华北山前平原农田土壤养分循环的酶学调控

Enzymological regulation of soil nutrient cycle in the piedmont region of North China Plain

土壤酶是推动土壤养分循环的生物催化剂,研究华北山前平原农田养分循环的酶学调控机制将有助于评价该地区土壤养分状况。试验用土壤取自中国科学院栾城农业生态系统试验站,分析了土壤脲酶与碱性磷酸酶活性在0-10 cm、10-20 cm、20-30 cm和30-40 cm 4个土层中的分布,研究了土壤粗砂(2 000-200μm)、粉砂(200-63μm)、粉粒(63-2μm)和黏粒(2-0.1μm)4个颗粒组中土壤酶活性与土壤养分之间的相关性。研究结果表明:土壤脲酶活性与碱性磷酸酶活性均随土壤深度增加而降低,土壤酶活性随土壤粒径减小而升高。在土壤粗砂和粉砂组分中,土壤酶活性与养分含量显著相关,而在土壤粉粒和黏粒组分中,土壤酶活性与土壤养分含量并不总是显著相关。这些结果说明:土壤酶活性在土壤养分循环中起到重要的调控作用,土壤粗砂和粉砂中的土壤酶具有较高的田间实际催化活性,对土壤养分循环的贡献较大;与此相反,土壤粉粒和黏粒中的土壤酶由于土壤无机矿物的吸附作用而失去部分田间催化能力,降低了其对土壤养分循环的贡献。

Soil enzymes are the biochemical catalysts of soil nutrient cycle.Research efforts on enzymological mechanisms of soil nutrient cycle are vital in evaluating the state of soil nutrients in the piedmont region of North China Plain（NCP）.The objectives of the study were to investigate： i） the distributions of soil enzyme activity in the soil profile and ii） the correlations between soil en-zyme activity and nutrient content of different particle-size fractions.The soils were collected from long-term field experimental plots at the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences.The distributions of soil urease and alkaline phosphatase activities in the 0-10 cm,10-20 cm,20-30 cm and 30-40 cm soil layers were analyzed.Then the collected soil samples were grouped into coarse sand（2 000-200 μm）,fine sand（200-63 μm）,silt（63-2 μm） and clay（2-0.1 μm） fractions using low-energy sonication.Next the correlations among soil enzyme activities and soil nutrients contents were determined for the coarse sand,fine sand,silt and clay fractions.The results showed that the activities of soil urease and alkaline phosphatase decreased with increasing soil depth and increased with decreasing particle size.Enzyme activities were significantly correlated with soil nutrient content in coarse and fine sand fractions,but not so much correlated in the silt and clay fractions.These results suggested that soil enzyme activities were important driving factors of soil nutrient cycle.The enzymes in coarse and fine sand fractions promoted in situ catalytic activities and contributed greatly to soil nutrient cycle.On the contrary,enzymes in the silt and clay fractions inhibited in situ catalytic activities via soil mineral absorption,limiting their contribution rate to soil nutrient cycle.