干湿交替和外源氮对农田土壤CO2和N2O释放的影响

以黄淮海平原潮土区的砂壤土和黏壤土为研究对象,通过培养试验研究了干湿交替(干湿频率分别为0、2、6、12次)和外源氮(2种土壤中添加氮累计量均为220 mg N·100g~(-1)干土)下砂壤土和黏壤土的CO_2和N_2O释放模式的影响。结果表明,干湿交替和外加氮源显著激发了砂壤土和黏壤土的CO_2和N_2O的释放速率:干燥期越长,外加N源对土壤CO_2释放速率的激发效应越强;干燥期越短,外加N源对土壤N_2O释放速率的激发效应越强。两种土壤的CO_2和N_2O的释放速率对干湿交替的响应模式一致,砂壤土的碳氮矿化速率对干湿交替响应更为强烈,砂壤土的可溶性有机碳和无机氮(NO-3和NH+4)含量及温室气体排放速率均高于黏壤土。在外加氮源的条件下,干湿交替显著提高了砂壤土和黏壤土中可溶性有机碳和无机氮的含量,增大了实际生产中农田土壤无机氮淋失和温室气体排放的可能性。

Effects of drying-wetting and additional nitrogen on CO2 and N2O emissions from farmland soils

Under laboratory controlled conditions, the effects of drying-wetting cycles (dry-wet frequency:0, 2, 6 and 12 cycles) and nitrogen addition on soil CO₂ and N₂O release patterns were investigated with soils of fluvo-aquic sandy loam and fluvo-aquic clay loam, which were typical soils in the Huang-Huai-Hai Plain. The results showed that the drying-wetting cycles and nitrogen addition significantly increased the release rate of CO₂ and N₂O in the sandy and clay loam soil. The longer the drying period, the stronger the excitation effect of nitrogen addition on the soil CO₂ release rate, whereas the shorter the drying period, the stronger the excitation effect of nitrogen addition on the soil N₂O release rate. There were similar response patterns of soil greenhouse gas (CO₂ and N₂O) release rates to the drying-wetting cycle between the two cropland soils. Compared with the clay loam soil, the sandy loam soil presented a more intense response of carbon and nitrogen mineralization to the drying-wetting cycle. The dissolved organic carbon and inorganic nitrogen content, and the greenhouse gas release rate in the sandy loam soil were significantly greater than that of the clay loam soil. Under the condition of nitrogen addition, the drying-wetting cycle significantly increased the dissolved organic carbon and inorganic nitrogen content in the sandy loam and clay loam soil, which increased the probability of inorganic nitrogen (NO₃^- and NH₄⁺) leaching loss and the green house gases (CO₂ and N₂O) emission in agricultural production.