Nitrogen Management in No-Tillage and Ridge-Tillage Systems Affects Short-Season Corn Grown on Claypan Soil

Success of conservation tillage systems requires good fertilizer management, especially nitrogen applied to crops grown on claypan soils in the eastern Great Plains. Recently introduced, short-season corn (Zea mays L.) hybrids, that mature earlier and potentially avoid drought problems common on these soils in late summer, provide producers with another viable cropping option. However, information on N management in conservation tillage systems is lacking for short-season corn grown on claypan soils. The objective of this study was to examine the effect of fertilizer N at rates of 0, 30, 60, 90, and 120 lb/acre applied by surface broadcast, surface band (dribble), and subsurface band (knife) placement methods on short-season corn grown in no-tillage and ridge-tillage systems. Average corn yield in 1997 was about 25 bu/acre more with ridge tillage than with no tillage when fertilizer N was applied at any rate. However, this trend was not apparent in 1996 and 1998, when yields were lower because of less rainfall. In 1996 and 1998, yield was not increased at N rates greater than 60 lb/acre, but in 1997, maximum yield was obtained at the 120 lb/acre N rate. Nitrogen placement effects on yield were inconsistent. Yield improvements resulting from increased N rate can be attributed to improved yield components, especially the number of kernels per ear, which was doubled with N at 120 lb/acre compared to no fertilizer N. Increasing N rate resulted in small increases in crude protein concentration in the corn grain. Even though more samples were contaminated with aflatoxin and at higher levels in the drier years, tillage and N management had little effect on aflatoxin concentrations. Corn grown on a claypan soil can respond to increased N rate and conservation tillage systems, especially in higher rainfall years, but the effect due to N placement is inconsistent.