【作者】 吴永成；

【导师】 王志敏； 周顺利；

【作者基本信息】 中国农业大学 ， 作物栽培学与耕作学， 2005， 博士

【摘要】 本研究将华北地区冬小麦-夏玉米一年两熟作为统一的生产系统,综合考虑作物的持续高产和水肥资源的周年高效利用,田间试验和土柱模拟试验相结合,通过设置夏玉米不同氮肥用量及后茬小麦不同灌水量与施氮量处理,以及利用¹⁵N标记技术,系统研究了冬小麦-夏玉米种植体系土壤无机氮的时空动态、节水栽培小麦植株氮素积累分配与运转特点和节水栽培小麦对前茬深层土壤残留氮素的再利用能力,以揭示、阐明冬小麦-夏玉米种植体系节水省肥栽培小麦的氮素利用特征和夏玉米季施用氮肥在土壤中的运移残留及其后茬节水栽培小麦对深层土壤残留氮素的再利用机制。主要结论如下: 1.夏玉米根系分布浅,生育期内高温多雨,土壤供氮强度大,当季施用的肥料氮随雨水发生淋溶下移,有相当一部分氮素淋出玉米根区,并主要以硝态氮形式残留在下层（120～200cm）土壤中,氮肥利用率低。土柱模拟和大田试验均表明,夏玉米根系最大分布深度约为120cm,在平水年份（玉米季降水381mm左右）大田土壤硝态氮含量在夏玉米生育期内呈“N”型变化趋势,夏玉米施氮量90～360kgN╱hm²时,成熟期根区以下土体（120～200cm）土壤硝态氮残留量比不施氮处理多50.4～167.2kg NO₃-N/hm²。土柱模拟条件下夏玉米¹⁵N标记肥料氮在水分作用下也明显向土壤深层移动,1m以下土壤残留¹⁵N量占2m土体内¹⁵N总残留量的18.28%。大田夏玉米当季氮肥表观利用率平均约为11.0%。 2.冬小麦根系分布深,节水栽培明显提高根群中下层根系的比例,能够高效回收利用前茬玉米季深层土壤残留氮素,减少了氮素损失。冬小麦根深可达2.0m,春浇1～2水条件下1m以下土体根系占总根系的比例约为春浇4水的2倍。土柱春浇1水处理冬小麦能够吸收利用前茬玉米残留在2m土体各土层的¹⁵N标记肥料氮,对2m土体残留¹⁵N的总回收率为14.35%,对各土层残留¹⁵N的回收率处于22.98%～4.41%范围。大田春季不浇水和春浇2水条件下,冬小麦对于100～200cm深层土壤放置的¹⁵N标记氮肥均能吸收利用。原状土柱深层土壤¹⁵N标记氮肥试验进一步验证了节水栽培小麦对下层土壤氮素的再利用能力,并表明植株对100～110cm、120～130cm、140～150cm各层土壤标记¹⁵N的回收率（%）分别为16.26%、7.33%和4.38%。冬小麦节水省肥栽培,对前茬玉米下层（120～200cm）土壤残留硝态氮的利用量约为17.02kgN/hm²,约占小麦吸氮量的8.61%。 3.小麦节水省肥栽培可促进植株营养器官氮素的有效转运输出,明显提高氮素生理效率和水分利用效率,实现了高产和水肥资源高效利用的统一。（1） 限肥条件下,节水栽培小麦（春浇1～2水）相对增加了开花前植株吸氮比例,并提高了开花后植株氮素的转运率（%）、转运量及其对籽粒的贡献率（%）;其氮素生理效率（平均≥42kg╱kgN）明显高于春灌4水处理（平均≤38kg/kgN）。相关分析表明,小麦灌水量与氮素生理效率之间呈抛物线曲线关系,生育期内灌水量≤1500m³/hm²时氮素生理效率变化较小,灌水量>1500m³/hm²,则氮素生理效率会发生明显的下降;小麦灌水量与氮素收获指数之间则呈线性负相关。产量和水分利用效率随灌水量增加也呈抛物线型曲线变化。（2） 限水条件下,小麦一次性基施氮157.5kgN╱hm²氮素生理效率高达43.38～44.15kg╱kgN,在此基础上增施氮肥或把部分氮肥用于拔节追肥均导致氮素生理效率的下降。相关分析表明,限水条件下小麦施氮量与开花后植株氮素的转运率（%）及氮素转运对籽粒的贡献率（%）呈线性负相关;与氮素生理效更多还原

