EFFECTS OF PLANT-POPULATION ON THE PERFORMANCE OF 7 VARIETIES IN THE KLAMATH BASIN OF OREGON

The effects of seed spacing on the performance of seven potato cultiva rs grown at the Klamath Experiment Station in Southern Oregon were eva luated from 1987 through 1991. Seed spacings in 81 cm rows included 17 , 22, and 30 cm, representing the range of local commercial practice. Most varieties evaluated experienced highly significant increases in t uber size as plant populations were decreased. Atlantic was the only v ariety that demonstrated reduced total yield or total yield of US. No. 1's at low populations. Plant population had limited effects on the in cidence of hollow heart and no effect on specific gravity in most vari eties. Optimum seed spacing for fresh market or processing crops range d from 17 cm for Century Russet and Atlantic to 30 cm for Russet Norko tah. Century Russet, Gemchip, and Atlantic produced the highest market able yields. Russet Norkotah experienced the largest yield variability between years. Atlantic and Gemchip were the most consistent in yield of U.S. No.1's over years.