稻田肥料减施对小麦秸秆腐解规律的影响

以稻田肥料等量减施为背景,研究小麦秸秆在腐解过程中秸秆残余率、氮、磷、钾以及纤维素类碳水化合物的累积释放率和平均释放速率。全氮采用H₂SO₄-H₂O₂消煮-蒸馏法,全磷采用钼锑抗比色法,全钾采用火焰光度计法测定,纤维素、半纤维素、木质素采用分光度计比色法进行测定。计算秸秆的残余率、物质累积释放率、物质平均释放率,并采用修正后的Olson指数衰减模型对秸秆的腐解动态进行拟合。结果表明,施肥会促进小麦秸秆在稻田中的腐解、秸秆残余率的降低,采用修正后的Olson指数衰减模型对秸秆腐解进程的模拟显示,CK和F₅₀处理下秸秆腐解50%的理论预测时间比CK₀处理分别缩短22天和12天,CK和F₅₀处理下秸秆腐解95%的理论预测时间比CK₀处理分别缩短95天和59天,施用肥料可促进秸秆中氮、磷、钾及纤维素类碳水化合物的累积释放率和平均释放速率,其中,肥料减施对钾素累积释放率影响最小,秸秆中氮磷钾养分前期的平均释放速率相对较快,纤维素、半纤维素和木质素的秸秆释放周期较长。稻麦轮作系统中,施用肥料可促进小麦秸秆的氮、磷、钾及纤维素类碳水化合物的累积释放率和平均释放速率。研究结果可为小麦秸秆肥料化利用提供理论支持。

Effects of Rice Field Fertilizer Reduction on Wheat Straw Decomposition

The cumulative release rate and average release rate of straw residues, nitrogen, phosphorus, potassium and cellulosic carbohydrates during the decomposition of wheat straw were investigated under the condition of the same amount of fertilizer reduction in rice field. Total nitrogen was determined by H₂SO₄-H₂O₂ digestion-distillation method, total phosphorus by molybdenum-antimony anticolorimetry, total potassium by flame photometric method, cellulose, hemicellulose and lignin by colorimetric method. The residual rate, cumulative release rate and average release rate of straw were calculated, and the decay dynamics of straw were fitted with modified Olson exponential decay model. The results showed that fertilization could promote the decomposition of wheat straw in the rice field and reduce the residual rate of straw. Meanwhile, the modified Olson exponential decay model was used to simulate the decomposition process of straw. It was shown that the theoretical prediction time of 50% straw decomposition under CK and F₅₀ treatment was shortened by 22 days and 12 days respectively compared with CK₀ treatment. The theoretical prediction time of 95% straw decomposition under CK and F₅₀ treatment was reduced by 95 days and 59 days compared with CK₀ treatment, respectively. Fertilizer application could promote the cumulative carbohydrates release rate and the average release rate of straw nitrogen, phosphorus, potassium and fiber, in which, the fertilizer reduction had the least effect on the cumulative release rate of potassium, the average release rate of NPK nutrients was relatively quick in the early stage, cellulose, hemicellulose and lignin had longer release period. In rice-wheat rotation system, fertilizer application could promote the cumulative and average release rate of N, P, K and cellulose carbohydrate of wheat straw, and the study could provide theoretical support for fertilizer utilization of wheat straw.