EFFECT OF MULCH AND IRRIGATION WATER AMOUNTS ON SOIL EVAPORATION AND TRANSPIRATION

Soil evaporation, transpiration, evapotranspiration, and yield of pepp er as affected by mulch and five amounts of irrigation water were stud ied in greenhouse pot experiments during 1996 (March 26-July 13). Five different amounts of irrigation water were imposed on covered and ope n soil surface clay loam soil in five replicates. Water losses by evap oration and/or transpiration were measured daily by weighing. Irrigati on water was applied once weekly. The amount of irrigation water added to each treatment was determined from the differences in weights. Cov ering soil surface reduced the required amount of irrigation water. Wi th deficit (under) irrigation, the reduction in applied irrigation wat er was about 14%, and increased to 29% with excess lover) irrigation. Transpiration in covered soil surface treatments were higher than tran spiration in open soil surface treatments with limited irrigation wate r applied. With limited (deficit) irrigation, increasing irrigation wa ter applied decreased the percentage of soil evaporation and the contr ibution of soil evaporation to crop evapotranspiration. With excess ir rigation, increasing water applied increased the percentage of soil ev aporation and its contribution to the total evapotranspiration. Soil e vaporation reduced pepper yield significantly, and this might be owing to the reduction in the available soil water associated with limited- to-complete irrigation.