Using HYDRUS to simulate the dynamic changes of Ca²⁺ and Na⁺ in sodic soils reclaimed by gypsum

Abstract

Wang J., Bai Z., Yang P. (2016): Using HYDRUS to simulate the dynamic changes of Ca 2+ and Na + in sodic soils reclaimed by gypsum. Soil & Water Res., 11: 1-10.Sodic soils are characterized by the occurrence of excess sodium to levels that can adversely affect soil structure.In recent years, with the advent of alternatives for reclaiming sodic soils, such as the addition of by-products of flue gas desulfurization, fly ash, phosphogypsum, etc., using CaSO 4 to reclaim sodic soil has again become a hot topic. In this study, cation exchange batch experiments and column leaching experiments were conducted to analyze the adsorption-exchange and dynamic changes of Ca 2+ and Na + during the reclamation of sodic soils with CaSO 4 . The HYDRUS-1D software was subsequently used to simulate and predict dynamic changes in Ca 2+ and Na + . The cation exchange batch experiments consisted of six treatments with six CaSO 4 rates (0, 0.25, 0.5, 1, 1.5, and 2 g/l), and the column leaching experiments consisted of two treatments with two CaSO 4 concentrations (0.5 and 1.5 g/l). The results of the static cation exchange batch experiments indicated that the ion adsorption-exchange coefficients K Ca-Na , K Ca-Mg , and K Ca-K were 1.9, 0.8, and 1.1, respectively. Applying CaSO 4 and leaching are efficient methods to reclaim sodic soil. The pH and electrical conductivity of the soil solution gradually decreased with longer leaching time in all of the treatments. HYDRUS-1D successfully simulated both the dynamic changes of the Ca 2+ and Na + concentrations at different soil depths under different treatments and leaching time, and the effects of soil hydraulic conductivity and soil pH on the transport of Ca 2+ and Na + . The correspondence between the observed and simulated variables was remarkable.

Improvement of the chemical properties and buffering capacity of coastal sandy soil as affected by clays and organic by-product application

“…The use of tapioca dregs also offers environmental advantages by reducing (+) indicates there is an interaction effect; the values in the same column with the same letter are not significantly different at P < 0.05; the mean followed by the same superscript letters are not significantly different according to the orthogonal contrast at P < 0.05; SC -soil conditioner; I -Inceptisol; V -Vertisol; T1 -tapioca 1%; T2 -tapioca 2%; TD1 -tapioca dregs 1%; TD2 -tapioca dregs 2%; P1 -PVA 0.1%; P2 -PVA 0.2%; C -control; initial Ca 2+ = Ca 2+ derived from sandy soil+clay+polymers; residual Ca 2+ = initial Ca 2+ -leached Ca 2+ +) or (-) indicates there is an interaction or no interaction effect; the values in the same column with the same letter are not significantly different at P < 0.05; the Mean followed by the same superscript letters are not significantly different according to orthogonal contrast at P < 0.05; SC -soil conditioner; I -Inceptisol; V -Vertisol; T1 -tapioca 1%; T2 -tapioca 2%; TD1 -tapioca dregs 1%; TD2 -tapioca dregs 2%; P1 -PVA 0.1%; P2 -PVA 0.2%; (Jones et al 2012;Mahmoodabadi et al 2013;Zhang et al 2015;Batarseh 2017). The high mobility causes Na + to be easily carried away by the movement of the vertical water flow (Mahmoodabadi et al 2013;Wang et al 2016). The amount of leached Na + in the single treatment of I was not different from that in V. However, since the initial Na + in the amelioration using I was higher than in V, thus, the amount of residual Na + was higher as well (Table 8).…”

Monitoring and Modeling of Saline-Sodic Vertisol Reclamation by Echinochloa stagnina

“…Refs. [27,28] used Hydrus-1D to simulate the effects of gypsum amendment on soil salinity dynamics in a saline-sodic clay soil. Their predictions agreed with the measurements, showing a decrease in soil ECe in saline-sodic clay soil after gypsum application.…”

“…Many studies have used simulation models to investigate water flow and salt dynamics in clay soils [23][24][25][26][27]. Few, however, have simulated salt dynamics in salt-affected soils undergoing remediation techniques.…”