Sand and Cotton Bur Mulches, Bermudagrass Sod, and Bare Soil Effects on: I. Evaporation Suppression

Abstract

AbstractMoisture, water table, and temperature changes were recorded for 3 years under four surface cover conditions used for salinity reclamation under the rainfall conditions (58 cm/yr during the study) in the Lower Rio Grande Valley of Texas. Surface cover conditions were (i) 1.5‐cm‐thick mortar sand mulch; (ii) 44,800 kg/ha cotton bur mulch (Gossypium hirsutum); (iii) coastal bermudagrass sod (Cynodon dactylon L.); and (iv) bare fallow.Relative profile moisture depletion among treatments and soil moisture suctions measured in the surface 50 cm of the soil show that even shallow soil depths remained moist during long, rainless periods under the sand and cotton bur mulches. The amount of water in the surface 61 cm of soil for 37 measurement dates averaged 1.32 cm more under the burs, 1.38 cm more under the sand much, and 2.85 cm less under the grass sod, respectively, than under the bare soil condition. Monthly means of daily maximum and minimum soil temperatures measured at the 10‐cm depth were both in the order sand mulch > bare soil > bur mulch > bermudagrass sod, but the higher soil temperatures under the sand mulch did not obviate its effectiveness in evaporation suppression. Since soil moisture suctions were low under the mulches, even moderate rainfall amounts rewet the soil to field capacity and should have effected leaching.