USE AND MANAGEMENT OF SOIL WATER AND NITROGEN RESOURCESⅠ. Soil Water and Nitrogen Conditions and Root Development

From the point of raising the use efficiency of soil water and nutrient, the relation between the roots development of the crops and soil water and nitrogen conditions, and the suitable range of soil water and nitrogen for root growth are studied in this paper. The experiment results from winter wheat and summer corn show that the dynamics of the root length (Lr) development, root length density (LrD) and its vertical distribution and the ratio of root length and the dry weight of the aboveground part of plant (Lr/DMp) are all influenced by the soil water and nitrogen. In the condition of serious stress of soil water and nitrogen, roots development is constrained, but the Lr/DMp ratio is increased. In the condition of slight stress of soil water and nitrogen, the LrD in the subsoil is increased, but the senescence rate of the root is higher during the final growth stage of crops. The comprehensive evaluation of the Lr and Lr/DMp is a nice way to judge the root development. In this paper, the overlay method of the two contour maps (Lr and Lr/DMp versus RW (relative soil water content) and soil mineral N)is used and the overlay area of the high value regions in the two maps indicates the suitable range of indexes for Lr and Lr/DMp and reasonable ranges of soil water and nitrogen.