Modeling and Experimental Determination of Salt Accumulation Induced by Root Water Uptake

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Abstract
We investigated salt accumulation processes induced by root water uptake above the groundwater table. We compared experimentally determined results from a pot experiment with those predicted by a numerical simulation. Spring wheat ( Triticum aestivum L.) was grown in sand‐filled pots, and a constant groundwater table of saline water was maintained. We measured physiological factors of wheat such as daily transpiration rate, leaf water potential, and root length distribution. Water content and salt distribution in the pots were determined. We developed a numerical model for salt accumulation that was based on physical models of water and solute movement in the soil and included a root water uptake term and a stomatal behavior model. The root water uptake rate was calculated using an Ohm's law type model; the transpiration rate as a function of leaf water potential and all soil physical properties regarding water and solute movement in soil were measured independently. Observed and calculated results showed that the salt accumulation pattern changes dynamically with changes in root water uptake patterns and vice versa. In the lower root zone, salt content was at a quasi‐steady state, and salt accumulation did not proceed even though root water uptake occurred there; concentrated salt was transported upward by soil water flux induced by root water uptake in the upper zone. Salt accumulated mainly in the upper root zone where root water uptake ceased due to the lower water potential of the soil. The site of salt accumulation moved downward as salt accumulation proceeded and soil water potential decreased

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