Irrigation water management for the diversified use of plastic film mulch

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For the upland crop production, plastic films are variously used in Japan. High qualification and harvesting time control are the main purpose of using the plastic films. To clarified the effect of plastic films on air and soil temperature, soil moisture and solar radiation, the characteristics of various crop canopy architectures were measured. Using the prototype and simplified models, first, shortwave and diffused solar radiation absorption and penetration were studied. Simulation model to cope with various types of crop canopy was established. This model was also applied for quantifying the long wave radiation exchanges between crop body and sky. Second, the effect of crop canopy, especially row crop condition, on the spatial distributions of soil temperature, soil moisture and soil surface evaporation were clarified. These results were effectively applied for estimating water consumption from soil surface on the micro-irrigated field. Third, reflection and penetration characteristics of short wave and long wave radiation of various types of plastic film were investigated. And the effects of these different types of films on soil environment below the crop canopy was clarified. Fourth, irrigation scheduling appropriate for various types of plastic film fields were studied. Evapotranspiration on tunnel type mulch, completely co soil surface mulch and partly covered soil surface mulch fields were investigated and optimal irrigation methods were studied by both simulation and observation. Fifth, absorption performances of nutrients by the crops were investigated using lysimeters. With comparing the results of different types of mulch, it was clarified the large amount of applied fertilizers were percolated to the groundwater when the plant holes on the mulch were not small.