【摘要】 在黄土高原南部旱地有大量氮素残留背景的田块上,研究了不同氮肥用量对夏玉米生长及对土壤水分、硝态氮、铵态氮累积及其剖面分布的影响。结果表明适量施氮可以提高作物产量;过量施氮没有表现出增产效果,其氮肥利用率只有3.9%,残留率则高达87.2%。施氮240kghm-2时,0~200cm土层土壤水分达到593mm,且可以下渗到200cm土层;不施氮和施氮120kghm-2小区土壤的蓄水量分别为561和553mm,可下渗到180cm。对矿质态氮而言,施氮量可以显著影响土壤中硝态氮的累积和分布,但对铵态氮的影响较小;施氮0,120,240kghm-2时,收获期土壤硝态氮累积量分别为78,148,290kghm-2,硝态氮的下移前沿分别到达60,60,140cm。可见,适量施氮会促进作物对土壤水氮的利用,提高作物生物量和产量;过量施氮导致硝态氮在土壤中大量累积,提高硝态氮随水分淋溶危险;但硝态氮向下层土壤的移动显著滞后于水分。更多还原

【Abstract】 A field experiment was carried out to study the effect of nitrogen (N) fertilizer rate (0, 120 kg N hm -2 , and 240 kg N hm -2 ) on summer maize (Zea mays L. var. Shaandan 911) and soil water-nitrogen dynamics. The dryland study was conducted in the southern part of the Loess Plateau during the warm and rainy summer of 2004 on a soil with high amounts of residual mineral N. The results showed that appropriate N application rates increased crop biomass and grain yield. Over application of N fertilizer did not increase crop biomass or yield. In the over-fertilized plots, N use efficiency was only 3.9% and N residual efficiency was as high as 87.2%. Water distribution in the soil profile was significantly influenced by the N rate. The 240 kg N hm -2 treatment contained 593 mm of water at harvest and the water had moved to a depth of 200 cm. In comparison, the 0 kg N hm -2 treatment contained 561 mm of water and the 120 kg N hm -2 contained 553 mm of water. In both treatments, water had moved to a depth of 180 cm. Nitrogen rates significantly affected the accumulation and distribution of nitrate N in the soil profile, but had no significant effect on the amount or distribution of ammonium in the soil profile. At harvest, total nitrate N in the 0-200cm depth was 78 kg hm -2 in the 0 kg N hm -2 treatment compared to 148 kg hm -2 in the 120 kg hm -2 and 290kg hm -2 in the 240 kg hm -2 . Nitrate N had moved down to a depth of 60 cm in the 0 and 120 kg hm -2 treatments and 140cm in the 240 kg hm -2 treatment due to percolation during the summer rainfall. The results suggest that appropriate N application rates could promote the utilization of soil water and mineral N by summer maize and increase its biomass and grain yield. In contrast, over application of N results in the accumulation of a large amount of nitrate N in the soil profile and increases the risk of nitrate N leaching to the subsoil. In addition, it was observed that nitrate N leaching is significantly slower than the downward movement of soil water.更多还原