小麦氮磷肥长期配施对土壤硝态氮淋溶的影响

 【目的】利用长期肥料定位试验，监测旱地农田土壤硝态氮的淋溶动向，研究施肥量与硝态氮累积量之间的关系，为科学施肥提供参考。【方法】在试验小区0～300 cm土壤剖面中，每20 cm深度取一个土样，1 mol?L-1 KCl浸提后以AA3连续流动分析仪测定硝态氮含量。【结果】单施氮肥土壤硝态氮累积峰出现在80～100 cm土层和300 cm以下土层，当施氮量达到180 kg?hm-2?a-1时，0～300 cm土层硝态氮累积总量相当于8年的施氮量。单施磷肥对土壤硝态氮分布无影响;氮、磷肥配施时，施氮量增加硝态氮累积量显著增加，配施磷肥后可以减少硝态氮累积量，且施氮量越大减少的越多。过量施用氮肥，即使配施磷肥，硝态氮也能发生淋溶并在100～120 cm和240～260 cm土层附近累积;二次多项式回归能够较好地反映氮、磷施用量与土壤硝态氮累积量之间的关系。【结论】长期过量施用氮肥，导致硝态氮大量淋溶并形成两个累积峰，科学合理地配施磷肥可以减少硝态氮淋失;旱地麦田长期施用最大产量施肥量，可能导致硝态氮大量累积在土壤深层。

Nitrate-N Leaching in 23-Year Winter Wheat Field Combined with Application of Nitrogen and Phosphorus

【Objective】 To provide a reference for scientific fertilization in the dry-land，present study on the changing trend of NO3--N leaching and the relationship between NO3--N accumulation and fertilizer rates in the farmland ecosystem based on data of the long-term fertilizer experiment. 【Method】Soil samples were collected per 20 cm in 0-300 cm soil layer, after being extracted with 1 mol?L-1 KCl, the NO3--N concentration in soil was analyzed with AA3 automated flow injection analyzer. 【Result】 When N fertilizer was applied alone, the accumulation peaks of NO3--N occurred in 80-100 cm and below 300 cm soil layer. If the annual rate of N reached 180 kg hm-2, total NO3--N accumulation amount in 0-300 cm soil layer was 8 times the amount of annual N application. When P fertilizer was applied alone, it had no significant effect on NO3--N distribution. NO3--N accumulation amount in the soil enhanced significantly with increasing N application rates. When N and P fertilizer was applied in combination, the application of P fertilizer alleviated NO3--N leaching and the positive effect increased with increasing N application rates. When N rates were excessive, even combined with P fertilizer, NO3--N penetrated into deep soil layer and accumulation peaks were found in 100-120 cm and 240-260 cm soil layers. Quadratic polynomial regression equation could reflect the relationship between NO3--N accumulation and N, P fertilizer rates. 【Conclusion】 When N fertilizer was applied excessively for 23 years, NO3--N penetrated largely into deep soil layer and two accumulation peaks were observed. However, NO3--N leaching could be mitigated by combined application of nitrogen and phosphorus. Long-term fertilizers application at rates for maximum yield would result in a great amount of NO3--N accumulation in deep soil layer in dry-land wheat field.