| 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 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... |
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