Abstract

Drought is the most important limiting factor for crop production; it is becoming an increasingly severe problem in many regions of the world. Sorghum is among the most important forages used in arid and semi-arid regions of southeastern Iran, but its growth and yield is often constrained by water deficit and poor productivity of sandy soil. Irrigation water is becoming scarcer and more costly. The addition of  water-saving superabsorbent polymer (SAP) in soil can improve soil physical properties, crop growth and yield and reduce the irriga­tion requirement of plants. This experiment was conducted on sorghum var ‘Speedfeed’ grass in Zahedan, Iran during 2009 and 2010 seasons. The experimental design was a split-plot with two factors including four irrigation regime (providing 40, 60, 80 and 100% from consumptive (ET crop) of sorghum) as main plots and four amounts of SAP (0, 75, 150 and 225 kg ha^-1) as subplots in a completely randomized block design with three replications. Irrigation level and SAP had significant effects on number of leaves per plant, number of tillers per plant, leaf area index, leaf area duration, relative water content and dry matter. The results indicate that irrigation to meet 80% of the water requirement with 75 kg ha^-1 SAP may provide a desirable dry matter.

Key words: Dry matter yield, forage sorghum, irrigation level, superabsorbent polymer.

Abbreviation

Abbreviations: DM, Dry matter yield; LAD, leaf area duration; LAI, leaf area index; NL, number of leaves per plant; NT, number of tillers per plant; RWC, relative water content; SAP, Superab A200 polymer.