Studying the dry matter yield and water use efficiency of forage sorghum under water deficit and applying superabsorbent polymer

In order to investigate the possibility of decreasing forage sorghum (Sorghum bicolor L. var speedfeed) water requirements applying of superabsorbent (SAP), without decreasing the dry matter yield and increasing the water use efficiency, and also to investigate the economic efficiency of applying superabsorbent (SAP), this experiment was conducted in Dashtak region of Zahedan during 2013 and 2014 seasons in a split-split plot with four irrigation regimes, providing 40, 60, 80 and 100% of the water requirements of sorghum, calculated from pan evaporation as main plots, four amounts of SAP )0, 75, 150 and 225 kg ha-1( as subplots and cutting as sub-subplots based on a completely randomized block design with three replications. The results indicated that the effect of irrigation regimes, SAP levels and their interaction effects of the two factors on dry matter yield, water use efficiency, and economic efficiency were significant. The regression models estimated showed that applying SAP in 100% ETc treatment had no effect on this trait but in the other irrigation treatments caused an increased the dry matter yield and water use efficiency. Therefore, applying 75 kg SAP per hectare along with 20% decrease in the sorghum’s water requirement in arid regions, the dry matter yield and water use efficiency is maintained similar to 100% sorghum’s water requirement. Also the greatest economic efficiency of applying SAP was secured at 75 kg SAP per hectare SAP level and 80% of sorghum’s water requirement.