K+ UPTAKE BY ROOT SYSTEMS GROWN IN SOIL UNDER SALINITY .2. SENSITIVITY ANALYSIS

A numerical algorithm for the solution of multicomponent transport of Ca2+, Mg2+, Na+, K+, Cl- in soil and their uptake by plant roots has b een developed. The model emphasizes adsorption-desorption due to catio n exchange mechanism, dissolution-precipitation of CaCO3, and pH chang es at the root surface controlled by the anion-cation influx balance. A fully implicit finite difference scheme is used for numerical implem entation. Sensitivity analysis was conducted to evaluate the effect of each parameter on nutrient uptake. Each parameter (independent of all others) was varied between 0.25 to 4 times its speculated 'average' l evel. Predicted K+ uptake was found to be more sensitive to changes of root radius and the parameter indicating maximal influx of K+. Effect ive diffusion coefficient and soil moisture are less influential. The influence of CaCO3 dissolution and different kinds of boundary conditi ons were also considered.