Effect of Vermiculite, Bentonite and Zeolite on Evaporation and Soil Characteristic Moisture Curve

Water scarcity is the most important problem in agricultural development, especially in arid areas. Therefore, the study of strategies to increase water use efficiency must be considered. Providing methods to control and reduce soil evaporation can be a suitable way to increase water use efficiency. Soil surface Evaporation can be considered as the main part of water balance components in arid areas that cause water wastage. One of the ways to control and reduce evaporation from the soil is to use natural amendments. Therefore, this study was conducted to investigate the effect of three minerals including bentonite, vermiculite and zeolite on the amount and intensity of evaporation from the soil surface in a period of 4 months from Tir (July) to Mehr (October).

This study was conducted as a completely randomized design (CRD) with 10 treatments and three replications at Shahrekord University. The studied treatments in this research include 3 types of natural amendments (bentonite, vermiculite and zeolite) at three levels of 0.5, 1 and 2% with a control treatment (soil without any amendment). These natural minerals were mixed in soil of whole pots. The amount of evaporation was measured by measuring the amount of irrigation water of each pot and outlet water of them and based on the water balance equation. Moisture content was measured with a hygrometer at two depths of 5 and 15 cm. Finally, the soil moisture characteristic curve for each treatment by using of pressure plate was obtained and compared.

The results showed that among the three studied minerals, the highest reduction in soil evaporation was related to bentonite. The two minerals vermiculite and zeolite also significantly reduced evaporation compared to the control treatment, but the difference between them was not significant. Among the studied treatments, the highest reduction effect on evaporation was observed in 2% bentonite mixed with soil and the lowest effect was observed in 0.5% zeolite treatment. This treatment did not show a significant difference with the control, but 2% bentonite treatment significantly reduced the rate of evaporation compared to the control by 6.4%. The results the soil moisture in the treatments was the opposite of the evaporation results. In the treatments where the evaporation rate was lower, the moisture content increased. Due to the significant effect of the three minerals on the soil moisture, the soil moisture curve in the studied treatments has also changed compared to the control.

The use of natural soil amendment in addition to preventing soil contamination, helps to improve soil structure to reduce evaporation. Overall, due to the highest effect of using 2% bentonite on significant decreasing of soil evaporation therefore, this soil amendment can be recommended to control of evaporation from soil.