Soybean irrigation scheduling by using the temperature difference of the air and canopy cover l

The crop water stress index depends on the temperature difference of the air and canopy cover. It is a reliable method to scheduling irrigation and plants water status.This study carried out to soybean irrigation scheduling using of the crop water stress index in Research Farm of Agricultural Faculty at Lorestan University.For this purpose, soybean was growing under irrigation levels I1 (100%), I2 (80%), I3 (60%) and I4 (40%). Base on the results, the average of CWSI was calculated during the growing season for treatments I1, I2, I3 and I4, respectively, 0.18, 0.37, 0.61 and 0.84; so that CWSI increased a rate of 0.15% per unit of irrigation water reduction. Also, the relationship between grain yield and CWSI showed a high correlation with r= 0.98 that is significant at the level of 5% and the yield decreased by increasing the amount of CWSI, so that highest and lowest of yield obtained in I1 and I4 equal to 1764.7 and 466.1 Kg/hec, respectively. According to the no stress treatment (I1), CWSI=0.18 was used to determine of irrigation timing. Finally, the relationship needed to determine irrigation times for soybean in the total of growth period was estimated:.