Water and solute dynamics under a drip-irrigated crop: Experiments and analytical model

Spatial and temporal distributions of water and solutes in crop root zone a re controlled by irrigation and fertigation methods, crop root distribution , and uptake patterns. Soil water content (q) and electrical conductivity o f the bulk soil solution (ECb) were simultaneously measured by TDR at sever al locations in the root zone of a drip-irrigated corn crop. The data was u sed to calculate temporal and spatial distributions of soil solution concen tration of nitrate and changes in nitrate at different monitoring volumes. A local solute mass balance model for predicting solute concentration and m ass dynamics and distribution has been tested with field and greenhouse dat a. Three primary assumptions facilitated the derivation of a local solute m ass balance model, (1) no spatial interaction of flow is considered. (2) so lutes are convectively transported with soil water and (3) solutes are nonr eactive and nonadsorbing. During plant (corn) growth and active water and n utrient uptake, q and ECb dynamics are different than in the absence of pla nts. The model was capable of capturing observed fluctuations at various lo cations under surface and subsurface drip irrigation. This model can help p redict the amount of solutes taken up by plants and therefore can be a usef ul tool for scheduling fertigations and to also help avert possible ground water pollution.