吉林西部农田生态系统氮平衡及其水环境影响研究

针对吉林省西部地区农田生态系统特点,以1997—2011年统计数据为基础,建立了基于物质守恒原理的氮平衡模型,估算了该地区农田生态系统的氮收支情况,并分析了其对水环境的影响.结果表明:近15年该区氮输入量平均值为56.98×104t·a-1,其中化肥输入氮占总氮的79.59%;氮输出量平均值为42.60×104t·a-1,以作物收获输出为主;氮平衡量变化范围为10.17×104~21.91×104t·a-1,均值为14.38×104t·a-1;氮平衡模型的各项呈增长趋势,受农业生产情况差异的影响,年际间时序变化较大,县市间空间分布差异明显.吉林西部农田生态系统氮平衡表现为盈余状态,氮素的盈余主要受氮肥施用和作物收获影响,农田生态系统氮素的持续盈余并累积对水环境构成一定程度的威胁,借助该区水环境监测数据进行综合分析,受盈余氮素的影响,该区地表水和地下水水质均体现出不同程度的氮超标.

Nitrogen balance of farmland ecosystem in the Western Jilin Province and its effect on water environment

According to the characteristics of farmland ecosystem in the Western Jilin Province, estimation of the N budget of local farmland ecosystem had been made by using the balance model. Principle of mass conservation was applied with the statistics in the period of 1997-2011. In addition, the influence on water environment had also been considered. Results indicated that the mean N input was 56.98×10⁴ t·a^-1 during the recently 15 years. Moreover, chemical N fertilizer accounted for 79.59% of total N input. The mean N output was 42.60×10⁴ t·a^-1, and the agricultural N output was the main output source. The N balance ranged from 10.17×10⁴ to 21.91×10⁴ t·a^-1, and the average was 14.38×10⁴ t·a^-1. All terms in the N balance model showed a rising trend. Resulted from the difference of agricultural product, differences in annual variations and spatial distribution between counties are obvious. Nitrogen balance of farmland ecosystem in the Western Jilin Province showed a surplus state. Nitrogen surplus was mainly affected by nitrogen fertilizer and crop harvest. The continuous nitrogen surplus and accumulation of farmland ecosystem threatened the safety of water environment. Comprehensive analysis by using the water environment monitoring data showed exceeded nitrogen in both surface water and groundwater in different levels with the influence of nitrogen surplus.