Characteristics of the rain water and soil moisture flows in the fields covered with film mulch

摘要

Film mulch is being used in many farm lands because it improves the environment for cultivation by suppressing water evaporation from soil surface, maintaining a mild soil moisture condition, and maintaining the soil temperature higher than the bare sou surface, in addition to protecting against pests and diseases. Crop cultivation in cool high lands (such as the Shinshu Plateau) can be made possible with the introduction of film mulch. However, as the direct infiltration in the root zone are lower in fields where film mulch is used than in bare soil fields, and this raises fears that droughts would be exacerbated. Experimental comparisons of the soil moisture condition and flow between mulched bed and furrow space using the soil moisture measurement technique at many positions and many depths were carried out in the fall of 1995 in field planted with Chinese cabbage (Brassica pekinensis Rupr.),and in the spring of 1996 in field planted with cabbage (Brassica oleracea L.). The results are summarized as follows; (1) The shallow topsoil of the mulched beds had less soil moisture than furrow space and bare soil even after light rains at low soil moisture condition. The sowed areas (hold of the mulch film) in mulched beds, however, were moisture than the surrouding of sowed area. But one or two days after rainfall, soil moisture condition in mulched bed and furrow space were almost same. (2) As the crops grew, the soil moisture became lower than furrow space due to the water uptake by the crops' root system. In the soil layer below the root zone, i.e. at a depth of more than 0.3 m, soil moisture is moved from the furrow space to the mulched bed by the gradient of soil moisture potential caused by the soil moisture uptake by the root system. These results propose that occasional plowing in the furrow space causes an increase in the infiltration rate of rain water, and facilitates the movement of moisture from the furrow space to root zone of the mulched beds.