Row Orientation Influences Sunlight Interception and Productivity of Potato

Abstract The concept of orienting rows to optimize absorption of photosynthetically active radiation (PAR) and productivity of crops is not new, however, the effects on potato were unknown or unreported prior to this research. Research across six years (2015-20) was conducted to understand the impact of row orientation on PAR absorption potential, potato yield, and economic return near Othello, WA. Clearwater Russet, Payette Russet, Russet Burbank, and Umatilla Russet were each planted between one and four years into rows oriented across four true bearing directions, NS, NWSE, NESW, and EW, and grown using regional standard practices. Each row orientation treatment was replicated once per year and cultivar using a strip-plot design for a total of eight replications. Mid-summer PAR measurements were collected during 2020 for each treatment from the tops and sides of a simulated row. Yield, size profile, US tuber grade and quality, and simulated grower (economic) return were measured and calculated. PAR measurements revealed that plants within NS, NWSE, and NESW rows were more uniformly exposed to the sunlight during the day than those in EW oriented rows. EW rows inherently developed a shady side (north side) and a sunny side (south side). Economic return and yield were generally maximized from rows planted NS, NWSE, and NESW. Planting EW resulted in an economic loss of up to 17.1%, and a reduction in US No. 1, and total yield, and tuber size relative to the other directions. If conditions allow, growers should avoid planting potatoes into EW oriented rows.