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本文从提高土壤水分和养分资源利用效率出发，研究与此有关的土壤水氮条件与作物根系生长的关系， 以及适宜的水氮范围。根据冬小麦、夏玉米试验结果表明，根长（ Ｌｒ） 发展动态，根长密度（ Ｌｒ Ｄ） 及其垂直分布和根长／ 冠重比值（ Ｌｒ／ Ｄ Ｍｐ） ，均受土壤水氮条件的影响。水氮的严重胁迫，都会使根系发展受抑制，而 Ｌｒ／ Ｄ Ｍｐ 却加大。在水分稍有亏缺条件下，土层中部根长密度增加，但后期衰亡速率也较快。 Ｌｒ 和 Ｌｒ／ Ｄ Ｍｐ 的综合评价，可用以衡量根系状况。本文运用 Ｌｒ 和 Ｌｒ／ Ｄ Ｍｐ 与水氮条件关系的等值线图的叠加法，将两图高值区的重叠区，作为作物在该生育阶段的适宜指标范围和适宜的水氮范围。
Based on the improvement of soil water and nutrient resource utilization efficiency, this paper studied the relationship between the soil water and nitrogen conditions and crop root growth and the suitable range of water and nitrogen. According to the results of winter wheat and summer maize, the development of root length (Lr), root length density (Lr D) and its vertical distribution and root length / crown weight ratio (Lr / D Mp) were affected by soil water and nitrogen . Severe water and nitrogen stress, will make the root development inhibited, but Lr / D Mp has increased. Under the conditions of a little water deficit, the root length density in the middle part of soil increased, but the rate of decline in later stage was also faster. Lr and Lr / D Mp comprehensive evaluation, can be used to measure the status of the root system. In this paper, the superposition of contour maps of Lr and Lr / D Mp and water-nitrogen conditions is used to define the suitable range of crop and suitable water and nitrogen for the crop during the growth stage.