Effects of pre-sowing irrigation and phosphorus application on water use and yield of spring wheat under semi-arid conditions

The effects of pre-sowing irrigation and phosphorus application on water use and grain yield of spring wheat were examined in a dry year on the semi-arid Loess Plateau of China. The study included four treatments: (1) with 30 mm pre-sowing irrigation but without application of phosphorus (W); (2) with phosphorus application but without pre-sowing irrigation (P); (3) pre-sowing irrigation (30 mm) plus phosphorus application (WP); and (4) without pre-sowing irrigation and phosphorus application (CK). The pre-sowing irrigation resulted in stronger seedlings and larger and deeper root systems, compared with the non-irrigated treatments. The root/shoot ratio in the irrigated treatments was significantly higher than in the non-irrigated treatments. Grain yields in P, W and WP were 1191.1, 2516.5 and 2734.1 kg ha−1, respectively, which were 30, 174 and 198% higher than that (917.7 kg ha−1) of CK, and at the same time grain yields in W and WP were also significantly higher than in P. Water use efficiencies in terms of grain yield were 1.27 and 1.45 kg m−3 in W and WP, respectively, being 119 and 150% higher than that (0.58 kg m−3) of CK. The highest water use efficiency and grain yield consistently occurred in WP, suggesting that combination of pre-sowing irrigation and phosphorus application had a beneficial effect on improving water use and grain yield of spring wheat.