Sensitivity Analysis of Nonlinear Model Parameters in a Multilayer Root Zone

A numerical model is developed for simulating soil moisture movement for a multilayer crop root zone in subtemperate-subhumid agro-climates. Water dynamics is used for a nonuniform root distribution pattern to compute the root extraction rate by plants in a moisture-scarce environment. The root uptake function is incorporated in governing the soil-moisture equation. Sensitivity analysis (SA) has been carried out to evaluate the relative importance of model input parameters in predictions of moisture uptake by plants. The paper describes the results of sensitivity analysis of model parameters for a maize crop and their spatial dimension. An iterative procedure has been used for the sensitivity analysis. The model was run for a range of values (±10% and ±5% from base value) of different model parameters to obtain plant moisture uptake. Results indicate the model is least sensitive to saturated moisture content (θs), coefficient (n), field capacity (FC), and permanent wilting point (PWP). The model is sensitive to residual moisture content (θr), root uptake model parameters (α) and (β), and saturated hydraulic conductivity (Ks) since variation in these parameters has significant impact on model output.