【作者】 高明霞；

【导师】 胡田田；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2004， 硕士

【摘要】 本文以玉米作为试验材料，研究了塿土、砂土的玉米根际土壤NO3--N在常规灌水、交替灌水和固定灌水这三种灌水方式下的分布状况，还进一步研究了在不同施氮量、不同施磷量下其分布的影响。得到以下结论。1. 在常规灌水、交替灌水、固定灌水方式的湿润区，玉米根际土壤NO3--N的分布均呈累积趋势，且表现为交替灌水＞固定灌水＞常规灌水；而在干燥区，交替灌水与固定灌水显示出不同的分布状况，NO3--N的分布均呈现亏缺趋势：固定灌水＞交替灌水＞常规灌水，但在距根面2mm的范围内都存在着NO3--N的相对富集。根际下部的硝态氮含量大于根际上部的硝态氮含量。2. 在塿土中，增加施氮量，使根际土壤氮的浓度增加，增大了根际NO3--N的累积趋势，改变了交替灌水方式干燥区根际硝态氮的分布趋势，由亏缺趋势变为累积趋势。固定灌水方式下硝态氮分布在湿润和干燥区的累积和亏缺趋势分别得到加强。3.施磷有助于作物对硝态氮的吸收，能提高作物在受到水分胁迫时对硝态氮的吸收，增强了硝态氮在低含水量土壤中向根面迁移的扩散作用。4.低氮条件下，砂土根际硝态氮的分布在不同灌水方式下均较平缓，但固定灌水与交替灌水处理的干燥区具有轻微的亏缺趋势，且亏缺趋势基本一致，近根处有轻微的累积趋势，交替灌水大于固定灌水，湿润区硝态氮的累积趋势小于干燥区。高氮条件下，根际硝态氮的累积或亏缺趋势逐渐明显。固定灌水的干燥区根际硝态氮的分布呈累积与亏缺并存的现象，近根处有明显的累积趋势，其余处理均呈明显的累积趋势。这说明植物根系依靠根水倒流在水分含量较少的干燥区也能继续吸收硝态氮，在高氮条件下干燥区质流作用与扩散作用共同起作用。不同灌水方式下，质流作用与扩散作用的影响不同。5. 塿土玉米根际NO3--N含量均大于砂土。低氮条件下，不同灌水方式下，塿土根际硝态氮具有明显不同的分布趋势，砂土根际硝态氮的分布差异不大。高氮条件下，塿土根际硝态氮和砂土根际硝态氮的分布趋势差异不大。固定灌水的干燥区近根处的根际硝态氮累积范围，砂土较塿土宽。表明根水倒流对硝酸根在土壤中向根迁移所起的作用，在砂土中大于塿土。 本文的创新点 <WP=6>本文首次结合控制性交替灌溉这种新的节水灌溉方式，利用垂直根面法对根际硝态氮的分布进行了系统的研究。硝态氮在根际的分布呈亏缺与累积趋势并存现象，意味着硝态氮在根际从土体向根面的迁移存在着两种方式，即扩散作用和质流作用。作物在玉米干燥区仍能吸收硝态氮。近根处的硝态氮存在累积现象，且质地越砂，硝态氮的累积范围越宽，根际硝态氮累积与亏缺并存的现象越明显，说明在干燥区水分倒流对硝态氮吸收起着主要作用。灌水方式不同，玉米根际硝态氮的分布趋势不同。找到了交替灌溉有利于提高根系对硝态氮吸收的试验证据，为控制性交替灌溉技术提供了新的理论依据。更多还原

【Abstract】 In this paper, the distribution of NO3--N in maize rhizosphere was studied under normal irrigation, alternative irrigation and fixed irrigation by spliting root in loess soil and sandy soil, and the effects to the distribution were studied under different amount of N application and different amount of P application furthermore. Following results have been obtained. 1.The accumulation of NO3--N in maize rhizosphere is observed in the wet zone under different irrigation styles, and the accumulative tendency of NO3--N in rhizosphere are alternative irrigation＞fixed irrigation＞normal irrigation. On the contrary, the depletion of NO3--N in maize rhizosphere is observed in the dry zone under different irrigation styles, and the depletion tendency are fixed irrigation＞alternate irrigation＞normal irrigation, but NO3--N is relatively accumulated in the rhizosphere soil within 2mm to the surface of plant root. The content of NO3--N in the lower part of rhizosphere is higher than that in the upper part.2. With adding NO3--N amount, the content of NO3--N in rhizosphere increases, the accumulation tendency is expanded, and the distribution of NO3--N in the dry zone is changed from the depletion tendency to the accumulative tendency under alternative irrigation. The expansion of depletion tendency in the dry zone and that of accumulation tendency in the wet zone are expanded respectively.3. Increasing P application are beneficial to crop to uptake NO3--N, it can improve the performance of crop on NO3--N uptake under the stress of soil moisture. It means that the diffusion of NO3--N in rhizosphere to the root plane strengthened under lower water content.4. In sandy soil, under lower content of NO3--N, the distributions of NO3--N are almost smooth and even under different irrigation styles, but there are weak depletion tendencies of NO3--N in the dry zones and weak accumulative tendency in the dry zones near plant root under fixed irrigation and alternative irrigation, the accumulative tendency are alternative irrigation＞fixed irrigation. The accumulative tendency in the wet zones is less than that in the dry zones. Under higher content of NO3--N, the accumulative or depletion tendency became significant in the maize rhizosphere. The phenomena of accumulation and depletion of NO3--N exist in the dry zone under fixed <WP=8>irrigation at the same time, the accumulative tendency in the dry zones near plant root is apparent, the accumulative tendency are apparent under other irrigation styles. It shows that plant roots can uptake nutrients under the lower moisture content depending on water reverse flow in plant roots. The affection of mass flow and diffusion are different under different irrigation styles.5. The content of NO3--N in loess soil rhizosphere are higher than that of sandy soil. Under lower content of N, The distributions of NO3--N in loess soil rhizophere are different under different irrigation styles apparently, but there are little differences in sandy soil. Under higher content of N, there are little differences in the distributions of NO3--N between loess soil and sandy soil. The extent of the NO3--N accumulation in sandy soil rhizosphere is wider than that in loess soil under fixed irrigation. This shows that the role of water reverse flow in plant roots in sandy soil is greater than that in loess soil at NO3--N transference from soil to plant roots.The new finding was followed:In this paper, the distribution of NO3--N in the rhizosphere was studied systematically by the dense root plane in contract with soil blocks combined with a new way of saving irrigation style- controlled alternate irrigation for the first time.The phenomena of accumulation and depletion of NO3--N exist in the rhizosphere at the same time. This shows that NO3--N transference from rhizosphere soil to plant root exists two ways—mass flow and diffusion..Corn can uptake NO3--N from soil in the dry zone. The accumulation of NO3--N in rhizosphere near roots exists and its extent becomes larger with the texture of soil becomi更多还原