Effect of Mulch and Irrigation Water Amounts on Soil Evaporation and Transpiration

Soil evaporation, transpiration, evapotranspiration, and yield of pepper as affected by mulch and five amounts of irrigation water were studied in greenhouse pot experiments during 1996 (March 26–July 13). Five different amounts of irrigation water were imposed on covered and open soil surface clay loam soil in five replicates. Water losses by evaporation and/or transpiration were measured daily by weighing. Irrigation water was applied once weekly. The amount of irrigation water added to each treatment was determined from the differences in weights.
Covering soil surface reduced the required amount of irrigation water. With deficit (under) irrigation, the reduction in applied irrigation water was about 14%. and increased to 29 % with excess (over) irrigation. Transpiration in covered soil surface treatments were higher than transpiration in open soil surface treatments with limited irrigation water applied, With limited (deficit) irrigation, increasing irrigation water applied decreased the percentage of soil evaporation and the contribution of soil evaporation to crop evapotranspiration. With excess irrigation, increasing water applied increased the percentage of soil evaporation and its contribution to the total evapotranspiration. Soil evaporation reduced pepper yield significantly, and this might be owing to the reduction in the available soil water associated with limited-to-complete irrigation.