红壤水稻土累积酶活性及养分对长期不同施肥处理的响应

本研究基于鹰潭农田生态系统国家野外科学观测研究站24年的长期定位试验,揭示对照(不施肥,CK)、有机肥(C)、化学氮磷钾肥(NPK)、化学氮磷钾肥+有机肥(NPKC)等不同施肥处理对红壤水稻土酶活性及土壤养分的影响。于晚稻收获后采集各小区耕层土壤,测定红壤水稻土中转化酶、脲酶活性(测定时并设加0.5 ml甲苯与不加甲苯处理)及转化酶动力学特征,同时测定土壤养分含量及微生物生物量碳,分析酶活性与养分含量及微生物生物量碳间的关系,明确土壤中累积酶活性及土壤养分对长期不同施肥处理的响应。结果发现,与对照相比,施肥处理下土壤转化酶活性显著提高了31.3%~131.7%,微生物生物量碳显著提高了84.9%~125.1%;在没有甲苯抑制微生物活性下,施肥处理的转化酶底物蔗糖转化速率增加量提高了89.5%~153.7%,脲酶底物尿素转化增加量提高了59.2%~98.9%,表明微生物显著影响两种累积酶表观酶活性;转化酶活性、脲酶活性与微生物生物量碳呈显著正相关。与对照处理相比,施肥处理显著增加了土壤有机碳(30.1%~36.3%)、全磷(28.6%~102.9%)、速效磷(62.2%~445.0%)、碱解氮(35.9%~56.4%)含量;统计分析显示,转化酶活性、脲酶活性均与碱解氮、有机碳含量显著正相关。与对照相比,各施肥处理土壤的转化酶米氏常数(Km)差异并不显著,而转化酶表观活性(Vmax)及转化系数(Vmax/Km)均显著增加。长期施肥处理增加了土壤养分含量和微生物生物量碳,提高了土壤中累积酶的活性。

Activities of Extracellular Enzymes and Nutrients in Red Paddy Soil Response to Long Term Fertilizations

Based on 24-year long-term field experiment established in 1990 in Yingtan Red Soil Ecological Experiment Station, the experiment included 4 treatments: CK(without fertilization), C(manure), NPK(N,P,K fertilizers), NPKC(NPK plus manure), soil samples were collected. The activities of invertase, urease (adding 0.5 ml toluene and not) and invertase kinetics were determined, and the soil nutrient contents and microbial biomass carbon were measured, in order to analyze the relationships among enzyme activity, soil nutrient and microbial biomass carbon to disclose the response of the activity of extracellular enzyme and nutrients to the long term fertilizations. Compared with CK, application of fertilizers increased the invertase activities by 31.3%–131.7% and microbial biomass carbon by 84.9%–125.1%. Without toluene inhibiting the microorganism activity, the invert rate of the substrate of invertase and urease significantly increased by 89.5%–153.7% and by 59.2%–98.9%, respectively; Microbial biomass carbon had significant positive correlations with the activities of invertase and urease, which imply microorganism significantly influenced the activities of these enzymes. Compared with CK, application of fertilizers increased significantly organic matter (by 30.1%–36.3%), total phosphorus(by 28.6%–102.9%), available phosphorus (by 62.2%–445.0%) and available nitrogen (by 35.9%–56.4%), the activities of soil urease and invertase were positively correlated with the contents of available nitrogen and organic matter. Compared with CK, application of fertilizers increased significantly the transfer coefficient (Vmax/Km) and maximum velocity (Vmax) but influenced little on the Michaelis constant (Km). Long term fertilization increased the soil nutrient contents and microbial biomass carbon, which result in the increase of the activity of the extracellular enzymes.