适宜施氮量对粗齿冷水花根际微域土壤磷组分及磷酸酶活性的影响

  【目的】  适宜施氮可提高磷富集植物对磷过剩土壤的修复效率，研究适宜施氮处理下磷富集植物根际微域土壤磷组分的变化，可为利用磷富集植物提取土壤中过剩的磷提供理论依据。  【方法】  采用多隔层根箱土培试验，以磷富集植物矿山生态型粗齿冷水花为材料，非矿山生态型为对照，设磷处理的P质量浓度为800 mg/kg，氮处理的N质量浓度为0 (CK)和140 mg/kg，分析对比了两种生态型粗齿冷水花磷富集能力及根际微域土壤磷组分与磷酸酶活性的变化。  【结果】  1)适宜施氮量下，两种生态型粗齿冷水花地上部、地下部生物量和磷积累量均显著升高；矿山生态型地上部生物量和磷积累量分别为非矿山生态型的1.28和1.45倍。2)适宜施氮量下，两种生态型根际土壤中H₂O-P和NaHCO₃-Pi含量均增加；土壤H₂O-P和NaHCO₃-Pi含量均在距矿山生态型根际4 mm微域内显著高于非根际土壤，分别在距非矿山生态型根际4和2 mm微域内显著高于非根际土壤；土壤NaHCO₃-Po和NaOH-Pi、NaOH-Po含量在距两种生态型根际6 mm微域内显著低于非根际土壤；土壤HCl-Pi和HCl-Po和Residual-P含量在根际微域和非根际土壤之间无显著变化。不施氮和适宜施氮量下矿山生态型根际微域NaHCO₃-Pi含量均显著低于非矿山生态型，矿山生态型对土壤NaHCO₃-Pi的吸收利用能力更强。3)适宜施氮量下，两种生态型粗齿冷水花根际土壤磷酸酶活性均较对照增加，土壤酸性磷酸酶、碱性磷酸酶活性分别在距根际4和2 mm微域内显著高于非根际土壤，植酸酶活性在距根际8 mm微域内显著高于非根际土壤。不施氮和适宜施氮量下，矿山生态型根际微域土壤磷酸酶活性更高。  【结论】  高磷条件下，适宜施氮量 (140 mg/kg)增加了两种生态型粗齿冷水花根际微域土壤磷酸酶活性，且矿山生态型根际土壤磷酸酶活性更高，有利于根际微域土壤中磷由低有效态组分向高有效态组分转化，从而促进了植株的生长和磷素积累。

Effects of suitable nitrogen application on soil phosphorus fractions and phosphatase activities in rhizosphere microdomain of Pilea sinofasciata

  【Objectives】  Suitable nitrogen (N) application can improve the remediation efficiency of phosphorus (P) accumulating plants in soil with excess P. Clarifying the changes of P fractions in the rhizosphere microdomain of P-accumulating plants under suitable N application is beneficial for extracting excess P from soil.  【Methods】  A multi-compartment root box experiment was carried out. And mining ecotype (ME) of Pilea sinofasciata was used as the tested materials, with the non-mining ecotype (NME) being the control. P treatment concentration was 800 mg/kg and N treatment concentration was 0 (CK) and 140 mg/kg. The differences of P accumulation, soil P fractions and phosphatase activities were compared between the two ecotypes of Pilea sinofasciata.  【Results】  1) The biomass and P accumulation of the two ecotypes significantly increased under suitable N application condition, the shoot biomass and P accumulation of the ME were 1.28 times and 1.45 times than that of the NME, respectively. 2) With suitable N application, the concentration of H₂O-P and NaHCO₃-Pi increased in rhizosphere soil of the two ecotypes. The concentration of H₂O-P and NaHCO₃-Pi were significantly higher in the range of 4 mm away from rhizosphere in the ME, and significantly higher in the range of 4 mm and 2 mm away from rhizosphere in the NME than those in the bulk soil. The concentration of NaHCO₃-Po and NaOH-Pi, NaOH-Po in soil were significantly lower than those in the bulk soil in 6 mm away from the rhizosphere of the two ecotypes. There was no significant difference of soil HCl-Pi, HCl-Po and residual-P between rhizosphere microdomain and bulk soil. The concentration of NaHCO₃-Pi in rhizosphere microdomain of ME was significantly lower than that of NME under the treatment of no N application and suitable N application, and the utilization ability of soil NaHCO₃-Pi of the ME was stronger. 3) Under suitable N application treatment, the activities of phosphatase in rhizosphere soil of two ecotypes of Pilea sinofasciata were higher than that without N application. The activities of soil acid phosphatase and alkaline phosphatase were significantly higher in the microdomain 4 mm and 2 mm away from the rhizosphere than those in the bulk soil, and the phytase activity in the microdomain 8 mm away from the rhizosphere was significantly higher than that in the bulk soil. The soil phosphatase activity in the rhizosphere microdomain of the ME were higher under the treatments of no N application and suitable N application.  【Conclusions】  Under high P condition, suitable N application increased the activities of soil phosphatase in the rhizosphere microdomain of both two ecotypes of Pilea sinofasciata, and the activities of soil phosphatase in the rhizosphere microdomain of the ME were higher, which was conducive to the transformation of soil P in the rhizosphere microdomain from low-availability fractions to high-availability fractions, and promoted plant growth and P accumulation.