小麦-玉米轮作期间不同施肥处理氮素的淋溶形态及数量

利用大型回填土渗漏池研究了陕西关中平原小麦-玉米轮作年生长周期内塿土不同施肥处理氮素淋溶的动态变化。结果表明,小麦-玉米期间土壤淋溶的氮素以硝态氮（NO3--N）为主,溶解性有机氮（DON）次之,铵态氮（NH4＋-N）最低,占淋失总氮的比例平均分别为72.1%、26.2%和1.7%,说明除NO3--N外,DON也是不可忽视的土壤氮素淋失形态。与施氮磷化肥（NP）相比,氮磷化肥和有机肥配施处理（NPM）明显降低了淋溶到100 cm深度土层的氮量;在小麦-玉米生长期间,NPM处理NO3--N、DON和NH4＋-N的累积淋溶量比NP处理分别降低了64.4%、42.9%和54.8%,这与配施有机肥后提高了土壤的持水保肥能力有关,说明有机肥与化肥合理配合施用可以降低氮素的淋溶损失。

Forms and Amounts of Nitrogen in Leachates Affected by Different Fertilizations after one Wheat-maize Rotation

Nitrogen（N）leaching from soils results in low N use efficiency and environment deterioration.Lysimeters was constructed at the south edge of the Loess Plateau locating in the Guanzhong Plain,Shaanxi,China to evaluate the forms and amounts of nitrogen in the leachates under fertilizations during a wheat-maize rotation between 2007 and 2008.The fertilization treatments were（1）no fertilizer as the control,（2）inorganic N and phosphorus（P）fertilizers（NP）,and（3）NP ＋ organic manure（NPM）.Nitrogen amounts leached from the soil during the wheat-maize rotation were greater as the NO3--N form,next as the dissolved organic nitrogen（DON）,and lowest as the NH4＋-N.The ratios of NO3--N,DON and NH4＋-N to the total N（NO3--N,NH4＋-N plus DON）leached were 72.1%,26.2% and 1.7%,respectively.These results indicated that DON was also an important N source for potential use by plants.Furthermore,the amounts of leached NO3--N,DON and NH4＋-N were significantly higher in the NP fertilization than in the non-fertilizer control.In contrast,compared to the NP treatment during the wheat-maize growth period,the amounts of leached NO3--N,DON and NH4＋-N were significantly decreased by 64.4%,42.9% and 54.8% re-spectively at the 100 cm soil depth in the NPM fertilization.Our results indicated that such decreased N loss from leachates as a result of the application of inorganic fertilizer with organic manure could potentially mitigate NO3--N release to the environment and also enhance N use efficiency by plants.