Phosphorus Utilization Efficiency and Yield Responses of Drip Irrigated Cotton under Plastic Film Mulching to Three Types of Water Soluble Phosphorus Fertilizers

Objective] To select suitable phosphate fertilizer types for drip irrigated cotton under plastic film mulching in calcareous soil, the lint yield responses and phosphorus (P) utilization rate of cotton to three types of water soluble P fertilizer were compared. Method] Two-year field trials were conducted with four treatments including no P fertilizer (P0), monoammonium phosphate (MAP), diammonium phosphate (DAP) and triple superphosphate (TSP). All P fertilizers and potassium fertilizer as potassium chloride were applied as base fertilizer before sowing. To maintain nutrient balance, additional nitrogen was applied as urea. Ten percent of nitrogen was applied as base fertilizer before seeding, and 90% of nitrogen was applied with drip irrigation. The cotton dry matter, lint yield, P uptake and soil available P were measured at harvest. Result] When compared with the no P fertilizer control, the lint yields of MAP, DAP and TSP increased by 11.01%, 6.97% and 8.52%, respectively, and shoot dry matter increased by 10.96%, 4.86% and 8.36%, respectively. MAP significantly increased the shoot dry matter and lint yield of cotton when compared with DAP but not TSP. Application of the three P fertilizers significantly increased P uptake of cotton, and average utilization rates of MAP, DAP and TSP were 26%, 22% and 24%, respectively. Input of P fertilizers improved economic benefit. The profit from MAP use was higher than that of DAP and TSP. However, the effects of MAP, DAP and TSP on soil available P were not significant. Conclusion] Application of MAP, DAP and TSP could significantly increase cotton yieldand economic benefit, with the effect of P fertilizers in the order of MAP > TSP > DAP.