Agricultural Practices Using Agrometeorological Information As an Adaptative Countermeasure to Climate Change -an Example of Volunteer Potatoes Management in Northern Japan.

Climate change often causes unexpected problems for agricultural production. In the Tokachi region, northern Japan, soil-frost depth has been decreasing after 1980’s, facilitating the winter survival of small potato (Solanum tuberosum L.) tubers that remained unharvested and emerge as weeds in the following cropping season. Soil frost control by snow plowing (yukiwari), which removes snow cover and allows deep soil frost to kill the potato tubers, is spreading as a practical countermeasure. To establish a reliable volunteer potato control technique including farmers’ decision making, we implemented on-farm testing of soil frost control guided by a numerical soil temperature model on the survival ratio using air temperature and snow cover thickness as input data. Moreover, we presented the final limit for yukiwari operation (the latest period of yukiwari operation to achieve sufficient frost depth) based on the numerical model for the Tokachi region, with annual climate fluctuations taken into account. The numerical model for estimating soil frost depth facilitates the planning of the work schedule of the practice of yukiwari to kill potato tuber sufficiently. This technique has widely spread by local farmers in the Tokachi region with the execution rate of 70%. However, in winter, the local variation of air temperature is large especially in region having complex topography. To make the practice more reliable in the broader areas, further development of agro-meteorological information is required as input data of the numerical soil temperature model.