Soil Frost Control: Its Application to Volunteer Potato Management in a Cold Region

The earlier onset of persistent snowcover since the late 1980s has narrowed the time window for soil-surface cooling without insulating snowcover, drastically reducing the soil frost depth in eastern Hokkaido, Japan. In crop fields managed by rotation, small potato tubers left unharvested in the fall survive the winter and emerge as weeds during spring–summer (volunteer potatoes). To eliminate them, soil frost depths are manipulated by artificially controlling snowcover thickness, guided by numerical soil-temperature model prediction. Field trials demonstrated that soil frost depths were predicted within accuracy of several centimeters. The optimal soil frost depth of 0.3–0.4 m is proposed as a compromise between the elimination of volunteer potatoes and permissible soil frost depth to prevent negative effects on agriculture in the following spring. The numerical model also facilitates decision-making related to the work schedule of snow plowing practices (yukiwari in Japanese). This method is adopted by local potato producers, who manage farmland on a large scale. This method represents a new agricultural technology that is useful for adaptation to climate change.