Biomass Accumulation and Partitioning in Two Potato Cultivars as Influenced by Irrigation and Nitrogen Management.

The acreage under ‘Umatilla Russet’ and ‘Ranger Russet’ potato cultivars increased during the recent years in the Pacific Northwest (PNW). Research to determine the optimal management of fertilizer and water on the growth characteristics, yield, and yield attributes of these new cultivars are lacking. This study was conducted on a Quincy fine sand (mixed, mesic Xeric Torripsamments) in Columbia Basin region, Washington. Two irrigation regimes (to replenish full evapotranspiration (ET) or 80% ET), three pre-plant N rates (56, 112, and 168 kg/ha) and three in-season N rates (112, 224, and 336 kg/ha) were evaluated on the above two potato cultivars. Plant samples (0.5m row lengths) were taken on 22, 44, 66, and 98 days after emergence (DAE) for evaluation of biomass accumulation and partitioning into leaves, stem, roots, and tubers. On 22 DAE, the aboveground (leaves and stem) and tuber biomass accounted 49 to 69% and 23 to 39% total plant biomass, respectively. The high N rate evaluated in this study was well above the recommended rate used only for evaluation of potential max N rate. The corresponding values for 98 DAE were 6 to 12% and 82 to 95%. At this growth stage, the aboveground biomass increases by 83 and 46%, respectively for ‘Umatilla Russet’ and ‘Ranger Russet’ cultivars with an increase in total N rate (pre-plant and in-season) from 168 to 504 kg/ha under full ET irrigation. The corresponding increased under 80% ET irrigation were 175% and 438% for the two cultivars. For the same increase in N rate, the increase in tuber biomass were 3 and 5%, and 14 and 30%, respectively for full ET and 80% ET irrigation. Accordingly, increased N rates had greater influence on aboveground vegetative biomass but rather marginal affects on tuber biomass, and tuber yield as well as quality.