Effects of snow compaction ‘yuki-fumi’ on soil frost depth and volunteer potato control in potato–wheat rotation system in Hokkaido

Emergence of unharvested potatoes that survived during winter becomes source for nematodes and diseases, causing serious weed problems in rotational crop fields. Herein, we describe frost killing of unharvested potatoes in potato–wheat rotation fields using snow compaction ‘yuki-fumi’ under multiple climate conditions. The effect of snow compaction in controlling volunteer potato over winter wheat was verified in 17 farm fields in Hokkaido, Japan from 2015–16 to 2017–18. A reduction in the temperature of soil under ‘yuki-fumi’ was slower than that under snow removal ‘yuki-wari’, which was used in previous studies. However, snow compaction achieved a substantial reduction in volunteer potato sprouting in most of the experimental sites. The sprouting of volunteer potatoes was reduced in snow-compaction blocks with soil temperatures below −3°C. For winter wheat sowing in potato–wheat rotation, the soil is tilled to a shallower depth than that for other crops, and thus, unharvested potato tubers are not pushed down during field preparation for wheat sowing. Consequently, even if the soil temperature drops slightly, snow compaction can regulate the sprouting of volunteer potatoes. Snow compaction did not exert any apparent influence on wheat growth and grain yield. At some sites with a deeper snowpack, development of soil frost and reduction in soil temperature did not progress with continued snow compaction owing to fallen snow. We validated the usefulness of snow compaction as a countermeasure to control volunteer potatoes in snowy regions.