Abstract
In this paper, three substantial parameters are built in the soil moisture budget model to estimate the water consumption within the root zone, accurately.
They are 1) the reduction factor of evapotranspiration in the rainy day, 2) the capillary contribution factor to the effective root zone, and 3) the crop coefficient change factor induced by the soil moisture depression and the crop growth stage.
Using this new soil moisture budget model, we clarified,
(1) Reduction factor of evapotranspiration in the rainy day decreases amount of water requirement slightly during soybean growing periods.
(2) Reduction factor of evapotranspiration in the rainy day, the capillary contribution factor to the effective root zone, and crop coefficient change factor induced by the soil moisture depression and the crop growth stage were built in the moisture budget model. They decrease the amount of water requirement more because soil moisture in the root zone were not be lost so much.
(3) When rainfall were thought to reach the root zone in the soil moisture budget model additionally, the amount of water requirement is smaller than the previous results ((2)).
