Erosion and infiltration of furrow irrigated potato fields as affected by zone subsoiling

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