黄泛区潮土-冬小麦系统中尿素的转化和化肥氮去向

THE TRANSFORMATION OF UREA AND THE FATE OF FERTILIZER NITROGEN IN FLUVO-AQUIC SOIL-WINTER WHEAT SYSTEM IN FLOODED PLAIN OF HUANGHE RIVER

在田间条件下,用^(15)N标记的微区试验法研究了潮土-冬小麦系统中尿素的转化和化肥氮的去向。结果表明:土壤中尿素水解后,主要进行硝化和生物固定,而被粘土矿物固定的量很少;小麦返青后,随着气温上升,生物固定的标记氮不断分解,其量可达总生物固定量的60％。作为基肥条施的尿素,其损失略高于作返青肥或拔节肥表施后随即灌水的处理。氮素损失主要发生在春季气温回升后的生长期间,当季的淋洗损失极微。在较为适宜的用量和施用技术下,化肥氮的损失仍达33—45％,其中以碳酸氢铵为最高,次为硫酸铵和硝酸铵,而尿素和硝酸铵中的硝态氮损失最低。

The transformation of urea and the fate of fertilizer-N in fluvo-aquic soil-winter wheat system in the semi-humid warm temperate zone of China were investigated in the field by micro-plot technique with 15N. Theresults show.1.Nitrification and immobilization are dominant processes in soil of urea-N banded as basal fertilizer.The remineralization of the immobilized N in spring is as high as around 60%. Only a few percent of the N applied is fixed by clay minerals of the soil, though the dominant clay minerals of the soil are hydromica and montmorillonite.2.The loss of urea-N banded as basal fertilizer is higher than that of top-dressed at revival or enlongation stages in spring. Irrigation just after top-dressing lowers the loss of urea-N. N loss is taking place only inspring when the temperature rises. Leaching loss is negligible in the growing season of wheat.3.Losses of fertilizer-N are in the range of 33-45%,among which am-monium bicarbonate is the highest, followed by ammonium sulfate and 15NH4NO3 while the losses of urea and NH415NO3 are the lowest.