Investigation of Crop Water Productivity and Yield in Different Systems of Tillage and Crop Residues

Currently, the area of agricultural land under  conservation practices in the world exceeds 180 million hectares, one of the main advantages of which is improvement in crop water productivity (CWP). An investigation in soybean cultivation  in a farm with different level of management of residues was carried out in a randomized complete block design with split plot design in 2010 and 2011 at Gorgan Agriculture Research Station. Main treatment was residue management at three levels: R1: burning of residue , R2: retaining 50% of residues, and R3: maintaining 100% of residues; the secondry treatment was tillage practises at three levels: T1: conventional tillage (plowing + disk + row crop planter), T2: minimum tillage (stubble cultivator + row crop planter) and T3: no tillage (sowing with no till planter). The best results obtained from R2 and T3: 42.7% and 17.4% increase in yield respectively, comparing R1 and T1. The highest and lowest of water consumption level were found  3950 m3 ha-1 and 2690 m3 ha-1 in  R1 and R3 respectively. The maximum and minimum CWP were found in R2 and R1 treatments with 1.13 kg m-3and 0.55 kg m-3 respectively. Sowing with no tillage system in irrigated conditions improved CWP by 15.3% compared to the conventional method.