不同施肥处理对连续三季作物氮肥利用率及其分配与去向的影响

采用室外盆栽试验系统研究了不同施肥处理对连续3个生长季作物生长状况、标记^15N利用率及其分配与去向的影响。结果表明，高量氮肥的施用能显著提高作物的生长和产量，而化肥配施玉米秸秆在第1生长季表现为抑制，第2、第3生长季则相反。作物体内来自标记氮肥的含量和比例随生长季的增加显著下降，高量氮肥和玉米秸秆的施用能显著提高其含量和比例（P〈0.05）。标记氮肥在土壤中的残留率随作物生长季的增加而降低，而标记氮肥的累积作物利用率和总损失率随着生长季的增加而增加，经过连续3季作物的吸收利用，标记氮肥在土壤中的残留率、累积作物利用率和总损失率分别平均为15．82％、61．11％和23．07％。标记氮肥的作物利用率和损失率主要发生在第1生长季内，高量氮肥的施用降低了标记肥料氮在土壤中的残留率，增加了氮素损失率；与单施化肥处理相比，化肥配施玉米秸秆能明显增加标记肥料氮在土壤和作物中的回收率，降低氮素损失率，提高比例为21．74％，从而说明在施肥当季，通过施入高C/N比有机物料玉米秸秆合理调节土壤中C源和N素营养的施用比例，可以达到增加氮肥在土壤中的残留率，提高氮肥利用率的目的。

Effect of N-fertilization on the Use Efficiency, Distribution and Fate of Labeled ^15N Fertilizer in Soil-plant Systems Over Three Continuous Crop Cultivations

A labeled ^15N fertilizer pot experiment was conducted to study the effect of single application of chemical fertilizer, and combination of chemical fertilizer and maize straw on the plant growth, ^15N use efficiency, distribution and fate of labeled ^15N fertilizer. The results showed that high application rate of labeled ^15N fertilizer significantly elevated the growth and yield of crop, however, the combination of chemical fertilizer and maize straw behaved restrain at the first crop cultivation, and accelerated at the second and third crop cultivations. The content and distribution proportion of plant ^15N obviously decreased with increase of crop cultivations, high application rate of labeled ^15N fertilizer and maize straw addition remarkably enhanced the content and distribution proportion of plant ^15N （P〈0.05）. The residual rate of labeled ^15N in soil decreased gradually with increase of crop cultivations, however, the accumulative N use efficiency of crops and overall loss rate of labeled ^15N increased with increase of crop cultivations. After absorption of crops in three continuous crop cultivations, its soil residual rate, accumulative N use efficiency of crop and overall loss rate of labeled ^15N was averagely 15.82%, 61.11% and 23.07% at maturity stage of the third crop cultivation, respectively. The use and loss of labeled ^15N fertilizer occurred at the first crop cultivation. In single chemical fertilizer treatments, high application rate of N fertilizer decreased residual rate of labeled ^15N in soil and increased its loss rate, combination application of chemical fertilizer and maize straw could obviously increase the N recovery rate by soil and plant, and decrease the loss rate of fertilizer N by 21.74%, which suggested that reasonable accommodating the application proportion of carbon source and nitrogen nutrition in soilby application of organic material（maize straw ） could increase residual rate of chemical N fertilizer in soil and advance N use efficiency of crop.