On estimating the uptake of nutrients solubilized near roots or other surfaces

SUMMARY The additional nutrient absorbed by a surface releasing a solubilizing agent is predicted. The ‘solubilizing effect’ is defined. The nutrient solubilized may diffuse away from the surface as well as towards it. If the change in solution concentration of nutrient and solubilizing agent at the surface are abrupt, the fraction of nutrient solubilized that is absorbed at a planar surface equals 1/(1 +√ D Y / D X ), where D Y , D X are the diffusion coefficients of the solubilizing agent and the nutrient. At a spherical surface this fraction has to be multiplied by 1/(1 +√π D Y /t 2 a ), and at a cylindrical surface, appropriate for a root, by approximately 1/(1 +√π D Y /t 4 a ), where a is the radius.