潮褐土冬小麦-夏玉米轮作体系氮肥后效及去向研究

【目的】在华北平原地区，研究肥料氮在两个轮作季四茬作物中的后效和去向。【方法】采用田间微区15N示踪试验，前茬设置5个氮素水平：0、75、150、225、300 kgN•hm-2（表示为N0、N75、N150、N225、N300），副处理为小麦品种：科农9204和河农822，共计10个处理。【结果】在该试验条件下，后三茬作物均能吸收利用第一茬冬小麦残留在土壤中的15N标记肥料。第二茬夏玉米、第三茬冬小麦和第四茬夏玉米对残留15N的利用率分别为6.5%-14.1%、0.9%-2.9%和1.2%-1.6%。四茬作物的叠加利用率显著高于氮肥当季利用率，N75、N150、N225和N300处理叠加利用率分别是53.8%、58.7%、58.6%和55.8%（第一茬为河农822小麦品种）；60.0%、61.3%、60.9%和55.2%（第一茬为科农9204小麦品种）。经过四季作物种植后，土壤剖面中仍有22.3-96.2 kgN•hm-2的氮素残留，残留率为22.1%-32.8%，累积总损失量可达9.3-55.3 kgN•hm-2，损失率为8.9%-18.6%。【结论】在小麦当季，高施氮量条件下肥料主要残留在土壤中，后茬作物可以吸收土壤残留氮肥。土壤中15N含量随施氮量的增加而增加，随着茬口的增多有垂直向下运移的趋势，第一茬作物品种间无显著差异。

Fate and Residual Effect of Fertilizer Nitrogen Under Winter Wheat-Summer Maize Rotation in North China Plain in Meadow Cinnamon Soils

【Objective】The fate and residual effect of fertilizer nitrogen under winter wheat-summer maize rotation were studied using filed 15N microplot in north China.【Method】In the field 15N-micropolt experiments,nitrogen applied at 0,75,150,225,300 kgN.hm-2(N0,N75,N150,N225,N300) and two wheat varieties were used under winter wheat-summer maize rotation in North China Plain.【Result】The results showed that all the late three crops could utilize the15N-labeled residual from the first winter wheat.Along with15N-labeled fertilizer application rates increasing,the15N was up-taken by the after three crops increased significantly,but following the increasing of crops for rotation,the absorption amounts and absorption rate decreased significantly.Overlying N utilization efficiency of four crops was significantly higher than the N utilization efficiency of the right winter wheat.The overlying N utilization efficiency in N75,N150,N225 and N300 treatments accounted for 53.8%,58.7%,58.6% and 55.8% when HN822 was the first crop and 60.0%,61.3%,60.9% and 55.2%,respectively,when KN9204 was the first crop.After the fourth summer maize harvest,the range of soil residue in profile was 22.3-96.2 kgN.hm-2,the ratio of soil residue was from 22.1% to 32.8%.The range of total loss was 9.3-55.3 kgN.hm-2,and the loss ratio was 8.9% to 18.6%.【Conclusion】Two rotation systems finished.There was residual15N in 0-200 cm soil profile after two crops rotation.With the nitrogen fertilizer application rates increasing,the nitrate and residual15N amount increased.With the increasing of crops growth,the moving trend of nitrate and residual15N was downward in vertical direction.