旱地夏闲期间土壤氮素矿化特性的变化

采用间歇淋洗好气培养法测定了黄土区旱地不同土壤及施氮量下夏季休闲前后土壤氮素矿化累积量,分析了旱地夏休闲期间土壤氮素矿化特性的变化。结果表明:与休闲前相比,休闲后土壤氮素矿化累积量显著降低,长武及杨凌试点土壤分别降低了29.52%及7.15%;长期不施氮肥处理休闲后土壤累积矿化氮量显著降低,而长期施用氮肥处理休闲前后土壤累积矿化氮量间的差异未达显著水平。相关分析表明,休闲前土壤氮素矿化累积量与土壤有机质、全氮含量间有显著正相关关系。采用双组分一级动力学方程拟合的土壤易矿化氮矿化势休闲前后长武及杨凌试点土壤分别降低了85%及66%,可见夏季休闲显著促进了旱地土壤易矿化氮的矿化。

Change of soil nitrogen mineralization in dryland during the summer fallow

The Stanford and Smith aerobic incubation method was used to study the changes of nitrogen (N) mineraization from soils from farmer''s fields and by nitrogen application treatments before and after summer fallow in the Loess Plateau. Compared to that before summer fallow, soil N mineralization after summer fallow in Changwu and Yangling was decreased by 29.52% and 7.15%, respectively. The cumulative mineralized N also was decreased significantly in long-term non-N fertilization after summer fallow. However, significant differences were detected for the two different N fertilization treatments. Correlation analysis showed significant positive correlations between the cumulative mineralized N and soil organic matter and total N before summer fallow. Two pools of first-order kinetic equation were used to model the curves of N mineralization from different soils. The results indicated that mineralized N potential (N₁) in soils of Changwu and Yangling after summer fallow were decreased by 85% and 66%, respectively. Therefore, summer fallow significantly reduced the mineralization of N in soil.