太湖流域典型农业区氮平衡时间变化特征及驱动因素

Temporal Changes of Nitrogen Balance and Their Driving Factors in Typical Agricultural Area of Lake Tai Basin

利用1985~2011年分县统计数据,基于土壤氮平衡模型,研究了太湖流域典型农业区氮平衡的时间变化特征。结果显示,1985~2011年,太湖流域典型农业区氮平衡均处于盈余状态,但不同农业区氮盈余强度的时间变化特征不同。在1985~1999年间除几个特殊年份外,常熟农业区氮盈余强度变化相对平稳,而在2000~2011年间呈逐年增加的趋势;宜兴、太仓、桐乡农业区在1985~1995年间稳定增加,而自1996年以后呈明显的下降趋势;长兴、安吉、嘉善农业区在1985~1995年间明显增加,1996~1999年间有所下降,2000~2011年间趋向稳定。在太湖流域典型农业区氮平衡中,氮输入源以化肥输入为主,约占总氮输入量的76.8%;其次为生物固氮,约占总氮输入量的8.9%;大气沉降、秸秆还田和人畜排泄物所占比例较小,分别为5.8%、4.5%和4.0%。氮输出项以作物收获带出为主,约占总氮输出量的54.1%,反硝化和氨挥发分别占21.6%和17.9%,氮流失和淋失共占6.4%。分析表明,太湖流域典型农业区氮平衡时间变化的差异主要与当地的农业政策实施、农业技术进步和城市化进程有关,区位经济、农业生产方式和农业受重视程度也是导致不同农业区氮平衡差异的重要驱动因素。

By using the statistical data of seven counties during 1985 ~ 2011, the temporal changes of nitrogen balance in typical agricultural area in Lake Tai Basin was analyzed based on agricultural soil nitrogen balance model.It showed that agricultural nitrogen balance was in surplus for all the study area during 1985 ~ 2011, but the nitrogen surplus intensity differed spatially. Changshu changed steadily in 1985 ~ 1995 except some special years, but presented an increasing trend after 1996. Yixing, Taicang and Tongxiang increased steadily in 1985 ~ 1995 but decreased evidently after 1996. Changxing, Anji and Jiashan increased evidently in 1985 ~ 1995, decreased relatively in 1996 ~ 1999, and presented a stable trend in 2000 ~ 2011. As to nitrogen sources, chemical nitrogen fertilizer application was the biggest contributor, which accounted for about 76.8% of total agricultural nitrogen inputs.Biological nitrogen fixation accounted for about 8.9%. Atmospheric nitrogen deposition, crop residues and manure nitrogen from human and domestic animals accounted for 5.8%, 4.5% and 4.0%, respectively. As to nitrogen output items, crop harvest export accounted for about 54.1% of total agricultural nitrogen outputs. The nitrogen loss through denitrification and ammonia volatilization accounted for about 21.6% and 17.9%, respectively. The nitrogen loss through runoff and leaching accounted for about 6.4% altogether. The temporal characteristics of nitrogen balance were mainly correlated with local agricultural policy, agricultural technique level and urbanization process. Location economics and agricultural production and agriculture consideration degree were important driving factors, leading to spatial differences of nitrogen balance in typical agricultural area of Lake Tai basin.