CULTIVATION AND EVAPORATIVITY EFFECTS ON THE DRYING PATTERNS OF SANDY LOAM SOIL

Abstract
Laboratory and field experiments were conducted to study the influence of the depth of cultivation on the loss of water from and below the disturbed layer, the cumulative evaporation (CE) and time (t) relationship and the advance of isohydric fronts into soil, under evaporativity (E0) conditions. Cultivation reduced evaporation under all the E0, with highest reduction under the low E0. The maximum evaporation reduction was obtained after 29 days under high E0 and after 55 days under medium and low E0. The differences in loss between the 6- and 12-cm cultivation depths were greater under higher E0. The relationship CE = Kt0.5 gave an excellent fit for both the 6- and 12-cm cultivation treatments under all E0. The regression coefficient K increased linearly with E0, and at a given E0 was lower for 12-cm than for 6-cm cultivation. The cultivated layers dried more rapidly than the corresponding depths of uncultivated soil, but the layers below the loosened soil always had more water in cultivated than in uncultivated and in 12-cm than in 6-cm cultivation. The magnitude of differences in soil water across the junction of cultivated layers and the undisturbed soil below was influenced both by cultivation depth and E0. The position of 0.18 and 0.15 cm3/cm3 isohydric fronts was always deeper in uncultivated than in cultivated soil, except within the loosened zone.