有机肥化肥配施对红壤丘陵区稻田土壤氮淋失特征的影响

Impact of Combined Manure and Chemical Fertilization on Nitrogen Leaching from Paddy Field in Red Earth Hilly Area of China

化肥过量施用导致土壤养分累积引起的氮（N）磷（P）淋失是农业面源污染的重要形式。基于有效提高养殖废弃物的资源化利用率和保护地下水水质等目的，通过田间小区试验研究了有机肥（M）与化肥（F）不同配施比例对100 cm深度稻田土壤N淋失特征的影响。结果表明：在整个晚稻生长期内，渗漏水中不同形态溶解态N浓度的动态变化不尽一致，其中总氮（TN）和铵态氮（NH＋4-N）的浓度在每次施肥之后1~3 d出现淋失高峰，最大分别达到1.985、1.165 mg N·L-1，而硝态氮（NO-3-N）浓度的变化比较平缓，无明显峰值。就组成成分而言，NH＋4-N为淋失TN的主要成分，平均占54.2％；其次是有机态氮（ON），占45.1％；NO-3-N浓度很低（〈0.2 mg N·L-1），仅占0.7％。随着有机肥比例的增高，晚稻产量表现为显著（P〈0.05）的先增后降变化趋势，与TN及NH＋4-N淋失量和淋失率的变化趋势相似，但N的峰值比产量略有滞后。综合考虑施肥的增产作用与土壤N的淋失风险，研究区稻田化肥与有机肥的配比采用7：3较为适当。

Excessive applications of chemical fertilizers cause nitrogen（N）and phosphorus（P）leaching and thus agricultural non-point source pollution. Here, we conducted a field experiment to study the impact of manure（M）and chemical fertilizer（F）combination on soil N leaching at a depth of 100 cm in paddy field in red earth hilly area, Hunan Province of China. The results showed that the peak concentra-tions of total nitrogen（TN）and ammonium nitrogen（NH＋4-N）in leachates occurred 1~3 d after fertilizer addition and the maximum values were 1.985 mg N·L-1 and 1.165 mg N·L-1 for TN and NH＋4-N, respectively. However, nitrate（NO-3-N）concentrations in the leachates were at a relatively low level（〈0.02 mg N·L-1）and varied little without any obvious peaks. Of TN in the leachates, NH＋4-N was the main form （54.2%）, followed by organic nitrogen（45.1%）and NO-3-N least（0.7%）. The grain yield of late rice increased in treatments with manure ratios of 0 to 30%, but decreased with 30%to 60%of total nitrogen addition. Leaching amounts and rates of TN and NH＋4-N showed similar trends during growth of late rice. Taking into consideration of rice yield and leaching risk of soil N, an application ratio of 7：3 chemical to manure fertilizer is recommended in the studied area.