Effect of Kochia (Kochia indica) Plant Density on Yield and Some Physiological Characteristics of Sorghum under Salinity Stress

This study was carried out in two years, 2012 and 2013, to determine the effects of salinity and different kochia plant densities on yield and some physiological characteristics of sorghum (cv. Sepideh) at Salinity Research Center, National Salinity Research Center, Yazd, Iran. Treatments consisted of water salinity levels: 2 (control), 6, 10, and 14 dS m-1 of NaCl as main plots and different kochia (K. indica) densities: 0 (weed free sorghum, D0), 80 (D1), 60 (D2), and 40 (D3) cm between kochia plants on the sorghum row as sub plots. Results showed that at each salinity level, increase in kochia plant density was accompanied by reduction in sorghum dry matter, leaf area index and crop growth rate. Decreases in dry matter and leaf area index of sorghum due to kochia were more pronounced when grown at salinities of up to 6 dS m-1. Chlorophyll content index at 6, 10 and 14 dS m-1 were 23, 32 and 40% lower than the non-saline control. Increase in irrigation water salinity was accompanied by increase in canopy temperature. Canopy temperature of plants subjected to 14 dS m-1 of salt was higher than the non–stressed control by 13.6%. The weed free sorghum treatment had the highest canopy temperature. Therefore, it is necessary to control both salinity and Kochia indica to avoid meaningful decreases in sorghum yield.