Irrigation water management for the diversified use of plastic film mulch

对于旱地作物生产，日本使用各种塑料薄膜。高质量和收割时间控制是使用塑料薄膜的主要目的。为了明确地膜对土壤温度、土壤湿度和太阳辐射的影响，测定了不同作物冠层结构的特征。利用原型模型和简化模型，首先研究了短波和漫射太阳辐射的吸收和穿透。建立了适应不同类型作物冠层的仿真模型。该模型还用于量化作物体与天空之间的长波辐射交换。其次，阐明了作物冠层，特别是行播条件对土壤温度、土壤水分和土壤表面蒸发空间分布的影响。这些结果可有效地用于估算微灌农田土壤表面耗水量。第三，研究了不同类型塑料薄膜对短波和长波辐射的反射和穿透特性。阐明了不同类型地膜对作物冠层下土壤环境的影响。第四，研究了适合不同类型地膜田的灌溉调度。采用模拟和观测相结合的方法，对隧道式地膜、全覆盖地膜和部分覆盖地膜农田的蒸散量进行了研究，研究了最优灌溉方式。第五，利用溶渗仪研究了作物对养分的吸收性能。通过对比不同类型地膜覆盖的结果，明确了当地膜上的植物孔较大时，施用的肥料大量渗入地下水。

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.