用15N标记肥料研究旱地冬小麦氮肥利用率与去向

在黄土旱塬 2年的田间试验表明 ,在特殊干旱年里小麦施氮肥增产仍很显著 ,但氮肥效果受到明显抑制 ,施氮处理间小麦产量差异不显著。播种前土壤水分含量对旱作小麦产量有决定性作用。15N微区试验表明 ,尿素作基肥混施入耕层后 ,小麦当年利用率为 3 6 6%～ 3 8 4% ,土壤残留率为 2 9 2 %～ 3 3 6%。氮肥的后效显示 ,土壤残留的氮素可被第 2茬小麦部分利用 ,占施氮量的 2 1 %～ 2 8% ,相当于 0～ 40cm土壤残留氮的 6 7%～ 8 7%。土壤残留的氮素主要集中在 0～ 40cm土层中 ,土壤剖面中残留氮随土壤深度增加而减少。膜间种植对小麦产量、氮肥利用率在试验年里没有显示作用 ,但大大增加了氮肥在土壤中的残留率。

STUDY ON NITROGEN EFFICIENCIES OF DRY LAND WHEAT BY ~(15) N LABELED FERTILIZER

A wheat field experiment was conducted on Heilu soil in the south of Loess Plateau, Changwu county, Shanxi Province. Efficiency of nitrogen fertilizer was studied by using 15 N labeled fertilizer.The results showed that the effect of yield increasing was obvious but not eventual diferences among N treatments in special drought years were found. Wheat yield depend greatly on soil water before sowing. 15 N study showed that plant recoveries were in the range of 36 6%～38 4%; N remained in 0～40cm soil ranged in 29 2%～33 6%. Remained N may be partly used by second crop in 2 1%～2 8% of applied N or in 6 7%～8 7% of 0～40 remained N, remained N in soil profile decreased greatly with increase of soil depth. Mulching and ridge planting had no effect on crop yield and NUE but increased the rate of remained N.