Biological Value of Red Beets in Relation to Nitrogen Fertilization

Effects of nitrogen fertilizer and fertilization method on biological value of red beet roots (cv. Boro F₁) were studied in pot experiments conducted in 2005 and 2006 years. Pre-sowing nitrogen fertilizers were either UAN (urea-ammonium nitrate solution) or ENTEC 26 (nitrogen fertilizer containing nitrification inhibitor). For both fertilizers the following methods of application were studied: pre-sowing superficially 90 kg N·ha⁻¹ (S-100%), pre-sowing superficially 67.5 kg N·ha⁻¹ with additional foliar nitrogen application during vegetation (S-75%+F), pre-sowing localized 67.5 kg N·ha⁻¹ (L-75%) and pre-sowing localized 67.5 kg N·ha⁻¹ with additional foliar nitrogen application during vegetation (L-75%+F). In harvested roots the contents of dry matter, sugars, phenols, NO₃⁻, NH₄⁺, N-protein and P, K, Mg and Ca were determined. Type of nitrogen fertilizer had no effect on dry matter, NH₄⁺, N-protein, sugars, phenols, Ca and Mg contents in both years and on K in 2005 year. ENTEC 26 reduced nitrates content, particularly in 2005 year. The effect of fertilization method was not univocal, particularly for NO₃⁻ content. In 2005 the lowest NO₃⁻ content was found in treatment S-100% roots, whereas in 2006 in L-75%. In both years the highest sugars content was observed in L-75% roots, and the lowest N-protein in S-100% roots. In both years the method of fertilization had no effect on dry matter, NH₄⁺ and phenols contents. The effect of fertilization method of on mineral composition was apparent only in 2006 year. It can be concluded that by using the fertilizer with inhibitor of nitrification the biological value of red beets assessed by nitrate content can be improved. The effect of method of fertilizer application on the biological value of red beets is not univocal and may depend on the year of cultivation.