Short-term responses of soil and wheat yield to tillage, corn residue management and nitrogen fertilization

Corn residues management is a major problem in the southern part of Iran where irrigated wheat–corn–wheat rotation is a common practice. A two-year (2008–2010) field experiment was conducted as a factorial split plot design with three replications at the Agricultural Research Centre, College of Agriculture, Shiraz University, Shiraz, Iran to determine the influences of different amounts of corn (Zea mays L.) residues (0, 25 and 50%) incorporation and nitrogen (N) rates (75 and 150 kg ha−1) on some soil properties, yield and yield components of winter wheat (Triticum aestivum L.) under two tillage systems. Tillage treatments were moldboard plow followed by two harrow diskings and chisel plow tillage followed by a single harrow disking. The soil with chisel treatment had about 8 and 15% more soil organic carbon (SOC) and total N than moldboard plow treatment, respectively. Incorporation of increased amounts of corn residues and a higher N rate reduced C:N ratios in the chisel treatment in both years. Soil electrical conductivity (EC) increased with chisel plow and increasing amounts of residues incorporation and N rates. The lowest pH found in plots with no residue incorporation was 8.1 compared to 8.2 in plots with 50% residue incorporation. For treatments receiving 150 kg N ha−1, soil pH was significantly higher compared to treatments receiving 75 kg N ha−1. The highest wheat grain yields (about 8.5 t ha−1) were obtained with chisel treatment, 25–50% corn residue incorporation and application of 150 kg N ha−1. Incorporation of 25–50% of corn residues (7500–15,000 kg ha−1) is recommended to increase SOC in a wheat–corn–wheat rotation in this region.