农业氮素投入与农业面源污染风险的响应关系——以河南省为例

Exploring the connection between agricultural nitrogen input and agricultural non-point source pollution risk:a case study of Henan Province

研究以减少面源污染风险、提高氮肥利用效率为目的,根据土壤氮素平衡原理,使用清单分析法和排污系数法解析了河南省17个地级市氮肥施用现状并对各地市农田土壤氮盈余、理论施氮量以及监控施氮量进行了量化分析。结果显示:除漯河市外,河南省剩余16个地级市的农田土壤氮素含量普遍处于盈余状态,氮盈余平均值达到255 kg/hm^(2),氮肥生产效率较低且大量施肥,是导致河南省农业面源污染和制约粮食增产增效的主要原因;河南省16个地级市存在过量施氮的情况,对作物施氮量进行调整后,在保证土壤养分和作物生产的前提下,河南省年总施氮量由原来的3.793×10~6 t减少到2.553×10~6 t,平均施氮量负荷由455 kg/hm^(2)降低到319 kg/hm^(2),河南省平均氮肥生产效率也将从14.3 kg/kg提升到22.3 kg/kg,有效提高了氮肥生产效率并减少了农业面源污染发生的风险;在农田土壤氮素平衡模型中,濮阳市、焦作市等部分施氮水平较高的地区由于土地利用率高、农作物消耗较大和种植结构等原因,农田土壤氮素的过剩量较小,农业面源污染风险也较小;济源、三门峡等部分施氮水平较低的地区由于地形、土壤和熟制等因素影响,农田土壤氮素的过剩量反而较大,农业面源污染风险也较大。因此,施氮量越大并不意味着农业面源污染风险越大,在农业生产中不能一味地追求“减氮”,而是要使氮肥施用量能够满足实际农业生产和增产的需求。

The purpose of this study is to mitigate non-point source pollution risk and enhance nitrogen use efficiency in fertilizer applications.Employing the principles of soil nitrogen balance,this research analyzed nitrogen fertilizer application across 18 cities in Henan Province using list analysis and sewage discharge coefficient methods.The study quantitatively assessed soil nitrogen surplus,theoretical nitrogen application rates,and monitored nitrogen application rates.The findings revealed that farmland across 18 cities in Henan Province generally exhibited a surplus in soil nitrogen content,with an average nitrogen surplus of 255 kg/hm~2.The low nitrogen production efficiency and excessive fertilization emerged as the primary contributors to agricultural non-point source pollution.Moreover,grain production and efficiency in Henan Province decreased from 3.793×10~6 t to 2.553×10~6 t.The average nitrogen application load decreased from 455 kg/hm~2 to 319 kg/hm~2,while the average nitrogen production efficiency in Henan Province increased from 14.3 kg/kg to 22.3 kg/kg.These outcomes effectively enhanced nitrogen fertilizer production efficiency and reduced the risk of agricultural non-point source pollution.Given the substantial crop consumption and planting structure,farmland exhibits minimal soil nitrogen excess,resulting in a low risk of agricultural non-point source pollution.Conversely,in regions like Jiyuan and Sanmenxia with low nitrogen application levels,the surplus of soil nitrogen in farmland is comparatively significant,leading to a higher risk of agricultural non-point source pollution.This risk is further amplified by factors such as topography,soil conditions,and agricultural practices.Hence,the greater the nitrogen application rate,the higher the risk of agricultural non-point source pollution.This underscores the need to avoid blindly pursuing“nitrogen reduction”in agricultural production.Instead,the focus should be on meeting the actual requirements of agricultural production and achieving increased yields.