施磷对川西北高寒草地土壤磷形态及有效性的影响

以川西北高寒草地为研究对象，采用随机区组设计，设置0、10、20、30、40、50、60 g/m²的过磷酸钙(P₂O₅,16%)施肥试验，分析土壤不同形态磷含量和有效磷(Olsen-P)含量变化特征，探究施磷对川西北高寒草地土壤磷形态及有效磷的影响。结果表明：(1)随施磷量增加，土壤总磷(TP)含量先增加后趋于平稳而Olsen-P含量减少。高水平(50、60 g/m²)施磷下氢氧化钠有机磷(NaOH-Po)及残留磷(Residual-P)是高寒草地主要的磷素累积形态，其含量显著高于不施磷处理；(2)树脂交换态磷(Resin-Pi)、碳酸氢钠无机磷(NaHCO₃-Pi)、碳酸氢钠有机磷(NaHCO₃-Po)和氢氧化钠无机磷(NaOH-Pi)含量随施磷量增加整体呈先增加后降低趋势，表层土壤30 g/m²磷肥用量下其值均为最高，分别为21.54、22.94、65.86、64.48 mg/kg。酸溶性无机磷(HCl-Pi)随施磷量增加整体呈下...

Effects of phosphorus fertilization on soil phosphorus fractions and availability in an alpine grassland of northwestern Sichuan

In order to reveal the effect of phosphorus fertilization on soil phosphorus fractions and availability in alpine grassland, 0, 10, 20, 30, 40, 50 and 60 g/m² of phosphorus (P₂O₅, 16%) fertilization gradients were set with random block design in northwestern Sichuan. The content of soil phosphorus fractions and available phosphorus (Olsen-P) were estimated. The results showed that: (1) Soil total phosphorus (TP) increased firstly and then varied slightly but Olsen-P decreased significantly with increasing phosphorus fertilization doses. NaOH-Po and Residual-P were the main fractions accumulated in 50 and 60 g/m² phosphorus fertilization treatments in alpine grassland, and their contents were significantly higher than that in non-fertilization treatment; (2) Soil Resin-Pi, NaHCO₃-Pi, NaHCO₃-Po and NaOH-Pi increased firstly and then decreased with increasing phosphorus fertilization doses, and they peaked at 21.54, 22.94, 65.86 and 64.48 mg/kg², respectively, under 30 g/m² phosphorus fertilization treatment in the topsoil. HCl-Pi decreased with phosphorus fertilization doses; (3) Random Forest regression and Path analysis showed that NaOH-Po and Residual-P were the sinks of Olsen-P transformation. NaOH-Po negatively correlated with soil pH and Residual-P positively correlated with Fe, Al content and microbial biomass phosphorus (MBP). Thus, when we applied phosphorus fertilization to alpine grassland, Olsen-P content could be enhanced by reducing NaOH-Po and Residual-P accumulation through regulating soil pH, Fe, Al content and MBP. The results are expected to provide clues for future fertilization management in alpine grassland of the northwestern Sichuan.