Effects of irrigation and tillage practices on yield of potato under high production conditions in the Pacific Northwest

The soil and climate conditions prevalent in the Pacific Northwest region are favorable for production of high potato (Solanum tuberosum L.) yields. Much of this production occurs on coarse, low organic matter, sandy soils which can be subject to wind and water erosion, and excessive leaching of water and soluble agrichemicals below the root zone, particularly when irrigation is not managed adequately. Tuber production and quality are adversely impacted when potatoes are subject to water stress. Therefore, optimal irrigation scheduling is important to support high production of good quality tubers and to minimize potential adverse impacts on water quality. Effects of two irrigation regimes and three tillage practices on production of two potato varieties were studied under four years rotation with either corn (Zea mays L.) or wheat (Trilicum aestivum L.), In two out of three years, as compared to irrigation to replenish full evapotranspiration (ET), deficit irrigation (85% of ET) decreased total tuber yield by 8 to 11% and 10 to 17%, and U.S. No. I tuber yield by 5 to 17% and 16 to 25%, in Russet Burbank Lind Hilite Russet cultivars, respectively. Tillage treatments evaluated were (i) conventional including raised ridges with dammer-dike; (ii) optimal, i.e.. lower depth of the tillage and shallow furrow, and (iii) reduced tillage, i.e., flat planting. During the first two years of the study, the effects of tillage treatments were non-significant on the total as well as U.S. No. I tuber yield in both cultivars. On the third year, the tuber yield was significantly lower in flat planting treatment LIS compared to that in the other tillage treatments. This study demonstrated that in coarse textured soils with adequate water infiltration, excessive tillage and/or dammer-diking may not benefit potato production.