The effects of crop residue management and tillage on soil fertility in corn-wheat rotation

A 4-yr field experiment (1999-2002) was conducted on a silty clay loam soil at laklak Research field of Hamedan to determine the effects of crop residue management and plowing depth on soil fertility and wheat yield in a maize-wheat rotation. In this investigation, four corn residue managements consisting of 1) Stalk shredding by maize stalk shredder 2)Stalk shredding by disk 3)Stalk shredding by rotivator 4) Removal of corn residue and two levels of plowing depth (20 and 30cm), were used. Corn residue management and plowing depths were combined in eight treatments. A factorial experiment based on randomized complete block design with three replications was used. Wheat residue were incorporated in soil by plowing to a depth of 20-25 cm in all plots. To evaluate the efficiency of shredding implements, percentage of chopped stalks were measured. To study the C organic changes, this index was measured in three stages (1- 13 April 1999, 2- 17 August 2000 and 3- 12 July 2002). Wheat yield and yield parameters, spike/m2, number of grain per spike and kernel weight, and corn grain yield were determined. Machine type had significant effect on precentage of chopped stalks. Maize stalk shredder had higher shredding content than the other two machines (disk and rotivator). Also after four years, incorporation of corn – wheat residue increased C and#1634and#1637organic about 25% and incorporation of wheat residue and removal of corn residue increased C organic about 16%. Wheat yield and corn grain yield were un affected by residue management or plowing depth, but wheat yield in 2002 increased about 40% compared with 1999. For economic evaluation of corn residue management and plowing depth. Partial budgeting was used. However , the residue management and plowing depth had no significant effect on wheat yeild. So the machines with low cost of operation is the best condition. Result showed that stalk shredding by disk has cost about 59. 6% and 59.7% lower than stalk shreder and rotivator, respectively.