摘要：

不同土地利用方式的土壤磷素循环特征存在差异性,土壤有机磷在酶解作用下的生物转化是磷素循环过程的重要环节。外源碳氮的投入可能改变土壤磷素的生物转化,对于提高土壤磷素生物活性具有关键作用。为研究外源C、N对不同土地利用方式土壤有机磷和胞外酶活性的影响,采用设施菜田、粮田、草地、森林4种不同土地利用方式的土壤,分别设置对照(CK)、葡萄糖(G,500 mg/kg土壤)、硝酸钾(N,300 mg/kg土壤)、葡萄糖和硝酸钾(GN,500 mg/kg葡萄糖土壤和300 mg/kg硝酸钾土壤)4个处理,进行室内培养试验,研究外源碳氮添加对土壤有机磷和速效磷含量及磷酸酶活性的影响。结果表明:与CK处理相比,添加碳源显著提高了菜田和森林土壤有机磷含量,分别提高了89.7%,40.6%;添加氮源,菜田土壤速效磷增加了14.2%,森林土壤速效磷降低了14.0%;与对照CK相比,添加碳源草地和森林土壤中碱性磷酸酶活性分别降低35.9%,25.5%,但其对菜田和粮田土壤中的碱性磷酸酶活性无显著影响;同时添加外源碳氮相较于CK处理增加了4种土壤的β-葡萄糖苷酶活性,且在菜田和草地土壤中差异显著;在添加碳源的基础上,氮源添加降低草地和森林土壤CO₂累积排放量分别达19.7%,16.5%,但对菜田和粮田土壤的CO₂累积排放量无显著影响。综上所述,在菜田、粮田土壤中,外源碳氮投入后土壤胞外酶活性提升,将有机磷更多地矿化为无机磷,土壤有机碳的含量为影响有机磷在土壤中矿化的主要因素;在草地、森林土壤中,外源碳氮的投入降低了碱性磷酸酶的活性,减缓了有机磷的矿化过程,因此,磷酸酶的活性为影响该土壤有机磷矿化的主要因素。

关键词: 土壤磷, 磷酸酶, 土壤培养, β-葡萄糖苷酶, 土壤有机碳, 碳氮投入

Abstract:

Soil phosphorus(P)cycle are varied in different land use soils.The transformation of soil organic P by hydrolyzing by enzymes is an important process in soil P cycling.The exogenous carbon(C)and nitrogen(N)application can influence on the biological process of soil P,which could play a key role in improving soil P bioavailability.In order to study the effects of exogenous C and N on soil organic P and extracellular enzyme activities in different land use soils,four soils from greenhouse vegetable field,grain field,grassland and forest were collected to conduct the incubation experiment.For each soil,four treatments were designed,including control(CK),glucose(G,500 mg/kg soil),potassium nitrate(N,300 mg/kg soil),glucose and potassium nitrate(GN,500 mg/kg glucose soil and 300 mg/kg potassium nitrate soil).The results showed that the soil organic P in greenhouse vegetable field and forest was increased after adding carbon source,increased by 89.7%,40.6%,respectively,compared to control treatment;with the addition of nitrogen sources,the available P in greenhouse vegetable soil increased by 14.2%,while that in forest soil decreased by 14.0%;compared to control treatment,the activity of alkaline phosphatase in grassland and forest soil decreased by 35.9%,25.5% with the input of carbon source,while that in greenhourse vegetable field and grain field soil had no significant effect;compared to control treatment, the β-glucosidase activity of four soils were increased by adding C and N, and the difference was significant in greenhouse vegetable field and grassland soil; based on the addition of carbon source,N addition reduced the cumulative release of CO₂ in grassland and forest soils by 19.7%,16.5%,respectively,but had no significant effect on that of greenhouse vegetable field and grain field soil.Therefore,in greenhouse vegetable field and grain field soil,the soil extracellular enzyme activity increased significantly after the application of exogenous carbon and nitrogen,and the mineralization of organic phosphorus into inorganic phosphorus was more.The content of soil organic carbon was the main factor affecting the mineralization of organic phosphorus in soil;in grassland and forest soil,the application of exogenous carbon and nitrogen reduced the activity of alkaline phosphatase and slowed down the mineralization process of organic phosphorus,so the activity of phosphatase was the main factor affecting the mineralization of organic phosphorus in the soil.

Key words: Soil phosphorus, Phosphatase, Soil culture, β-glucosidase, Soil organic carbon, Carbon and nitrogen input