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WATER AND SOLUTE DYNAMICS UNDER A DRIP-IRRIGATED CROP: EXPERIMENTS AND ANALYTICAL MODEL

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASAE.  VOL. 43(6): 1597-1608 . (doi: 10.13031/2013.3060) @2000
Authors:   K. Mmolawa, D. Or
Keywords:   Drip irrigation, Volume balance, Two-dimensional model, Solute, Root uptake

Spatial and temporal distributions of water and solutes in crop root zone are controlled by irrigation and fertigation methods, crop root distribution, and uptake patterns. Soil water content (q) and electrical conductivity of the bulk soil solution (EC b ) were simultaneously measured by TDR at several locations in the root zone of a drip-irrigated corn crop. The data was used to calculate temporal and spatial distributions of soil solution concentration of nitrate and changes in nitrate at different monitoring volumes. A local solute mass balance model for predicting solute concentration and mass dynamics and distribution has been tested with field and greenhouse data. Three primary assumptions facilitated the derivation of a local solute mass balance model, (1) no spatial interaction of flow is considered, (2) solutes are convectively transported with soil water, and (3) solutes are nonreactive and nonadsorbing. During plant (corn) growth and active water and nutrient uptake, q and EC b dynamics are different than in the absence of plants. The model was capable of capturing observed fluctuations at various locations under surface and subsurface drip irrigation. This model can help predict the amount of solutes taken up by plants and therefore can be a useful tool for scheduling fertigations and to also help avert possible ground water pollution.

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