MEASUREMENT AND ESTIMATION OF CAPILLARY UPFLOW FROM WATER-TABLES UNDER MAIZE ON IRRIGATED SOILS

An experiment with maize on two soils in lysimeters L1 and L2 (Hanwood clay loam and Mundiwa clay loam respectively) was conducted to measur e daily capillary upflow and to establish a relationship between capil lary upflow and significant soil, watertable, crop and environmental f actors. Total evapotranspiration from L1 and L2 during the season was 748 and 631 mm respectively. Capillary upflow contribution to evapotra nspiration in L1 and L2 was 215 (29%) and 101 (16%) mm respectively. D aily capillary upflow ranged from 0 to 5 mm day-1 in the Hanwood clay loam and 0 to 2 mm day-1 in the Mundiwa clay loam during the experimen t. Measured daily capillary upflow was significantly (P < 0.001) diffe rent between the two soils studied. A stepwise multiple regression, by using the combined data from L1 and L2, showed that the depth to the watertable, water content of the soil layers at 0.1 and 0.4 m and root length density L(v) at 0.65 m significantly influenced capillary upfl ow (n = 68, R2 = 0.79, p < 0.05) in both soils.