Salts transport from a moderately saline-alkaline rangeland soil using rainfall simulation

Authors: ARSLAN, AWADIS - University Of Nevada; Weltz, Mark; Nouwakpo, Sayjro

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2020
Publication Date: N/A
Citation: N/A

Interpretive Summary: Rainfall simulation was used to understand how abiotic and biotic characteristics influence runoff and erosion process on a moderately saline-alkaline site near Ferron, UT. Three hillslopes were identified at the study site to represent low (L, canopy cover <5%, average = 2.39%), medium (M, 5% < canopy cover <19%, Average = 9.09%), and high (H, canopy cover >19%, average = 22.41%) vegetation covers. A Walnut Gulch Rainfall Simulator was used to simulate rainfall at an intensity of 114 mm/h. The average ratio of runoff to applied rainfall was 48.94%. and the average sediment concentration was 15.98%. The concentration of salts in the runoff water from the high-density cover was significantly lower than the concentrations from medium and low canopy covers’ density. The concentration of Ca2+, Mg2+, and SO42- in the runoff water started low then increased with time, while that of Na+ and Cl- started high and decreased with time. Average saturated paste Electrical Conductivity of the soil (ECe) under canopy before the runs (9.56 dS/m) was insignificantly higher than that of the interspace (8.24 dS/m). Average Sodium Adsorption Ratio (SAR) of the soil before the runs under canopy (27.62) was higher than that of interspace (21.92) The difference in ECe between interspace and under canopy became significant after simulation resulting from its increase under canopy and decrease in the interspace. Our results showed higher Exchangeable Sodium Percentage (ESP) under canopy before simulation, compared with interspace. The determination of both ESP and SAR on 90 samples enabled us to determine equations to convert the easy and economic determination of SAR to the costly and time-consuming determination of ESP. The results of this study will help in selecting the processes needed to be incorporated into existing models, such as the RHEM, for better prediction of runoff volume and quality and sediment yield under saline sodic conditions. Moreover, this information will help range managers select the practices that enhance soil properties, its forage production, and reduce the deterioration of surface and ground water.

Technical Abstract: Rainfall simulation was used to understand how abiotic and biotic characteristics influence runoff and erosion process on a moderately saline-alkaline site near Ferron, UT. Three hillslopes were identified at the study site to represent low (L, canopy cover <5%, average = 2.39%), medium (M, 5% < canopy cover <19%, Average = 9.09%), and high (H, canopy cover >19%, average = 22.41%) vegetation covers. A Walnut Gulch Rainfall Simulator was used to simulate rainfall at an intensity of 114 mm/h.The average ratio of runoff to applied rainfall was 48.94%. and the average sediment concentration was 15.98%. The concentration of salts in the runoff water from the high-density cover was significantly smaller than the concentrations from medium and low canopy covers’ density. The concentration of Ca2+, Mg2+, and SO42- in the runoff water started low then increased with time, while that of Na+ and Cl- started high and decreased with time. Average saturated paste Electrical Conductivity of the soil (ECe) under canopy before the runs (9.56 dS/m) was insignificantly higher than that of the interspace (8.24 dS/m). Average Sodium Adsorption Ratio (SAR) of the soil before the runs under canopy (27.62) was higher than that of interspace (21.92The difference in ECe between interspace and under canopy became significant after simulation resulting from its increase under canopy and decrease in the interspace. Our results showed higher Exchangeable Sodium Percentage (ESP) under canopy before simulation, compared with interspace. The determination of both ESP and SAR on 90 samples enabled us to determine equations to convert the easy and economic determination of SAR to the costly and time-consuming determination of ESP. The results of this study will help in selecting the processes needed to be incorporated into existing models, such as the RHEM, for better prediction of runoff volume and quality and sediment yield under saline sodic conditions. Moreover, this information will help range managers select the practices that enhance soil properties, its production, and reduce the deterioration of surface and ground water. These results are considered provisional pending additional researches that include more variations in soil types, slope, and vegetation communities, before a global solution can be identified to predict salts mobilization and transport from rangelands.