ZONE-SUBSOILING EFFECTS ON POTATO YIELD AND GRADE

Soil compaction and erosion are problems in many Pacific Northwestern potato fields. We wanted to determine if zone-subsoiling would reduce these problems and improve potato yields and or grade without adversel y impacting other production practices. Studies were conducted in Sout hern Idaho at six locations over two years on different soils and with different irrigation methods to assess the effects of zone-subsoiling immediately after planting on tuber yield and grade. Reservoir-tillag e comparisons were made at three locations where sprinkler water appli cation rates were higher than soil infiltration rates. Russet Burbank was represented by eight location-years and Russet Norkotah by two. Zo ne-subsoiling consistently improved tuber grade or increased tuber siz e. The biggest improvement was under furrow irrigation. Zone-subsoilin g also tended to increase total yield in eight of ten location-years. Reservoir-tillage improved yield and grade, but zone-subsoiling did no t without reservoir-tillage when water application rates were high. At no location did zone-subsoiling significantly decrease tuber grade or yield. Zone-subsoiling had no appreciable effects on hill configurati on or seed-piece dislocation. Surface cracking and ''water piping'' oc curred under furrow irrigation but were not significant problems. Resu lts were similar for both cultivars. Additional studies will be needed to successfully incorporate zone-subsoiling into commercial productio n practices.