COPPER AND ZINC NUTRITION OF RUSSET BURBANK POTATOES GROWN ON PRINCE EDWARD ISLAND

Abstract

Field experiments were conducted on potatoes (Solanum tuberosum L.) at two locations in P.E.I. to determine the response to soil- and foliar-applied Cu and Zn on tuber yield and leaf tissue nutrient concentration over a period of 3 yr. Foliar applications of 0.5–2 kg Cu ha−1 applied 1–2 wk prebloom reduced total tuber yield, number of tubers over 55 mm in diameter, average tuber weight, and specific gravity. The mean potato yield of tubers over 55 mm from the foliar-applied Cu treatments was less than the soil applied Cu by 4.5, 0.74, and 7.5 t ha−1 for 1985, 1986, and 1987, respectively. The toxic concentrations of Cu in potato leaves ranged from 63 to 139 μg g−1. Soil-applied Cu increased tissue Cu in the first sampling but had no effect in the second sampling. Foliar applications of Zn at 1–2 kg ha−1 reduced total tuber yield, tuber yield and tuber count over 55 mm, and specific gravity. The toxic concentrations of Zn in potato leaves ranged from 97 to 224 μg g−1. For the first sampling, the leaf tissue Zn concentrations ranged from 21 to 30 μg g−1 for the control and 27 to 70 μg g−1 for soil-applied Zn treatment. There was no difference in the Zn concentration between these two treatments for the second sampling. Copper and Zn concentrations as low as 7 and 21 μg g−1, respectively, in potato leaves were not related to deficiency of these nutrients, based on tuber yields. Soil applications of Cu or Zn would appear preferable to foliar sprays, which may cause phytotoxicity, as a means of increasing plant Cu or Zn content where a deficiency is suspected.Key words: Solanum tuberosum L., tuber yield, leaf copper, leaf zinc, Podzolic soil, potato