced soybean yields in 2008 compared with tilled systems.  Knifing N produced the greatest corn and wheat yields.  However, differences in corn yield due to placement were greater in no-till than in tilled systems.  On a typical claypan soil of the area, crops often respond well to tillage and somewhat to subsurface placement of N.