intercropping of sorghum and chickling pea in limited irrigation regimes

to evaluate the quantitative and qualitative of forage in intercropping of sorghum and chickling pea under limited irrigation systems, an experiment was conducted in research farm, college of agriculture, university of tehran, during 2009 and 2010. the treatments were arranged as split plots consisted of three levels of irrigation regimes including control (irrigation after 70mm evaporation from evaporation pan class a) (ir70), moderate limited irrigation (irrigation after 100mm evaporation from evaporation pan class a) (ir100) and sever limited irrigation (irrigation after 130mm evaporation from evaporation pan class a) (ir130) assigned to the main plots and eight sole and intercrop combinations of sorghum and cowpea including sole cropping of sorghum (weed free), sole cropping of sorghum (weed infested), sole cropping of cowpea (weed free), sole cropping of cowpea (weed infested), sorghum + 40% cowpea, 6. sorghum + 60% cowpea, sorghum + 80% cowpea and sorghum + 100% cowpea were assigned to the subplots. a complete randomized block design with three replications was used to analyze the data. as the water stress increased, the total forage yield followed a decreasing trend. the total forage yield decreased by 28% in sever limited irrigation (ir130) compared to control (ir70). the additive intercropping of sorghum and cowpea in all combinations over produced the sole cropping of each crop both in weed infested and weed free treatments. the highest total forage yield was produced in sorghum+60% cowpea treatment. the total forage yield in 2009 was higher than 2010. as the proportion of cowpea in additive intercropping with sorghum increased at normal (ir70) and moderate (ir100) limited irrigation systems, the total forage yield followed a decreasing trend while in severe limited (ir130) irrigation regime total forage yield increased. the highest crude protein content of 9.9 percent was achieved in sorghum+40% cowpea and sorghum+60% cowpea treatments. the highest soluble carbohydrates contents of 16.8% was achieved in moderate limited irrigation regime (ir100).