Soil nitrogen variability in relation to seasonal nitrogen cycling and accumulation of nitrogenous components in starch processing potatoes

Abstract

Seasonal dynamics of total soil nitrogen, ammonium and nitrate ions contents were evaluated for a processing potato field experiment conducted on three sites with different altitudes. Fertilization levels of 100 and 200 kg N ha−1 applied before potato crop planting were compared. Content of soil ammonium and nitrate ions ranged from 1.5 to 149 mg kg−1 and from 3.0 to 108 mg kg−1 on soil dry matter basis, respectively and showed strong seasonal dynamics with a rapid increase of the content during June and subsequent fall down to initial values. The nitrogen fertilization level had minimal effect on seasonal dynamic of total soil nitrogen, ammonium and nitrate ions contents. The higher fertilization level significantly increased crude protein content in potato tubers and yield of crude protein per area unit. The factors of starch content in potato tubers and yield per area unit were affected negatively by the higher dose of nitrogen fertilization. It could be concluded that the dose of 100 kg N ha−1 is sufficient for production of potato tubers with high content of both crude protein and starch, especially in production areas with higher altitude. The dose of 200 N is justifiable only in production areas with lower altitude (below 400 m a.s.l.) that are not so suitable for accumulation of crude protein and starch in potato tubers.