不同形态氮素对玉米秸秆腐解与养分释放的影响

为研究不同形态氮素对玉米秸秆腐解和养分释放的影响，采用尼龙网袋法进行室内堆腐试验，通过外源添加碳酸氢铵、硫酸铵、硝酸钙、尿素和谷氨酸等不同形态氮素调节玉米秸秆C/N（25：1），以不添加氮素处理为对照（CK）。结果表明，随着培养时间的延长，添加不同形态氮素处理的玉米秸秆质量残留率逐渐降低，谷氨酸、硫酸铵和碳酸氢铵均能促进玉米秸秆的降解，其中谷氨酸对玉米秸秆的促腐作用最强，腐解速率常数达到2.8×10^-2 d^-1。尿素对玉米秸秆腐解无明显影响，硝酸钙一定程度上减缓了玉米秸秆的腐解。玉米秸秆腐解过程中养分释放率呈钾>磷>氮的规律。随着培养时间的延长，添加不同形态氮素处理的玉米秸秆碳、氮、磷和钾素质量残留率逐渐降低。培养到180 d时，玉米秸秆残余物中碳、氮、磷和钾素残留质量分别是其初始质量的16.9%~24.8%、21.57%~51.27%、22.72%~59.00%和24.86%~54.48%，其中谷氨酸对玉米秸秆碳、氮和钾素释放促进作用最强，其释放速率常数分别为1.37×10^-2、7.15×10^-3 d^-1和5.62×10^-3 d^-1；而硫酸铵能够促进秸秆中磷的释放，其释放速率常数为7.94×10^-3 d^-1，高于CK处理（7.54×10^-3 d^-1）。研究表明，谷氨酸会提高玉米秸秆的腐解速率与碳、氮和钾素的释放，硫酸铵会提高玉米秸秆的腐解速率与碳、氮、磷素的释放，碳酸氢铵会提高玉米秸秆的腐解速率与氮素的释放，尿素和硝酸钙会促进碳、氮、钾养分的释放，谷氨酸和硫酸铵的促腐效应高于其他形态氮素处理。从还田秸秆快速腐解和养分释放及高效利用角度考虑，秸秆还田后施用谷氨酸和硫酸铵效果最佳。

Influences of different forms of nitrogen fertilizer on the decomposition and release of nutrients from corn straw residue

The effects of different forms of nitrogen fertilizer on decomposition and nutrients released from corn straw residue were simulated in the laboratory to determine how decomposition could be accelerated. There were six treatments of corn straw residues mixed with different forms of nitrogen including ammonium bicarbonate, ammonium sulfate, calcium nitrate, urea, glutamate, and CK. All treatments were conducted with the carbon-to-nitrogen ratio set to 25:1 in net bags in the laboratory. The residual mass of the corn straw slowly decreased with the incubation time throughout the 180-d incubation period. Nitrogen added as ammonium bicarbonate, ammonium sulfate, and glutamate accelerated the decomposition of corn straw, and the decomposition rate of corn straw with glutamate addition was higher than those of all other nitrogen forms at 2.8×10^-2 d^-1. Urea did not have a significant influence while calcium nitrate inhibited decomposition in a certain degree. The release of nitrogen, phosphorus, and potassium from corn straw residues followed the order potassium > phosphorus > nitrogen for the different nitrogen treatments. The residual levels of carbon, nitrogen, phosphorus, and potassium in the corn straw residues decreased slowly with the increase of incubation time. After 180 d of incubation, the proportion of residual masses of carbon, nitrogen, phosphorus, and potassium were 16.9%~24.8%, 21.57%~51.27%, 22.72%~59.00%, and 24.86%~54.48%, respectively, of the initial mass in the corn straw residue. Nitrogen in glutamate was found to greatly promote the release of carbon, nitrogen, and potassium from corn straw residues at decomposition rates of 1.37×10^-2 d^-1, 7.15×10^-3 d^-1, and 5.62×10^-3 d^-1, respectively. Ammonium sulfate accelerated the release of phosphorus from the corn straw residues, at a decomposition rate of 7.94×10^-3 d^-1, which was higher than that of CK(7.54×10^-3 d^-1). The addition of all different forms of nitrogen, except calcium nitrate, accelerated the decomposition of and release of carbon, nitrogen, phosphorus, and potassium from corn straw residues. Nitrogen in glutamate and ammonium sulfate had a greater impact on this than other forms of nitrogen. Based on the decomposition rate and the nutrients released and their utilization, glutamate and ammonium sulfate are the best candidates for use on corn straw residues after their return to agricultural fields.