Response of Seed and Oil Yields and Phosphorus Agronomic Efficiency of Soybean to Simultaneous Placement of Nitrogen with Phosphorus under Drought Stress

In order to study yield, yield components and agronomic efficiency of phosphorus in soybean affected by simultaneous placement of nitrogen with phosphorus, an experiment was carried out under moisture stress conditions, at Agricultural Research Station of Bu Ali Sina University, Hamedan, Iran in 2017 in a factorial split plot based on randomized complete block design with three replications. The first factor of moisture stress which was placed in the main plots included three levels of irrigation after 60, 90 and 120 mm evaporation, and two factors of nitrogen (in two levels of placement and no placement) and phosphorus (in two levels of placement and no-application) were appointed to sub plots. The results showed that with nitrogen placement the number of pods per plant and the number of seeds per pod were increased by 8 and 16.21%, respectively. Nitrogen placement with phosphorus increased grain yield by 11.4% compared to non-placement of nitrogen with phosphorus and yielded 3855 kg/ha. Nitrogen placement at irrigation after 60, 90 and 120 mm evaporation increased phosphorus agronomic efficiency by 14.3, 27.6 and 35.4%, respectively. Oil yield was increased by placing nitrogen with phosphorus at irrigation after 60 mm evaporation, by 19.7%, compared to phosphorus alone treatment. In general, nitrogen placing with phosphorus at all irrigation levels increased grain and oil yields and reduced the negative effect of moisture stress on soybeans.