Abstract

Beetroot has many positive effects on human health but can also accumulate considerable amounts of harmful nitrate and oxalate. A two-year open field trial was carried out to evaluate the influence of nitrogen fertilization on the content of different N compounds and oxalate in beetroot. Three nitrogen rates were applied: 0, 75 and 150 kg of N ha^-1. Dry matter, oxalate, nitrate N and reduced N were determined in storage root, leaf lamina and leaf petiole. Different parts of beetroot differed significantly in the content of analyzed substances. Leaf lamina had the highest reduced N and oxalate and the lowest nitrate. Storage root usually had the highest nitrate and the lowest oxalate while the reduced N was approximately half of that found in leaf laminas. Contents in leaf petiole were between the leaf lamina and storage root. It can be concluded that different parts of beetroot differ significantly in metabolic activity, with leaf lamina being the most active and storage root the least active part. Nitrogen fertilization had a significant influence on the content of nitrate N and reduced N in all beetroot parts whereas, the contents of dry matter and oxalic acid were, in most cases, not influenced by N rates.

Key words: Fertilization, beetroot, storage root, leaf lamina, leaf petiole, nitrogen, oxalate.