Effect of Long-Term Organic and Mineral Fertilization on the Yield and Quality of Red Beet (Beta vulgaris L.)

In 2003-2004, an experiment was carried out with two cultivars of red beet using the experimental plots of a long-term static fertilization experiment that was begun in 1922 in the Experimental Field of the Institute of Vegetable Crops in Skierniewice. Under assessment was the response of red beet plants to longterm organic, mineral, and organic-mineral fertilization applied at different rates. The highest marketable yield, of all the fertilization combinations, was obtained in each year of the experiment from the each year treatment with manure alone at 60 t·ha^-1. However, the level of red pigments in beet roots from this treatment was low, while that of yellow pigments, and also of nitrates, was high. Fertilization with manure at 60 t·ha^-1 in combination with mineral nitrogen fertilization at 60 kg N·ha^-1 resulted in a lower marketable yield compared to the treatment with manure only. The roots from the combined treatment, like those from the treatment with manure alone at 60 t·ha^-1, had a low ratio of betanine to vulgaxanthine, and the highest nitrate content of all the fertilization combinations. At lower levels of fertilization with manure (20 and 40 t·ha^-1), the additional fertilization with mineral nitrogen increased the marketable yield of red beet roots, but it reduced betanine content in 2003, and increased the level of nitrates in both years, in comparison with the corresponding treatments with manure only. Relatively high marketable yields of well-coloured roots with a high betanine content and a low vulgaxanthine content, and a low level of nitrates, were obtained from the treatment with mineral fertilizers applied at the lowest rates (N - 60, P₂O₅ - 30, K₂O - 70 kg·ha^-1). However, as the application rates of these fertilizers increased, the marketable yield of beet roots and their betanine content decreased. At the same time, the level of nitrates in the roots of both cultivars increased. The lowest marketable yields, but of well-coloured beet roots with a low nitrate content were obtained from the zero-fertilization control plots and from the treatment with manure alone at 20 t·ha^-1.