摘要：
The boosting regression tree method was used to analyze provincial variation of TN loss intensity of farmland during 2012-2014 and its affecting factors, of which contribution rates were calculated. Furthermore relationships of the intensity with the factors were analyzed. Results show that the mean loss intensity of the period of 2012-2014 was in the range of 9. 40-9. 50 kg·hm-2 in the country. North China, South China, and East China was relatively high, with mean of the three years being 16. 51, 15. 16 and 14. 01 kg·hm-2 , respectively, whereas Northeast China, Southwest China and Northwest China was relatively low with mean being 3. 41, 7. 02 and 8. 18 kg·hm-2, respectively. Factors affecting the intensity were found including structural, technical and regional ones, of which the contribution rate reached 20. 9%, 28. 5% and 42. 6%, respectively. Obviously, regional factor was the major one and the highest in influencing degree. North China, South China, East China and Central China, where soil N in farmland is more liable to get leached, are the focal points for N loss control. Ratio of cereal crops and vegetable in area, nitrogen fertilization intensity and ratio of effec-tive irrigated farmlands in area were also factors positively affecting the intensity, while multiple cropping index, farming output value per capita, and farmland area per capita were negative factors. It is, therefore, recommended to readjust or optimize agricultural structure, water and fertilizer management and land use in the light of the natural and socio-economic conditions of the region, so as to reduce the loss intensity of soil TN from the farmland.%采用增强回归树(boosting regression tree,BRT)方法分析我国2012—2014年农田总氮流失强度省际差异的影响因素,测算各影响因素的贡献率,分析农田总氮流失强度与各影响因素的关系.结果表明:2012—2014年我国农田总氮流失强度年平均值为9.40~9.50 kg·hm-2,其中,华北、华南和华东地区农田总氮流失强度较高,3年平均值分别为16.51、15.16和14.01 kg·hm-2;农田总氮流失强度较低的地区是东北,3年平均值为3.41 kg·hm-2,其次是西南地区(7.02 kg·hm-2)和西北地区(8.18 kg·hm-2).结构因素、技术因素和区域因素对农田总氮流失强度省际差异的贡献份额分别为20.9%、28.5%和42.6%.区域因素对于农田总氮流失强度省际差异的贡献最大,影响程度也较大,华北、华东、华南和华中地区农田氮素更容易流失,是农田总氮流失的重点控制区.粮食作物和蔬菜播种面积比例、氮肥投入强度和有效灌溉面积比例对农田总氮流失强度的影响总体上呈增加趋势,复种指数、人均种植业产值和人均耕地面积的影响则总体上呈减少趋势.建议根据区域自然地理条件和农业经济特征,通过优化农业结构、统筹水肥管理和改善土地利用来降低氮肥投入强度和提高氮肥利用效率,从而削减农田总氮流失强度.
