长期不同施肥对小麦-玉米轮作体系土壤残留肥料氮去向的影响

【目的】研究残留肥料氮在不同肥力土壤中的去向。【方法】采用15N标记田间微区试验法研究小麦-玉米轮作下，施用的肥料氮在3种长期（19年）不同施肥处理土壤（不施肥土壤，No-F；施用氮、磷、钾化肥土壤，NPK；有机无机配施土壤，MNPK）连续3季作物收获后的去向。【结果】NPK和MNPK处理土壤3季作物对标记氮肥总利用率分别为57%和65%，均显著高于No-F处理土壤（28%）（P＜0.05）。No-F、NPK和MNPK处理土壤随后两季（第二季和第三季）作物对第一季收获后残留氮肥的利用率分别为17%、15%和8%，其中No-F处理土壤第三季作物对残留肥料氮的利用率为7%，显著高于NPK（2%）和MNPK处理（3%）。3季作物收获后，No-F、NPK和MNPK处理土壤施入氮肥在土壤和作物系统的总回收率分别为50%、77%和84%，损失率分别为50%、23%和16%。3季作物收获后三供试土壤标记氮肥残留率均约为20%，且主要分布在0—20 cm土层。【结论】长期平衡施肥尤其长期有机无机配施可显著提高肥料氮利用率，降低氮肥损失。

Effects of Long-Term Different Fertilizations on the Fate of Residual Fertilizer N in a Wheat-Maize Rotation System

【Objective】The fate of residual fertilizer N was studied in soils with different fertilities. 【Method】The aim of this experiment was to study the fates of residual fertilizer N after three consecutive growing seasons in the soils with a history of long-term different fertilizations (including no fertilizer (No-F soil), inorganic NPK fertilizer (NPK soil), and cattle manure plus inorganic NPK (MNPK soil)) using the 15N microplot method. 【Result】The total urea-15N use efficiency in the NPK and MNPK soils (57% and 65%, respectively) during the three growing seasons was significantly (P＜0.05) higher than that in the No-F soil (28%). The uptake rate of the residual urea-15N by the crops growing in the subsequent two seasons were 17% for the No-F soil, 15% for the NPK soil, and 8% for the MNPK soil. And 7% of the residual urea-15N was taken up by the third crops in the No-F soil, 2% in the NPK soil and 3% in the MNPK soil. The total urea-15N recovery rate (urea-15N uptake by the three crops and urea-15N residual in the 0-100 cm soil layers) were 50% in the No-F soil, 77% in the NPK soil and 84% in the MNPK soil. And the total loss rate of urea-15N were 50% in the No-F soil, 23% in the NPK soil and 16% in the MNPK soil after the three growing seasons. The residual rate of the urea-15N in the 0-100 cm soil layers was about 20% in all soils after the three growing season, mainly in the 0-20 cm soil layers.【Conclusion】 The conclusion is that the residual fertilizer N has high availability for the subsequent crops, and the long-term combined application of cattle manure and inorganic NPK can increase fertilizer N use efficiency and decrease its loss.