施肥处理对黄土丘陵区农田土壤酶活性和水溶性有机碳、氮的影响

为了评估长期施肥处理对黄土丘陵区川地农田土壤酶活性以及水溶性碳、氮的影响,以黄土高原安塞站川地农田定位试验样地为研究对象,分析了以土壤脲酶、蔗糖酶、碱性磷酸酶和过氧化氢酶的酶活性和单位有机碳酶活性作为评价微生物活性新途径的可行性,以及土壤水溶性有机碳、总氮和水溶性碳氮比的变化特征.试验共设九个处理,分别为N(氮肥)、P(磷肥)、M(有机肥,羊粪)、N+P、N+M、P+M、N+P+M,另加空白对照CK(不施肥)和裸地BL(无作物,不施肥).试验结果表明,除了过氧化氢酶,其他三种土壤酶活性都是表层高于下层,而且有机肥参与的处理土壤酶活性要显著高于化肥处理.初步分析发现有机质含量越高,单位有机碳酶活性值越低.长期施用有机肥,可显著提高土壤中水溶性有机碳和水溶性氮的含量,WSOC/WSTN对于不同施肥处理的响应要比C/N更为敏感.相关分析表明,水溶性有机碳、水溶性氮和有机质、全氮、碱解氮与脲酶、蔗糖酶、磷酸酶三种酶都达到极显著相关关系,与过氧化氢酶未达到显著相关.总体研究发现,施化肥并不能显著影响土壤酶活性,但有机肥能显著提高土壤酶活性及水溶性碳、氮含量,施肥方式的差异影响着土壤酶活性;单位有机碳酶活性的响应规律和传统酶活性的规律并不一致,其机理还需进一步研究.

Effects of Fertilization on Soil Enzyme Activities and Water-soluble Organic Carbon and Nitrogen Content in Farmland on Hilly Loess Plateau

Changes of soil enzyme activities and water soluble organic matter content were examined under different fertilizer regimes in a long-term experiment located in an alluvial terrace farmland at the Ansai Field Research Station in the hilly Loess Plateau region. The fertilization treatments included chemical nitrogen(N), chemical phosphorus(P), manure(M), N+P, N+M, P+M, N+P+M, CK(control, no fertilization) and BL(bare land). Soil samples were collected from 0~20 cm and 20~40 cm depths. Soil urease, invertase, alkaline phosphatase and catalase activities, water soluble organic carbon(WSOC) and water soluble total nitrogen(WSTN) content were determined. Soil urease, invertase and alkaline phosphatase activities were higher in surface soils than in deeper soils and greater under long-term organic fertilization than under inorganic fertilization. Long-term application of organic manure increased the content of WSOC and WSTN. The ratio of WSOC:WSTN was more sensitive to different fertilizers than C:N ratio was. WSOC, WSTN, organic matter, total nitrogen and available nitrogen were significantly positively correlated with urease, invertase and alkaline phosphatase. Applying inorganic fertilizers did not influence soil enzyme activities significantly, while supplying organic manure significantly increased enzyme activities and WSOC and WSTN content. The responses of enzyme activities per unit carbon to different fertilization were not consistent with previous research results. Further research should be conducted to understand the mechanisms of responses of soil enzyme activities to fertilization.