Increased interest in managing agroecosystems for soil health has led to adoption of conservation management practices such as cover cropping and no-tillage. There is a dearth of knowledge surrounding cover crop residue N cycling and release, impacting subsequent N availability for the cash crop after cover crop termination. The microbial degradation of plant material and subsequent nutrient release is mediated by extracellular enzymes. This study used litter bag methodology to investigate the enzyme activities of three cover crop residues (cereal rye (CR) (Secale cereale L.), hairy vetch (HV) (Vicia villosa Roth), and a CR/HV mixture) in two tillage systems (no-tillage and reduced tillage) during the cover crop decomposition period in a corn (Zea mays L.) agroecosystem. The dynamics and amounts of β-glucosidase (EC 3.2.1.21) and urease (EC 3.5.1.5) enzyme activities on cover crop residue were quantified to determine if enzyme activities or stoichiometry are dependent on litter quality or can indicate N cycling potential. Results revealed that cover crop and tillage significantly impacted urease and β-glucosidase residue enzyme activity dynamics and amounts (p < 0.05). β-glucosidase activity of CR, HV, and a CR/HV mixture decreased by 76 %, 81 % and 77 % during the 2016 decomposition period, respectively. On average, urease activities of cover crop residues and soil ammonium concentrations increased during this period. In 2017, urease activities significantly decreased in all treatments (p < 0.05). β-glucosidase enzyme activity significantly decreased from 38 days after termination to 123 days after termination in all cover crop and tillage treatments (p < 0.05). Urease activities were significantly higher in the tillage treatments compared to no-tillage at the beginning of the 2017 decomposition period (p < 0.05). Soil ammonium concentrations significantly increased by 38 % across all treatments in 2017 during the decomposition period and concentrations were 12 times higher in 2017 at corn maturity compared to 2016. These results indicate potential for cover crops to stimulate residue β-glucosidase activity, suppress urease activity and ammonification, and increase soil N immobilization during corn N demanding growth stages. Furthermore, this study indicates that growers should consider optimum cover crop winter biomass accumulation levels to avoid potential N immobilization.

人们对于管理农业生态系统以促进土壤健康的兴趣日益浓厚，导致人们采取了保护性管理措施，例如覆盖作物和免耕法。覆盖作物残渣氮循环和释放的知识匮乏，影响了覆盖作物终止后经济作物的后续氮素利用率。植物材料的微生物降解和随后的养分释放是由细胞外酶介导的。这项研究使用垃圾袋方法研究了两次耕作中三种覆盖农作物残留物（谷物黑麦（CR）（Secale graine L.），毛v子（HV）（Vicia villosa Roth）和CR / HV混合物）的酶活性。系统期间以玉米覆盖作物分解期间（免耕和减耕）（玉蜀黍L.）农业生态系统。对覆盖作物残渣上β-葡萄糖苷酶（EC 3.2.1.21）和脲酶（EC 3.5.1.5）酶活性的动态和数量进行定量，以确定酶活性或化学计量是否取决于垫料质量或可以表明氮循环潜力。结果表明，覆盖作物和耕作显着影响脲酶和β-葡萄糖苷酶残留酶的动态和数量（p <0.05）。在2016年分解期间，CR，HV和CR / HV混合物的β-葡萄糖苷酶活性分别降低了76％，81％和77％。平均而言，在此期间，覆盖作物残渣的脲酶活性和土壤铵态氮浓度增加。2017年，所有治疗中的脲酶活性均显着下降（p <0.05）。在所有覆盖作物和耕作处理中，β-葡萄糖苷酶的酶活性从终止后的38天显着降低至终止后的123天（p <0.05）。与2017年分解期开始时的免耕相比，耕作处理中的脲酶活性显着更高（p <0.05）。在分解期间，2017年所有处理期间的土壤铵态氮浓度均显着增加了38％，与2016年相比，2017年玉米成熟时的铵态氮浓度比2016年高12倍。这些结果表明，覆盖作物有潜力刺激残留β-葡萄糖苷酶活性，抑制脲酶活性和氨化作用，并在要求玉米生长的玉米生长阶段增加土壤对土壤氮的固定作用。此外，