地中灌概圃場

The experiment was conducted to clarify the characteristic of soil water movement and evapotranspiration in a subsurface irrigated field. The sorgo and maize were planted in the field and was irrigated by tubes berried at the depth of 50 cm. The actual evapotranspiration rate and potential evaporation rate were estimated by the Bowen ratio method and the Penman method, respectively, using micro-meteorological data obtained in the field. The amount of actual evaporation and the crop coefficient changed due to the growing season. The volumetric water contents were measured by TDR method at five depths, i.e. 15, 25, 35, 45 and 55 cm. The time courses of volumetric water contents were apparently different in cases Qf rainfall period and irrigation period. The fact that the soil water contents near the soil surface were not influenced by irrigation demonstrates that the evaporation loss didn't occur at soil surface. While the soil water contents at the depths of 45 and 55 cm decreased rapidly after irrigation stopped. This indicates that the soil water loss due to drainage might occur. ln addition the soil water movement was simulated numerically using the simple model, which didn't include crop elements. The results of simulation showed the changes of soil moisture distribution on the soil profile. This simulation model would be available for the planning of subsurface irrigation if this model modified by comprising the crop elements.