| چکیده انگلیسی مقاله |
In order to evaluate 26 crop rotation systems, this study was conducted in Research Field of Ramin Agricultural and Natural Resources University in 1999-2003 cropping seasons. Wheat, alfalfa, maize, and canola as main crops and broad-bean, sesame, sudangrass, clover, silage maize and common bean as second crops were planted within traditionally practised crop rotation systems. Studied crops were grouped in 26 different rotation systems using randomized complete blocks design (RCBD) with four replications. Results showed as compared to continuous wheat (5103 kg.ha-1), wheat grain yield followed alfalfa and canola increased by 24% and 17%, respectively. However, wheat grain yield followed fallow, maize, sudangrass, silage maize and sesame decreased by 1, 1, 16, 20, 22%, respectively. In comparison of 9 of four-years rotation systems with one period fallow showed that wheat grain yield decreased as the proportion of cereals in crop sequences increased and the proportion of legume crops decreased. Replacement of maize with sudangrass in three-years rotation system decreased wheat grain yield by 22%. Canola was the best previous crop for wheat crop in three-years rotation system as in this ystem wheat grain yield increased by 33% when compared to sesame. Broad-bean and clover as previous crop for maize, when compared to wheat-maize rotation systems, increased maize grain yield by 19 and 22%, respectively. Comparison of different rotation systems showed that the highest maize grain yield was obtained in fallow-broad bean-maize (12020 kg.ha-1) in three years crop rotation system, wheat-maize-clover-maize (11290 kg.ha-1) in four years crop rotation system, wheat-wheat-maize-clover-maize (11450 kg.ha-1) in five years crop roation system and fallow-wheat-wheat-maize-clover-maize (11810 kg.ha-1) in six years crop rotation system. |