Effect of Biological and Chemical Phosphorous Fertilizers on Grain Yield of Two Grain Sorghum (Sorghum bicolor L.) Cultivars under Deficit Irrigation Conditions

To assess the response of two grain sorghum cultivars; Kimiya and Speedeh to different phosphorous fertilizers under deficit irrigation conditions, a field experiment was conducted in Research Farm of College of Agriculture, University of Tehran in Karaj, Iran, in 2009 and 2010 growing seasons. The treatments were arranged as split-split plots in randomized complete block design with three replications. Irrigation regimes of normal weekly irrigation (control) (IRN) and deficit irrigation (IRS) were assigned to the main plots, and sorghum cultivars (Kimiya and Speedeh) to the sub plots and phosphorus fertilizers levels: P0 (no phosphorus fertilizer), chemical phosphorus fertilizer according to soil test (P100), biological phosphorus fertilizer of a mixture of micorrhiza fungi (Glomus intraradices) and phosphate solubilizing bacteria (Pseudomonas fluorescens) (M+Ps), and integrated application of P50+ M+Ps were assigned to sub-sub plots. Results showed that in normal irrigation regime grain yield of cv. Speedeh was 9508 kg/ha while in deficit irrigation regime it produced only 7192 kg/ha. This is while cv. Kimiya had 10368 and 8795 kg/ha of grain yield in normal and deficit irrigation regimes, respectively. Integrated phosphorus fertilizer application affected grain yield under normal and deficit irrigation conditions and proved to be a suitable substitute for P100. Results also indicated that grain sorghum cv. Kimia could be suggested as a suitable cultivar for grain production under deficit irrigation conditions with integrated phosphorous fertilizers application.