秸秆还田和施氮对农田土壤呼吸的影响

The effects of crop residue amendment and N rate on soil respiration

2003年10月至2004年9月期间在华北平原冬小麦-玉米轮作的高产粮区开展了土壤温度、秸秆还田和施氮对农田土壤呼吸影响的研究.土壤类型是砂姜黑土.试验共设6个处理,分别是N1、N1+W、N2+W、N3+W N1+W+O和N2+W+M,其中N1、N2和N3表示3个施氮水平(纯N计,下同),分别是200 kg hm-2、400 kg hm-2和600 kg hm,W表示小麦秸秆还田,M表示玉米秸秆的1/3还田,O表示施用有机肥(每年施用鸡粪30 m3hm-2).土壤呼吸采用碱液吸收法测定,每个处理6次重复,结果表明:(1)土壤呼吸季节动态明显,夏季高冬季低,土壤呼吸排放速率与5cm深度地温线性拟合最好(R2=0.63～0.74,p＜0.001),而与地表温度线性拟合最差.各处理土壤呼吸的年通量在5650～7061 kg·hm-2(纯C计,下同),随着秸秆还田量的增加,土壤呼吸通量显著增加(p=0.05),随着施氮量的增加土壤呼吸通量也增加,但只有施氮量相差400 kg hm-2时,土壤呼吸通量差异显著(p=0.05),施用有机肥的处理土壤呼吸通量最高,有机肥施用后1～2个月,有机肥快速分解,表现为高的土壤呼吸通量.由土壤呼吸与5cm深度地温指数拟合方程求得的Q10值在1.86～2.26之间.

This study was conducted to examine the effects of N fertilization and amendments of crop residue on soil respiration in a farm with winter wheat-maize rotation in the North China Plain during Oct. 2003 - Sept. 2004. Six treatments included N1, N1＋W, N2＋W, N3＋W, N1＋W＋O, and N2＋W＋M, where N1, N2, and N3 （Pure N, the same below） were 200, 400, and 600 kg hm^-2 a^-1, respectively; W was the amendments of wheat residue; M was the amendments of maize residue; and O was 30 m^3 chicken manure hm^-2 a^-1. Soil respiration was measured using alkali absorption method with six replicates for each treatment. Soil respiration had obvious seasonal variation, with the highest flux in summer and the lowest flux in winter. Soil respiration showed positive correlation with soil temperature at 5 cm depth （R2= 0.63-0.74,p（ 0. 001） with temperature sensitivity （Q10） varying from 1.86 to 2.26. Total annual soil respiration was ranged from 5650-7060 kg hm^-2（pure C, the same blow）. Both manure application and amendments of crop residue had significantly positive impacts on soil respiration. There was significant difference in annual soil respiration under fertilization treatments of 200 kg hm^-2 and 600 kg hm^-2. However, soil respiration under fertilization treatment of 400 kg hm^-2 showed no difference with those under 200 kg hm^-2 or 600 kg hm^-2. Soil respiration was the highest in the N1＋W＋O treatment, and occurred during 1-2 months after manure application. Our results suggest that enhanced soil respiration may offset the potential increment in soil organic carbon under manure application and amendments of crop residue.