太湖地区冬小麦田与蔬菜地N_2O排放对比观测研究

Nitrous Oxide Emission from Winter Wheat and Vegetable Fields in the Taihu Region: A Comparison Case Study

2003年11月8日至2004年6月5日对太湖地区相邻的蔬菜地和稻麦轮作生态系统的冬小麦田,在当季不施肥情况下的N2O排放进行了田间同步对比观测,分析了N2O排放时间变化以及土壤湿度、土壤温度、土壤速效氮含量和农业管理措施对N2O排放的影响。研究结果表明,小麦播种前的耕翻(表层大约7cm土壤旋耕)处理不会明显改变稻麦轮作农田整个旱地阶段的N2O排放总量,但却使小麦生长季初期的N2O排放明显减弱69%(p<0.01,p为相关概率),使小麦生长季后期的N2O排放明显偏高2.6倍(p<0.05),而对其余时间段的N2O排放作用不明显。与长期实行稻麦轮作的旱地阶段农田相比,由稻田改种蔬菜20多年的蔬菜地,其整个观测期的N2O排放总量比免耕处理小麦田同期的排放高85%(p<0.05),比耕翻处理小麦田同期的排放高99%(p<0.01)。蔬菜地N2O排放偏高的原因是土壤速效氮,特别是铵态氮含量明显偏高(p<0.01)。

Based on the contrast observations on the nitrous oxide （N2O） emissions from the adjacent unfertilized vegetable field and winter wheat field of the rice-wheat rotation system in the Taihu region from 8 November 2003 to 5 June 2004, its temporal variation and the effects of soil moisture, soil temperature, available N contents and agriculture management practices were investigated and discussed. The results showed that spiral tillage by about 7cm deep in soil before winter wheat sowing had little significant effect on the total N2O emission during the nonrice period of the rotation cycle, but it periodically impacted the N2O emission fluxes. The tillage reduced the N2O emission fluxes during the early period after wheat sowing by about 68% （p〈0. 01） on average, increased the N2O emission fluxes during the late period of the wheat season by about 2.6 folds （p〈0. 05） on average, and had little effect during the remaindering period. The total N2O emission over the entire investigated period was significantly higher in the vegetable fields than that simultaneously observed in the non-tilled and tilled wheat fields by about 85% （p〈0.05） and about 99% （p〈0.01） , respectively. This difference is most likely attributed to the significantly higher available nitrogen content, especially higher ammonium content in the soil of the vegetable fields （p〈0.01）.