Water and solute dynamics in drip-irrigated fields

Accurate information about root zone soil water and solute dynamics is essential for drip fertigation management. The main objective of this study was to develop a two-dimensional macroscopic model for describing nonreactive solute movement and distribution in the wetted soil volume under transient flow conditions in the presence of root water uptake. This involved reviewing recent soil water and solute dynamics modeling approaches, then using the local volume balance approach to develop a semianalytical model for predicting solute dynamics, and comparing the local volume balance method for soil water dynamics with a widely used Hydrus-2D numerical model. Irrigation method, management, and irrigation water quality affect the water and solute dynamics. Plant uptake of water and solutes also greatly affects the water and solute dynamics. Root water uptake by plants was represented by parametric models. With known plant water uptake patterns and rate, the soil solution concentration was used to link water uptake by plants (corn) with simultaneous uptake of dissolved solutes. The calculated corn nitrate uptake rate is within literature values of corn uptake of nitrates. There was good agreement between measured and predicted water and solute dynamics in the presence and absence of plants when applying the analytical model.; Comparison of the analytical model and the numerical Hydrus-2D model shows that the analytical model depends on linearizing parameters for predicting soil water dynamics in presence and absence of plants. Depending on the range of linearizing parameters used, the analytical model performs unsatisfactorily at locations outside the parameter range. The analytical model does not have a water stress response function to regulate plant extraction as the Hydrus 2D model does.