【作者】 李云；

【导师】 高亚军； 李世清； 王朝辉；

【作者基本信息】 西北农林科技大学 ， 植物营养学， 2006， 硕士

【摘要】 氮肥在世界粮食生产中具有重要的作用,我国从1994年以后氮肥每年使用量均在2×107t以上,大量施用氮肥的结果导致越来越多的矿质氮素残留在农田土壤,既不利于氮肥利用率的提高,而且产生许多环境问题。本文通过三个田间试验,分别研究旱地不同栽培条件对氮素的残留及其吸收利用的影响、土壤剖面残留氮对作物的有效性和不同作物种类及种植方式对土壤残留氮素利用能力的影响,旨在查明影响旱地氮素残留、吸收和再利用的因素,从而为旱地养分管理提供科学依据。得出的主要结论有:(1)地膜覆盖和垄沟种植是旱地实现冬小麦高产的重要栽培模式,然而,地膜覆盖和垄沟种植土壤中残留的硝态氮也显著提高,因此,需要将土壤培肥、增加有机物输入与这两种模式结合起来。(2)秸秆覆盖处理和常规模式处理前2年的小麦产量和吸氮量均无显著差异,而第3年秸秆覆盖的均明显高于常规模式,表明冬小麦田秸秆覆盖的增产效果需要若干年的积累。(3)施氮高达240 kg/hm2时小麦产量和吸氮量显著高于施氮120 kg/hm2,然而,施氮土壤剖面残留的硝态氮也显著增加。当地高产低氮残留的适宜施氮量应在120和240 kg/hm2之间。(4)种植密度增加显著提高小麦产量、养分吸收量和氮肥利用率,土壤较深层累积的硝态氮则有降低的趋势,表明适当提高小麦种植密度是旱地高产高效栽培的一条重要途径。(5)连续施肥几年后,0~200 cm土壤剖面中残留矿质氮与小麦的总吸氮量相当。可见,土壤残留的矿质氮数量十分可观。(6)随着土壤中残留氮量的增加,其被作物的再吸收量有增加的趋势,而无效损失量同样增加,深层氮损失的机会也增加。(7)苜蓿比小麦更能利用较深土壤的残留氮,但不论是小麦还是苜蓿,浅层土壤残留氮均是作物氮素的主要贡献者。(8)大豆和小白菜与玉米间作时对土壤残留氮素的再利用能力比两者单作时强,而且间作时土壤氮素的消耗和损失主要发生在浅层,单作时则有相当一部分氮素的损失发生在深层土壤。更多还原

【Abstract】 Nitrogen fertilizer has important role on food production in world. More than 2×107t of N fertilizer has been applied every year in China since 1994. Excessive N fertilizer applied leads to more residual N in soils of farmland. It not only reduces N fertilizer utilization efficiency, but also causes many environmental problems. Three field experiments were conducted to investigate the effect of different cultivation methods on residual N and N uptake, availability of residual N for next crops and the effect of different crops and different cropping patterns on utilization of residual N in dryland. The main conclusions include:(1) Plastic film mulching and furrow planting increased wheat yield, N uptake by wheat and N fertilizer utilization efficiency, compared to no mulch, indicating that both of them were important to reach the good harvest. However, they also increased the accumulation of NO3--N in soil because of the accelerated mineralization of organic N under higher soil temperature and water content, suggesting it was necessary to increase organic material input along with these two cultivation methods.(2) There were no significant differences of wheat yield and N uptake by wheat for the first two years between straw mulching and no mulch, while they had significant differences for the third year, indicating that it needed some years to see the effect of straw mulching on crop yield.(3) Wheat yield, N uptake by wheat and residual nitrate N throughout the profile of 0~200 cm were significantly higher when 240 kg N/hm2 was applied than 120 kg N/hm2. N rate of 120~240 kg/hm2 was reconmened for the winter wheat growth in the local region in order to reach the goal of high yeild and low residual N content in soil.(4) Wheat yield, N uptake by wheat and N fertilizer utilization efficiency increased significantly with the increase of wheat density, while residual nitrate N showed a reduction in the deeper layer of soil, suggesting that the appropriate increase of wheat density was a way to obtain high production and high efficiency.(5) After 3 years cropping, 446 kg/hm2(292~686 kg/hm2 )of residual mineral N (NH4+-N+NO3--N) were found in 0~200 cm depth of soil, which were equivalent to更多还原