Soil compaction is a problem in many potato fields of the Pacific Northwest. It was
hypothesized that zone subsoiling could increase infiltration, potato (Solanum tuberosum
L, cv Russet Burbank) yield, or quality and decrease bed bulk density, runoff, and sediment
loss of furrow irrigated fields, while maintaining trafficability and irrigability of furrows. A two
year field study was established in Fall 1988 near Kimberly, Idaho, on a Portneuf silt loam
soil (coarse-silty, mixed mesic Durixerollic Calciorthids). In the Fall of each year plots were
in wheat stubble (1988) or bean stover (1989) the previous season, and were either disked
(10-12 cm), chiselled (25-30cm), or moldboard plowed (20-25cm) in the Fall. Fall tillage
plots were split in Spring, half of each plot receiving in-row zone subsoiling after planting.
The overall effect of zone subsoiling on infiltration in 1989 was small as a result of variation
of its effect in the different fall tillage treatments. In 1990 zone subsoiling increased
infiltration an average of 10% in all fall tillage treatments. Sediment loss by treatments were
generally related to runoff, decreasing with zone subsoiling. Zone subsoiling was generally
more effective at reducing erosion than at increasing infiltration as indicated by 2-3 fold
decreases in the ratio of sediment loss to water infiltrated with zone subsoiling. The relative
effectiveness of zone subsoiling at increasing infiltration and reducing sediment loss was
greater in 1990 when the study was conducted on a field with a greater slope than in 1989
and at higher water application rates than in 1989. Yield of #1 tubers was increased 3.8 t
ha-l and quality was improved by zone subsoiling in 1989. Overall yield was not significantly
increased (P = 0.05), but showed a favorable trend. Yield data were not available for 1990
at this writing, but early season growth analysis indicate a positive response to subsoiling.
Zone subsoiling would require extra attention on the part of the irrigator early in the season
to insure uniform irrigation but offers the potential to conserve both soil and water while
raising quality and possibly yield in Russet Burbank potatoes
