长期施肥条件下华北平原农田硝态氮淋失风险的研究

Study of nitrate leaching potential from agricultural land in Northern China under long-term fertilization conditions

利用河北辛集潮土(21年)和北京昌平褐潮土(9年)两个长期定位施肥试验研究了华北平原冬小麦夏玉米轮作体系下农田氮素平衡和硝态氮淋失风险。结果表明,单施氮肥的增产效果有限,昌平试验点甚至出现减产现象;而适量有机肥与氮磷或氮磷钾配施可显著提高作物产量,降低氮素盈余。单施氮肥时,辛集和昌平土壤硝态氮峰值分别达20.7和30.0 mg/kg,出现在160—200 cm和90—120 cm土层;硝态氮累积量高且大部分集中在根区外土壤,硝态氮淋失风险大。氮磷或氮磷钾肥配施时,硝态氮峰值出现深度上移30—40cm,根区和根区外土壤硝态氮累积量均大幅降低,淋失风险明显减弱;在氮磷或氮磷钾肥基础上适量施用有机肥时,硝态氮峰值出现深度进一步上移至根区土壤,深层土壤硝态氮累积量显著下降,淋失风险低。过量施用有机肥或过量施用氮肥时,深层土壤硝态氮累积量大幅增加,甚至超过单施氮肥处理,淋失风险大大增强。研究结果表明,氮磷钾肥与有机肥配合施用是提高作物产量、控制农田硝态氮淋失的重要途径。

N balance and the potential of nitrate leaching loss（PNLL） under winter wheat and summer maize rotation system in Northern China was studied with two long-term fertilization experiments, one is at fluvo-aquic soil in Xinji County of Hebei Province with 21 years and another is at brown fluvo-aquic soil in Changping District of Beijing City with 9 years. It was shown that crop yield was lowest under CK treatment and somewhat can be increased by P or PK fertilization. Single N application has little positive effect on crop yield which even brought on negative effect in Xinji experiment. As a result, N surplus was as high as 137 and 212 kg/ha per year under single N fertilization for Xinji and Changping respectively. Crop yield was remarkably increased under NP or NPK fertilization, but N surplus still remain at a lower level even though N uptake improved. When suitable amount of manure was applied combined with NP or NPK fertilizer, crop yield reach very high, but excessive manure application almost has no influence on crop yield, but N surplus can be as high as 227 and 231 kg/ha per year for the two experiments, even much higher than that of single N fertilization. The PNLL was most serious when only N fertilizer was applied in the two sites, as shown that the peak of nitrate content （PNC） occurred at 160-200cm and 120-160cm in soil profile and most of that was in the deep soil layer. When P or PK was applied with N fertilizer, the PNC went upwards for 30-40cm, also nitrate cumulation was sharply decreased both inside and outside the root zone, thus the PNLL was lowered down remarkably. When suitable amount of manure was applied with NP or NPK fertilizer, the NPC went up to 0-90cm, nitrate cumulation outside the root zone was continuously lowered down, the PNLL was very weak. But when excessive manure or N fertilizer was applied, much more nitrate was accumulated in the deep soil layers and the PNLL became much stronger. Heavy soil texture could lower the PNLL. It can be inferred that balanced fertilization is not only an effective way for increasing crop yield, but also a practical measure to control nitrate leaching loss in field scale.