Effects of phosphatic fertilizer addition on plant community characteristics in an alpine grassland around Qinghai Lake

To determine the suitable amount of phosphate fertilizer to be used in an alpine grassland in the area surrounding Qinghai Lake, experiments were conducted in the mildly degraded alpine grassland of Xihai Town, Haiyan County in 2017. Treatments included 0 (CK), 120 (P₁), 240 (P₂), 360 (P₃), and 480 kg·ha^–1(P₄). The goal of the research was to examine the change in grassland plant community characteristics, to determine the optimal scheme for regional fertilization. The results showed that the application of diammonium phosphate significantly increased the important values for grasses, sedges, and legumes in grassland communities (P < 0.05). In particular, the coverage and importance value of lentils (Melilotoides archiducis-nicolai) (P < 0.01). The biomass of the grassland community increased significantly under different fertilization gradients(P < 0.05). The biomass of grassland community was higher, which was 31.28%～47.13% higher than that of the control, When the application rate of diammonium phosphate was 120～240 kg·ha^–1. The net income increased by 28.42%～38.37% compared with the control. The economically feasible amount of DAP was 120～240 kg·ha^–1 in the alpine grassland around Qinghai Lake.