Long-term yield response of corn, wheat, and double-crop soybean to tillage and N placement

On claypan soils of the eastern Great Plains, yield of no-till crops often lags yield of crops grown with tillage, especially cereals requiring sound N management. The objective of this 14-yr study was to determine the yield response of corn (Zea mays L.), winter wheat (Triticum aestivum L.), and double-crop soybean [Glycine max (L.) Merr.] in a 2-yr rotation to tillage system and N fertilizer placement. Tillage, N placement, or their interaction affected corn yield in all seven-corn crop-years. Corn yields averaged about 25% lower with no-till than with conventional or reduced tillage and were never greater with no-till in any year. Nitrogen fertilization increased corn yield by increasing kernels per ear; however, corn yield increase to subsurface band (knife) N applications compared with surface (broadcast or dribble) applications was only about 10%. In the lower-yielding no-till system, corn yield increase to knifed N fertilization was greater than in tilled systems and may partially ameliorate the no-till yield decline. Average wheat yield was unaffected by tillage. Adding N more than doubled wheat yield, but differences in wheat yield between preplant N placements methods were small. Average double-crop soybean yield was unaffected by tillage with few, inconsistent differences by year. Compared with no-till, tillage tended to increase soil P and K, but soil organic matter was just redistributed with no net increase with no-till. Thus, tillage and N placement treatments may affect corn but have lesser effects on wheat and double-crop soybean and soil properties in this rotation.