Effect of polymer and irrigation regimes on dry matter yield and several physiological traits of forage sorghum

Drought stress is one of the most serious problems in crops production in the arid and semi-arid regions. Application of some materials such as superab A200 polymers (SAP) in soil can improve soil water reservation. They can also decrease water losses, fertilizer leaching in soils, effects of water deficiency in plants and so can improve the yield in the arid and semi-arid regions. This experiment was conducted on forage sorghum (Sorghum bicolor (L.) variety 'Speedfeed') in Zahedan, Iran during 2010 season. The experimental design was a split-plot with two factors including four irrigation regimes (providing 40, 60, 80 and 100% of the water requirement of sorghum calculated from pan evaporation) as main plots and four amounts of SAP (0, 75, 150 and 225 kg ha super(-1)) as subplots in a completely randomized block design with three replications. Irrigation level and SAP had significant effects on chlorophyll index, leaf area index, leaf area duration, crop growth rate, relative water content and dry matter. The results indicate that irrigation to meet 80% of the water requirement with 75 kg ha-1 SAP which may provide a desirable dry matter.