降雨および連続干天に伴う干拓農地の水ストレスのリスク予測

抄録

  Central polder in Isahaya Bay in south-west Japan was reclaimed in 1997. Farming was started in 2008 after improvement of soil salinity and hydraulic conductivity conditions. Although the present soil conditions in the root zone are favorable and agricultural productivity has been increased, the crop stress due to wetness and drought is still concerned. The aim of this study is to predict risk of the water stress on crop due to wetness and drought. Annual changes of the soil moisture condition and soil water balance in the crop field were simulated with SWAP (Soil-Water-Atmosphere-Plant) model. In the simulation scenario, potatoes were grown from 20 February to 30 June and from 10 August to 20 December. Simulation results indicated that the soil moisture condition varied with the precipitation and the stress due to wetness was concerned under frequent and heavy rainfall. However the effect of the wetness decreased relatively quickly because of prompt drainage of excess surface and subsurface water. Drought stress was remarkable during the continuous dry weather days. To reduce the stress due to the drought, a scenario analysis was performed assuming the intermittent irrigation. The simulated results indicated that proper irrigation and drainage management is necessary to prevent stress due to wetness and drought.