Influence of Tillage, Timing and Rate of Nitrogen Application On Corn.

Optimum rate and timing of nitrogen application can help to increase yields. The objective of this study was to evaluate the efficiency of nitrogen application on corn (Zea mays L.) planted under no-till, strip-till, and conventional tillage systems. The research project was initiated with planting wheat (Triticum aestivum L.) cover crop in the fall of 2006 at Clemson University, Edisto Research and Education Center near Blackville, SC. A commercially available soil electric conductivity (EC) measurement system (Veris Technologies 3100) was used to identify variations in soil texture across the fields prior to planting corn and create soil zone maps using Global Positioning and Geographical Information Systems. Corn was planted across four different soil zones (based on the EC map) and under three tillage systems (no-till, conventional, and strip-till), two methods of N application (all at planting and split application), and five N rates (0, 45, 90, 134, and 179 kg N ha^-1). Higher corn grain yields were obtained from conventional and no-till than strip-till in 2007. According to the quadratic regression for conventional tillage, the optimum N rate for corn would be 170 kg ha^-1.  As for no-till and strip till, grain yields increased with increasing N rates at the rate of 9.7 kg ha^-1 of grain yield per every 1 kg N ha^-1  applied to corn for both systems. In 2008, higher grain yields were received from strip-till than no-till and conventional tillage. With each 1 kg of N applied to corn under strip till we would expect 12.5 kg ha^-1 of grain yield. The quadratic plateaus for no-till and conventional tillage indicated that estimated optimum N rates for corn would be 156 and 164 kg ha^-1, respectively.