Rate and timing of nitrogen fertilizer for white potatoes in Virginia

Abstract

Because the precision of N recommendations for potatoes may be improved, the objective was to determine the effect of split N applications on white potatoes in the middle Atlantic region of the United States. Field studies employing rate and timing of N fertilizer were conducted in 1986 and 1987 at Painter, Virginia on white potato (Solanum tuberosum L. cv Superior). Treatments included ammonium nitrate at rates of 0,56,112 and 168 kg N/ha at first cultivation in factorial combination with midbloom-applied N at rates of 0, 56, and 112 kg/ha. Nitrogen treatments were evaluated with an without overhead sprinkler irrigation. Nitrogen applied at 56 kg N/ha at first cultivation increased yields, but N applied at midbloom increased yields only when no N had previously been applied. Tuber yields were higher with than without irrigation, but the yield response pattern to N treatments was not affected by soil moisture. Yield increases may be expected from midbloom N applications at leaf total N critical levels of 58.0 mg/g (dry weight basis) at tuber initiation and 51.6 mg/g (dry weight basis) at midbloom. Routine splitting of N for white potatoes in Virginia is not recommended.