THE PRODUCTIVITY OF INTERCROPPING SOME SOYBEAN VARIETIES WITH CORN UNDER LOW LEVELS OF IRRIGATION WATER

Yield of intercropped soybean when grown under water deficiency is depended on the choice of the suitable cropping system and soybean varieties. Three experiments were conducted at Giza Agricultural Experiments and Research Station, Faculty of Agriculture, Cairo University, (Egypt) during the three successive seasons 2018, 2019 and 2020. The objective of this study was to evaluate the effect of water deficiency on different cropping systems and some soybean varieties. Forty eight treatments were the combinations among three levels of applied irrigation water (7140, 5712 and 4284 m3/ha were expressed as 100 "WL0", 80 "WL1" and 60%"WL2", respectively), cropping systems (alternating ridges 2:2 "Int1", mixed "Int2" and solid plantings of corn "ridges Sc1 and beds Sc2" and soybean "ridges Ss1 and beds Ss2") and four soybean varieties Giza 21, Giza 22, Giza 35 and Giza 111. The experimental design was split-split plot distributions in randomized complete blocks design with three replications. The results indicated that corn grain yields of WL0 and WL1 were not significantly different from each other, meanwhile the same trend was achieved for soybean seed yield in all seasons. Generally, mixed intercropping system (Int2) gave higher corn grain and soybean seed yields per ha than alternating ridges (Int1) without significant differences with solid plantings in all seasons. Corn grain and soybean seed yields per ha were affected significantly by (the interaction between W x CS x V in all seasons); whereas statistically significant effects of W x CS x V for corn grain and soybean seed yields per ha in the first and second seasons.Int2 recorded higher irrigation water use efficiency (IWUE) and land equivalent ratio (LER) than Int1 and solid plantings in all seasons, especially under low levels of irrigation water. Growing soybean variety Giza 21 with corn in raised beds 140 cm width under 5712 m3/ha of irrigation water should be recommended.