Abstract
In this study, for large-scale （63.9ha/240 parcels）, a Four-crop rotation system with two production years （rice–wheat/barley–soybean） on paddy fields, we analyzed the relationship between rainfall measured using an IoT sensor and farm work history obtained from a GPS log etc. based on the standard values of workable rainfall published by the Ministry of Agriculture, Forestry and Fisheries （MAFF standard value）. In addition, we tried to propose desirable future values of workable rainfall. Fertilization, tillage, puddling, transplanting, and pest control for rice cultivation as well as herbicide spraying and levee weeding for rice, soybean, and wheat/barley cultivation were considered workable even under rainfall levels exceeding the standard value. Thus, the cultivation technology improved in each aspect: devising a work system in preparation for rainfall risk, using the agricultural machine popularized since the announcement of the MAFF standard value, popularization of liquid herbicides, performance improvement of the agricultural machine itself as seen in autopilot rice transplanters, and popularization of pesticides that are not easily affected by rainfall. In contrast, the workable rainfall for rice, soybean, and wheat/barley cultivation was considered to be below the standard value. Management decisions, such as those for maintaining crop quality and reducing the use cost of grain cooperative drying facility, also have a considerable impact on the response to rainfall risks. To improve the MAFF standard value, the values suitable for situations in recent years should be updated, and the temporal classification of rainfall levels on farm working days should be subdivided. Further, by considering the operation system, agricultural machine characteristics, soil types, etc. as factors, a more accurate standard value can be established.
