Calculation of the root density required for growth in soils of different P-status

Abstract

Root density determines the physical availability of mobile soil phosphorus to the plant. Calculations about diffusion of phosphorus to the roots were made, with the assumption that the rate of uptake is determined by the requirements of the crop in the linear growth phase. The poorer the soil, the higher must be the root density to be able to extract sufficient phosphorus from the soil. This relation is quantified analytically for a linear adsorption process and through numerical simulation for the curvilinear adsorption under agricultural conditions. An agricultural evaluation of plant-available soil phosphorus by extraction with water is possible, but the best volume ratio of soil to water to be used depends on the root density