【Abstract】 Application of nitrogen fertilizer is one of the most important measures for increasing crop yield in agriculture. However, misuse of nitrogen fertilizer （particularly overuse） in traditional winter wheat-summer maize production system in northern china was frequent, which caused low nitrogen fertilizer use efficiency and related environmental problems （for example NO3"-N leaching to groundwater）. In order to improve agricultural resources （water and nitrogen fertilizer） use efficiency and crop yield simultaneously, field and undisturbed soil column experiments were carried out at Wuqiao Experiment Station of China Agricultural University in Hebei Province from 2002 to 2004. The objects of this study are: （1） investigating dynamics, spatial distribution and accumulation of soil NO₃^--N in the summer maize-winter wheat production system, （2）examining plant nitrogen accumulation, distribution and use efficiency under different nitrogen fertilizer applied rates and irrigations in waiter wheat season., and （3）testing the ability of winter wheat to capture and re-use subsoil ¹5N-labeled fertilizer nitrogen under water-saving cultivation in the condition of field or soil column. The results are as follows.1. There was leaching of nitrogen fertilizer applied in summer maize season influenced by rainwater, and a part of nitrogen fertilizer has been leached out of maize root zone and accumulated in subsoil （120²00cm ） in the form of residual NO3-N because of these factors such as shallow roots, much rainfall and great ability of soil nitrogen provision . Residual soil NO3-N in 2m soil profile increased with more nitrogen applied, and the treatments of nitrogen applied （N90,N180,N270,N360） increased the residual soil NO3-N content in the 120²00cm soil profile by 50.4 150.4kg NO3-N/hm2 compared to non-nitrogen applied treatment （NO） at harvest stage. The soil column results indicated that fertilizer ¹5N distinctively move to deep soil layer （below soil depth 100cm） and some ¹5N fertilizer nitrogen leaching out of summer maize roots zone under the condition of ¹5N-labeled Urea applied. The proportion was amount to 18.28% of 1.0².0 m soil profile residual ¹5N in whole 2.0m soil profile. It was suggested that in summer maize season some nitrogen was leached out of root zone, and could not be absorbed, which not only reduced nitrogen fertilizer use efficiency, but also might cause ground water pollution.2. The residual ¹5N-labeIed fertilizer nitrogen of 2m soil profile from summer maize season could be captured and re-used by winter wheat under water-saving cultivation due to the significant difference of roots spatial distribution between winter wheat and summer maize. There are distinctively difference of rooting depth or roots strap spatial distribution between summer maize and winter wheat whether in the field or in the column conditions. The most root depth was about 120cm for summer maize and exceeded 2.0m for winter wheat at anthesis stage. Compared with traditional cultivation （w4 treatment） in winter wheat, water-saving cultivation （wO or w2 treatment） significantly increased the percentage of root dry weight at deep subsoil, which could explain why ¹5N-labeled nitrogen placed in deep subsoil could be captured under w2 treatment or wO treatment condition in the field condition. In the undisturbed soil column, wheat could also capture ¹5N-labeled nitrogen in deep soil. Recovery rates of ¹5N-labeled nitrogen in 100¹10cm,120¹30cm,and 140 150cm soil layers were 16.26%,7.33% and 4.38% respectively. Winter wheat growth in soil column could capture and re-use the residual fertilizer ¹5N in whole 2.0m soil profile from front stubble summer maize under the treatment of one-time irrigation in spring. The range of residual fertilizer ¹5N recovery rate （%） by winter wheat absorbed is 22.98% 4.41% and more lower with depth increase. Compared withconventional irrigation treatment （W4N 157.5 ） , water-saving and fertilizer-saving cultivation （W2N157.5） Significantly decreased subsoil NO3-N content in field winter更多还原