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 fertilizer management have an important impact on alfalfa production. This research aimed to explore the effects of water and phosphorus (P) fertilizer on hay yield, nutrient quality, water-use efficiency (WUE) and phosphorus-recovery efficiency (PRE) of each cut of alfalfa under drip irrigation and to determine the best water and P interaction model for high quality and yield of alfalfa. In this study, different irrigation levels, i.e., 5.25, 6.0, and 6.75 ML ha-1 (referred to as W1, W2, W3, respectively), and P fertilizer levels (0, 50, 100, and 150 kg P2O5 ha-1 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 and to calculate WUE and PRE. The hay yield of each cut of alfalfa increased first and then decreased with increased P fertilizer under the same irrigation amount, and there was no significant difference among different irrigation treatments with respect to the hay yield of alfalfa. The crude protein (CP) reached a maximum under the W2P2 treatment. WUE decreased gradually with an increasing irrigation amount under the same P application. The WUE of alfalfa increased first and then decreased with the increase of P application 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 under the same irrigation amount. Therefore, we conclude that moderate irrigation (6.0 ML ha-1) and P fertilizer (100 kg P2O5 ha-1) combined with application, the alfalfa has higher WUE and PRE, and can significantly promote the alfalfa hay yield and nutrient quality of each cut.