Yield, nutrient quality and water and phosphorus recovery efficiencies of alfalfa under different drip irrigation and phosphorus levels in Northern Xinjiang, China

Rational water and fertiliser management have an important impact on alfalfa production. This research aimed to explore the effects of water and phosphorus (P) fertiliser on water‐use efficiency (WUE) and phosphorus‐recovery efficiency (PRE) of each cut of alfalfa under drip irrigation and to determine the optimal interaction ratio of water and phosphorus to improve the quality and yield of alfalfa. Different irrigation levels were set, i.e., 5250, 6000 and 6750 m3/ha (referred to as W1, W2, W3, respectively), and P fertiliser levels (0, 50, 100 and 150 kg/ha P2O5 referred to as P0, P1, P2, P3, respectively) were set to determine the hay yield and nutrient quality of each cut of alfalfa under drip irrigation. The hay yield of each cut of alfalfa increased first and then decreased with increased P fertiliser under the same irrigation amount. WUE decreased gradually with an increasing amount of irrigation under the same P application rate. The WUE of alfalfa increased first and then decreased with the increase of P application rate under the same irrigation amount, and WUE was 0.20%–4.75% (2016) and 1.31%–6.22% (2017) higher in the P treatments than in the non‐phosphorus treatments. PRE decreased gradually with increasing P application rate under the same irrigation amount. Therefore, we concluded that moderate irrigation (6000 m3/ha) and P fertiliser (100 kg/ha) optimised WUE, PRE, hay yield and nutrient quality.