秸秆全量还田下施氮量对秸秆降解及相关胞外酶活性的影响

Effects of nitrogen application rate on straw degradation and related extracellular enzyme activities under total straw returning

该试验采用尼龙网袋原位培养法,研究了冷凉区稻田秸秆全量还田下不同施氮水平(110、120、130、140、150 kg·hm^(-2))的水稻秸秆降解特征以及相关胞外酶活性变化特征。结果表明:在秸秆全量还田但施氮量不同的条件下,水稻秸秆在还田前期(0~20 d)和中后期(71~104 d)的降解率较快,此时秸秆残余物中可溶物质的占比大幅度减少,木质素等物质含量在秸秆残余物中的占比增加;在东北冷凉区水稻生育期内,0~15㎝还田秸秆平均降解率约为55%,15~30㎝还田秸秆平均降解率约为50%;与碳相关胞外酶(αG、βG、CBH、βX)活性普遍高于其他功能胞外酶,且秸秆降解胞外酶活性普遍在中后期(71~104 d)升高。研究表明东北冷凉区水稻秸秆全量条件下,施氮量140kg·hm^(-2)时秸秆降解率的综合效应最好,最佳秸秆还田深度为0~15 cm。

To study the degradation characteristics of rice straw and the changes of related extracellular enzyme activities under different nitrogen application levels(110,120,130,140,150 kg·hm^(-2))in cold and cool areas by using nylon mesh bag in situ culture method.The results showed that the degradation rate of rice straw was faster in the early stage(0~20 d)and the middle and late stage(71~104 d)under the condition of total straw returning but different nitrogen application,and the proportion of soluble substances in the residues of straw was greatly reduced,while the proportion of lignin and other substances in the residues was increased.During the growing period of rice in the cold and cool areas of Northeast China,the average degradation rate of straw in 0~15 cm was about 55%,and that in 15~30 cm was about 50%.The activities of carbon-related extracellular enzymes(αG,βG,CBH,βX)were generally higher than those of other functional extracellular enzymes,and the activity of straw degrading extracellular enzymes generally increased in the middle and late period(71~104 d).The results showed that the comprehensive effect of straw degradation rate was the best when the nitrogen rate was 140 kg.hm^(-2),and the optimal straw returning depth was 0~15 cm in the cold and cool areas of northeast China.