Effects of Limited Irrigation Regime and Phosphorus Fertilizers on Quantitative and Qualitative Parameters of two Grain Sorghum Cultivars (Kimiya and Speedeh)

To evaluate the effects of biological phosphorous, chemical fertilizers and limited irrigation regime on quantitative and qualitative characteristics of two different grain sorghum cultivars (Kimiya and Speedeh), this experiment was conducted in research farm of College of Agriculture, University of Tehran during 2009 growing season. The experimental treatments were arranged as split split plot based on a randomized complete block design with three replications. The irrigation regimes viz: full irrigation (IRN) and limited irrigation (IRS) were assigned to the main plots and the grain sorghum varieties viz: Kimiya (KI) and Speedeh (SP) were assigned to the sub plots. Four phosphorous fertilizing systems viz: control, no phosphorous chemical fertilizer application and no biological fertilizer, (P0), complete phosphorous chemical fertilizer as triple super phosphate according to soil test (P100), seed inoculation by Pseudomonas bacteria and mycorrhiza fungi (M+Ps) and seed inoculation by Pseudomonas bacteria and mycorrhiza fungi + 50% of chemical phosphorous fertilizer(P50+M+Ps), were assigned to sub sub plots. The results indicated that in full irrigation system the highest biological yield was produced by integrated application of P50+M+Ps while at limited irrigation system the highest biological yield was achieved by both integrated fertilizer (P50+M+Ps) and biological fertilizer. The highest grain yield under full irrigation system was produced by complete chemical fertilizer (11694 kg/ha). However, under limited irrigation system, biological fertilizer (9479 kg/ha) and integrated fertilizer (9186 kg/ha) produced the highest grain yield. Across two studied varieties, kimiya variety produced almost 8 percent higher grain yield. The phosphorus content in Kimiya variety was higher than Speedeh.However, Speedeh produced more protein than Kimiya. The application of limited irrigation tend to decrease the phosphate content in Speedeh variety, while Kimiya showed no significant response to limited irrigation in this regard. The overall grain yield decreased by 17% in limited water application while water saving in the same treatment was 41% compared to complete irrigation. This result indicated the profitability of limited irrigation system in grain sorghum production in Iran.