【作者】 苏涛；

【导师】 王朝辉；

【作者基本信息】 西北农林科技大学 ， 植物营养学， 2004， 硕士

【摘要】 施用氮肥是提高作物产量的重要手段。然而，越来越多的氮肥投入不可避免地导致大量未被作物吸收利用的矿质氮素残留在农田土壤，进而污染地表、地下水体和大气等生态环境。本文首先采用不同类型的土样， 研究了影响土壤矿质氮测定值的因素，确定了合理的土壤矿质氮测定方法。然后通过田间试验，分别种植冬小麦和夏玉米，研究了作物生长时期旱地土壤残留矿质氮的动态变化及其影响因素。得出的主要结论有：1.土样预处理方式、过筛孔径大小、液土比、振荡时间和浸提液保存方式都不同程度影响土壤矿质氮的测定结果。采用新鲜土样直接测定、过筛孔径3mm、液土比10：1、振荡时间60min、浸提液不经保存直接用连续流动分析仪测定效果较好。2.冬小麦生长季节0-200cm土层的矿质氮残留量相当可观，且从播种到拔节期呈增加趋势，并在拔节期达最高值，为224.5kg.hm-2，主要分布在100cm以下的土层。此后，土壤铵态氮数量迅速增加，并高于硝态氮。土壤剖面中矿质氮残留累积峰值随生长期后移亦有向下层移动的趋势，尤以铵态氮的移动最为明显。到冬小麦收获时，铵态氮残留累积峰值已达到180－200cm土层，该层的铵态氮数量达29.6kg.hm-2。3.种植小麦可明显降低整个0-200cm各土层的硝态氮残留量，而对铵态氮及其剖面分布只有到小麦收获才出现显著影响；冬小麦生长后期，土壤温度和大气温度与土壤铵态氮有一致的动态变化趋势，两者呈明显的正相关关系；土壤含水量与土壤铵、硝态氮动态变化无确定关系；少量的降水量，也很难以导致土壤硝态氮的下渗。4.夏玉米生长季节0-200cm土层矿质氮残留量最多时达到861.8kg.hm-2，且土壤硝态氮数量明显大于同期的铵态氮。随着生育期的后移，土层剖面中的矿质氮素有向土壤深层迁移的明显趋势，尤其是土壤硝态氮。到玉米收获时，土壤硝态氮的残留峰值已下移到200cm土层以下。5.种植玉米可明显降低土壤硝态氮残留量，对铵态氮及其剖面分布却无明显影响；施用氮肥可明显增加土壤硝态氮残留数量，并影响其剖面分布；土壤温度和大气温度的升降与土壤铵态氮的高低动态变化相一致，与硝态氮的变化呈相反趋势；土壤铵态氮和硝态氮的数量随土壤含水量升降而增减，但在时间上有程度不一的滞后现象；在降水量大而集中的北方夏季，旱地土壤的硝态氮会被淋移到200cm以下的土层。更多还原

【Abstract】 Application of N fertilizer is an important measure in increasing crop yield. However, more and more input of N fertilizer has unavoidably led to a great deal of mineral N residual in cropland soils due to the low recovery of fertilizer N by crops, which subsequently has caused serious pollution of ground and underground water, and atmosphere, as well as the other ecological environment. In this thesis, factors affecting determination of soil mineral N were studied using different kinds of soils, and the optimum determination method was designed. Then, field experiments were carried out, using winter wheat and summer maize as test crops, to study the dynamics of residual N in dryland soils and its affecting factors during the crops growing season over years. The main conclusions are as follows:1. The determination of soil mineral N was affected by the method of soil sample processing, diameter of sieve, ratio of extract solution to soil, vibration time and storage method of the soil extract to different degrees. The optimum method to determine the soil mineral N is using fresh soil sample, adopting 3 mm sieve, 10:1 extract solution to soil ratio, and 60 min of vibration time, and determining the mineral N in soil extract right after extraction by Continuous Flow Analyzer.2. A great deal of residual mineral N was found during the growing season of winter wheat, and the amount of residual mineral N was increased after seeding with the maximum value being reached at jointing stage and the most of the residual N in soil layers bellow 100 cm. After the stage of jointing, the amount of soil ammonium-N increased rapidly, and even became higher than nitrate-N in soil. The accumulation peak of mineral N in soil profile was found to move down to deep layers with the extension of growth stages, especially the soil ammonium-N. At harvest of winter wheat, the accumulation peak of ammonium-N had already moved down to the 180-200 cm soil layer, with the amount of 29.6 kg N hm-2. 3. The amount of nitrate-N residue in 0-200 cm soil layer was obviously decreased by growing winter wheat, but the amount of ammonium-N and its distribution in soil profile was not significantly affected until harvest of winter wheat. The amount of soil ammonium-N was observed to positively change with the change of temperature of soil and air. No certain relationship was found between changes of the amount of soil ammonium-N or nitrate-N and the soil moisture content, and soil nitrate-N was hardly leached down to deep soil layer by the lower amount of precipitation during the late growing season of winter wheat.4. The amount of mineral N residual in 0-200 cm soil layer was as high as 861.8kg hm-2 during the growth season of summer maize, and the amount of soil nitrate-N is obviously higher than that of ammonium-N at the same stage. With the prolongation of growing season, <WP=7>mineral N in soil profile showed obvious trend of moving down to deep soil layers, especially soil nitrate-N. The accumulation peak of soil nitrate-N had moved down to soil layers bellow 200 cm under soil surface.5. The amount of residual nitrate-N was obviously decreased by growing summer maize, while the amount of ammonium-N and its distribution in soil profile was not affected. Application of N fertilizer significantly increased the amount of residual nitrate-N, and affected its distribution in the soil profile. The amount of soil ammonium-N was observed to positively change with the change of temperature of soil and air, and nitrate-N negatively changed with the temperature. However, the change of the amounts of soil ammonium-N and nitrate-N was consistent with that of soil moisture, although the former was changed slower in time than the former in different degrees. In northern China, soil nitrate-N was able to be leached down to soil layers bellow 200 cm under soil surface by the heavy rainfall during the summer season.更多还原