太湖流域农田生产-畜禽养殖系统氮素流动特征

Nitrogen Flow Features of Crop-Livestock Breeding System in Taihu Lake Basin

为应对太湖严峻的水体富营养化现状,从源头上降低面源污染负荷,基于物质流分析法与质量守恒原理,研究了常熟市辛庄镇农田生产-畜禽养殖系统的氮素流动通量、流动效率及环境负荷,并用实测值进行了参数校正.结果表明:2000—2012年,辛庄镇农田生产子系统的单位面积氮素流动通量呈下降趋势,而畜禽养殖子系统的单位面积氮素流动通量则在42.5~50.9kg/hm^2范围内持续波动.氮素利用率与氮素循环利用率均较低,氮素环境损失率较高,系统损失的氮素中有54.5%进入周围水体.2000年以来,作物种植与畜禽养殖对辛庄镇环境氮负荷的贡献率分别在38.8%~50.2%与25.4%~35.8%之间波动.辛庄镇农田施氮量为310.8 kg/hm^2,人畜排泄氮量为61.1 kg/hm^2,分别远高于全国平均值(197.2和18.6 kg/hm^2).过量施用化学氮肥与畜禽粪便的大量排放是辛庄镇环境氮负荷加重的主要原因.辛庄镇高投入高产出的农业生产方式加大了太湖水环境修复的难度.建议调整作物种植与畜禽养殖结构,推广科学施肥与生态养殖,将农田生产与畜禽养殖结合形成产业链,以此减轻氮素环境负荷.

In order to confront the severe eutrophication of Taihu Lake and radically reduce non-point source pollution,based on material flow analysis and the principle of mass conservation,we studied the nitrogen flow flux,efficiency and environmental load of the ＂croplivestock breeding＂system in Xinzhuang Town and regulated the parameters using the measured values. From 2000 to 2012,nitrogen flow flux of the crop production subsystem in Xinzhuang Town showed a declining trend,while the nitrogen flow flux of the livestock breeding subsystem represented a continuous wave between 42. 5 and 50. 9 kg/hm^2. Both nitrogen use efficiency and recycling rate were low;moreover,the rate of nitrogen loss to the environment was high. The percent of nitrogen loss into the surrounding water was 54. 5% in the system. Since 2000,the proportions of the crop production and livestock breeding contributing to the environmental nitrogen load were38. 8%-50. 2% and 25. 4%-35. 8%,respectively. The amount of nitrogen used in farmland and excreted by livestock was 310. 8 kg/hm^2and 61. 1 kg/hm^2,respectively,which were well above the average values at the national scale（ 197. 2 and 18. 6 kg/hm^2）. Excessive use of chemical fertilizer and massive emissions of livestock excreta were the main reasons for aggravated environmental nitrogen load in the region. The ＂high input-high yield ＂ mode of the agricultural production in Xinzhuang Town significantly enhances the difficulty of water environment restoration in Taihu Lake. Suggestions were proposed to relieve the environmental load of nitrogen,such as regulating the structure of crop and livestock production,promoting scientific fertilization and ecological breeding,combining crop production with livestock breeding to form