Soil inorganic nitrogen content in commercial potato fields in New Brunswick

Abstract

Information on inorganic N content in commercial potato fields in Atlantic Canada is limited. Soil inorganic N measurements were collected from 228 commercial potato fields from 1999 to 2001. Soil NO 3 content to 30 cm depth at planting ranged from 2 to 124 kg N ha -1 , and was generally higher for preceding potato, red clover, or hay crops compared to preceding cereal or other crops. Soil NH 4 content to 30 cm depth measured at planting ranged from 3 to 64 kg N ha -1 , indicating that both soil NO 3 and NH 4 need to be measured to assess plant-available soil N content in spring. Soil NO 3 content to 30-cm depth at tuber harvest ranged from 3 to 250 kg N ha -1 , generally increased with increasing fertilizer N application rate, and differed among different potato cultivars. Soil NO 3 content measured to 30-cm depth in spring ranged from 3 to 100% of soil NO 3 at harvest in the preceding fall, indicating that highly variable losses of soil NO 3 from the root zone occur between growing seasons. Key words: Nitrate, ammonium, Solanum tuberosum L.