The soil in the early stage of land draining at the polder (the reclamation in water area) is marshy and heavy clay soil. This soil has a lot of problems utilizing the upland field. In the case of thus soil, dry of soil is indispensable condition for crops at the upland field. A method for dry of soil is utilize of transpiration by vegitations.
This report is positively cleared the drying effects of soil by grass at the YASUKI division in the NAKAUMI polder. The main results are as follows : 1) The drying effects of soil at the polder by grass could not grasp as remarkable phenomenon, but there are recognized in total of soil layer. 2) The dry of soil is affected by water level of drainage canal which are surrounding the upland field. 3) The acceleration of dry of soil is necesary to use a dry-method by subsurface drainage system.