Mycorrhizae play an important role in driving soil phosphorus (P) transformation, while intercropping or phosphate application influences rhizosphere mycorrhizal traits and enzyme activity. However, the mycorrhizal-mediated mechanism through which intercropping promotes P activation in red soil remains poorly understood. Based on a 7-year field experiment, we analyzed the effects of maize//soybean intercropping on maize yield, soil P fractions, mycorrhizal colonization, and the rhizosphere alkaline phosphatase activity (APA) with two plantation models, maize monoculture and maize//soybean intercropping under four phosphate application rates (0, 26.2, 39.3, and 52.4 kg P·hm-2). We further explored the mycorrhizal-mediated role of intercropping on promoting phosphorus activation. The results showed that maize//soybean intercropping significantly increased maize yield, the proportion and content of liable P pools, P activation, and mycorrhizal colonization. Under the four different P application levels, intercropping increased maize yield by 21.1%, 60.0%, 58.5%, and 44.3%, respectively. The proportion of liable phosphorus pools under intercropping increased significantly by 27.3%, 18.2%, 10.6%, and 9.2%, respectively. The Resin-P content increased by 13.7%, 31.3%, 22.9% and 18.4%. NaHCO3-Pi content increased by 15.9%, 28.8%, 16.1% and 6.9%. NaHCO3-Po content increased by 23.8%, 19.5%, 11.8% and 2.6%. The P activation coefficient (PAC) increased by 36.7%, 51.4%, 19.8% and 14.1%. Intercropping increased the colonization rate by 35.2%, 42.9%, 28.8% and 25.9%, hyphal density by 21.7%, 67.5%, 27.5% and 6.0%, spore density by 30.8%, 35.7%, 28.2% and 21.9%, total glomalin by 8.3%, 30.2%, 25.1%, and 17.3%, and rhizosphere APA by 20.6%, 24.6%, 16.8%, and 13.8%, respectively. Random forest analysis indicated that the liable phosphorus pools, Resin-P, NaHCO3-Po, NaHCO3-Pi, were the most important factors driving soil P activation. Key factors influencing P fractions, in descending order of importance, were total glomalin, alkaline phosphatase, hyphal density, mycorrhizal colonization rate, and spore density. Structural equation modeling further demonstrated that maize//soybean intercropping promoted P activation primarily by enhancing mycorrhizal colonization and rhizosphere alkaline phosphatase activity, which in turn increased the content and proportion of both liable organic and inorganic phosphorus.
菌根在介导土壤磷转化过程中发挥重要作用,间作和施磷影响菌根和根际酶活性,但间作下红壤磷活化的菌根介导作用尚不明确。本研究基于连续7年的红壤田间定位试验,设置玉米单作和玉米//大豆间作2种种植模式,在4个施磷水平(0、26.2、39.3、52.4 kg P·hm-2)下,分析玉米//大豆间作对玉米产量、红壤磷组分、菌根特征、根际碱性磷酸酶活性的影响,探究间作促进红壤磷活化的菌根介导作用。结果表明: 玉米//大豆间作显著提高了玉米产量、红壤活性磷库比例和含量,促进了红壤磷活化和菌根定殖。在4个施磷水平下,与对应单作相比,间作玉米产量分别提高了21.1%、60.0%、58.5%和44.3%,土壤活性磷库占比分别显著提高了27.3%、18.2%、10.6%和9.2%,其中树脂膜浸提态磷(Resin-P)含量分别增加13.7%、31.3%、22.9%和18.4%,碳酸氢钠提取态无机磷(NaHCO3-Pi)含量分别增加15.9%、28.8%、16.1%和6.9%,碳酸氢钠提取态有机磷(NaHCO3-Po)含量分别增加23.8%、19.5%、11.8%和2.6%,红壤磷活化系数(PAC)分别提高36.7%、51.4%、19.8%和14.1%。间作玉米菌根侵染率分别提高35.2%、42.9%、28.8%和25.9%,菌丝密度分别提高21.7%、67.5%、27.5%和6.0%,孢子密度分别提高30.8%、35.7%、28.2%和21.9%,总球囊酶素分别提高8.3%、30.2%、25.1%和17.3%,碱性磷酸酶活性分别提高20.6%、24.6%、16.8%和13.8%。随机森林模型分析表明,对红壤磷活化贡献最大的为活性磷库(Resin-P、NaHCO3-Po、NaHCO3-Pi),而影响红壤活性磷组分的重要贡献因子依次为总球囊酶素、碱性磷酸酶活性、菌丝密度、菌根侵染率、孢子密度。结构方程模型进一步揭示,玉米//大豆间作通过提高菌根定殖与根际碱性磷酸酶活性,提高了红壤活性磷含量和比例,从而促进了红壤磷活化。.
Keywords: alkaline phosphatase activity; intercropping; mycorrhizal characteristic; phosphate application level; phosphorus fraction.