Effect of Light Radiation Absorption and Its Use Efficiency in Intercropping of Soybean and Millet Under Water Deficit Stress

To study the effect of water deficit stress on leaf area, radiation use efficiency and dry matter production of soybean and millet in intercropping, a split plot experiment based on randomized complete block design with three replications was carried out, in 2015 at the Research Station of Agricultural Faculty of Bu-Ali Sina University. The main factor consisted of three levels of water deficit stresses (irrigation after 60, 90 and 120 mm evaporation from pan) and sub factor of five replacement intercropping treatments sol cropping of soybean (100S), sol cropping of millet (100M), 67 % S 33 % M (67S:33M), 50 % S 50 % M (50S:50M) and 33 % S 67 % M (33S:67M). The results showed that the highest leaf area index of soybean and millet in sol cropping were 5.68 and 3.23 respectively. Severe water deficit stress significantly decreased leaf area index of soybean and millet by about 30.03 and 30.33 percent, respectively, as compared to well-watered condition. The highest dry matter (613 and 540 g.m-2) belonged to sol cropping of soybean and millet, respectively. Severe water deficit stress reduced dry matter of soybean and millet by 39.87 and 31.556 percent respectively as compared to the control. Radiation use efficiency of millet in (33S:67M), (50S:50M) and (67S:33M) intercropping ratios were 24.85, 29.86 and 26.76 percent more than sol cropping of millet, respectively. Radiation use efficiency of soybean reduced in the intercropping. Mean radiation use efficiency of soybean in growing season ranged from 0.97 g.mj-1 in the (33S:67M) ratio to 1.77 g.mj-1 in the sol cropping of soybean. The results showed a negative effect of water deficit stress on radiation use efficiency of both millet and soybean.