Abstract: To explore the effects of different phosphorus application rates on rhizosphere soil microenvironment and hay yield of alfalfa under drip irrigation. Four phosphorus (P₂O₅) gradients were set up：0(P₀),50(P₁),100(P₂) and 150 kg·hm^-2(P₃). Fertilization was applied with drip irrigation mode. The number of microorganisms,enzyme activity,soil physicochemical properties in alfalfa rhizosphere soil and hay yield were determined and analyzed comprehensively. The results showed that the number of fungi and actinomycetes and the activities of urease and catalase in rhizosphere soil of alfalfa reached the maximum under P₂ treatment,which were 6.04,6.15 lg cfu·g^-1 and 933.54,945.91 U·g^-1·d^-1,respectively. The number of bacteria reached the maximum value of 7.14 lg cfu·g^-1 under P₃ treatment;alkaline phosphatase activity reached the maximum at 14 939.80 U·g^-1·d^-1 under P₁ treatment. The total phosphorus and available phosphorus contents in rhizosphere soil gradually increased with the increase of phosphorus application rate,and reached the maximum value in P₃ treatment. However,the pH value and water content in rhizosphere soil without phosphorus application were significantly higher than those in other treatments (P<0.05). The hay yield of alfalfa reached the maximum in P₂ treatment,which was 21.82 t·hm^-2. Through a comprehensive evaluation,when the phosphorus application rate was 100 kg·hm^-2,it was beneficial to improve alfalfa rhizosphere soil microenvironment,thereby increasing alfalfa hay yield.

Key words: Alfalfa, Phosphorus application, Rhizosphere soil, Microenvironment, Hay yield

摘要： 为探究不同施磷量对滴灌紫花苜蓿根际土壤微环境及干草产量的影响，试验设置4个施磷(P₂O₅)梯度：0(P₀)，50(P₁)，100(P₂)和150 kg·hm^-2(P₃)，采用滴灌模式随水滴施，测定紫花苜蓿根际土壤微生物数量、酶活性、土壤理化性质及干草产量，并进行综合分析。结果表明，紫花苜蓿根际土壤真菌、放线菌数量及脲酶、过氧化氢酶活性在P₂处理下达到最大值，分别为6.04，6.15 lg cfu·g^-1及933.54，945.91 U·g^-1·d^-1；细菌数量在P₃处理达到最大值，为7.14 lg cfu·g^-1；碱性磷酸酶活性在P₁处理达到最大值，为14 939.80 U·g^-1·d^-1。根际土壤全磷及有效磷含量随着施磷量的增加呈逐渐增加的趋势，至P₃处理达到最大值，但根际土壤pH及含水率均为未施磷显著高于其他处理(P<0.05)。苜蓿干草产量在P₂处理达到最大值，为21.82 t·hm^-2。综合评定，适宜的施磷量(100 kg·hm^-2)有利于改善紫花苜蓿根际土壤微环境，进而提高苜蓿干草产量。

关键词: 苜蓿, 施磷量, 根际土壤, 微环境, 干草产量