高肥力土壤冬小麦/夏玉米轮作体系中化肥氮去向研究

冬小麦 夏玉米轮作是华北平原主要的耕作方式之一。本研究通过田间15N微区试验 ,研究了高肥力土壤条件下冬小麦 夏玉米轮作体系中化肥氮的去向。结果表明 ,在每季施氮量 1 2 0～ 3 60kg hm2 条件下 ,冬小麦对化肥氮的吸收率为 2 3 8%～44 5 % ,夏玉米为 2 6 5 %～ 5 1 1 % ,整个轮作周期为 2 8 0 %～ 5 1 6%。而后茬作物对化肥氮的吸收量较少 ,低于施氮量的 1 0 %。当季化肥氮的土壤残留率约占施氮的2 0 %～ 5 0 % ,轮作周期化肥氮的土壤残留率约占施氮的 3 0 %。当季和轮作周期化肥氮的损失量和损失率 ,均随着施氮量的提高而显著升高。当施氮量分别为 2 40kg hm2和 72 0kg hm2 时 ,整个轮作周期化肥氮的损失率分别为 1 9 0 %和 40 5 %。

FATE OF FERTILIZER N IN WINTER WHEAT/SUMMER MAIZE ROTATION SYSTEM ON HIGH-ERTILITY SOIL

A field trial with 15 N\|microplots was conducted to study the fate of fertilizer N on high\|fertility soil for winter wheat/summer maize rotation system,one of main cropping systems at North China.The results showed that when 120～360kg/hm\+2 of nitrogen applied,the recovery of fertilizer nitrogen were 23\^0%～44\^5% for winter wheat,26\^0%～51\^1% for summer maize and 28\^0%～51\^6% for one winter wheat/summer maize rotation,while less than 10% of fertilizer nitrogen taken up by the next crop.The soil residual nitrogen from fertilizer was in 30%～50% for current crop season and about 30% at the end of one winter wheat/summer maize rotation.While the loss of fertilizer nitrogen,regardless in amount or in % of nitrogen applied,increased with the N applied rate.For the whole rotation system,the cumulative loss of fertilizer nitrogen was only 18\^98% at nitrogen applied rate of 240kg/hm\+2 while 40\^50% at nitrogen applied rate of 720kg/hm\+2.There was not significant difference in soil N uptake by crops between low N applied rate treatments,but with the increase of N applied rate N uptake by crops got lower,indicating that so\|called “negative added nitrogen interaction” occurred.