The effects of variable nitrogen fertilization on amino acid content in sweet potato tubers (Ipomoea batatas L. [Lam.]) cultivated in central and eastern Europe

Abstract

BACKGROUND: The weakest link in the whole cycle of chemical quality testing of sweet potato tubers for both food and feed purposes, where the main determinant of their nutritional value is the level of protein and its nutritional value, is the effect of nitrogen fertilization. Therefore, the aim of the study was to determine the effect of differentiated nitrogen fertilization on protein content and its amino acid composition, biological value, and the possibility of modification of these features. RESULTS: Changes in total nitrogen content in sweet potato tubers were accompanied by changes in amino acid composition of protein. The consequence of intensified nitrogen fertilization was a decrease in the sum of exogenous amino acids and sum of endogenous amino acids. The amino acid limiting the biological value of sweet potato protein was mainly lysine, followed by arginine and methionine. The ratio of essential to total amino acids indicated high usefulness of sweet potato tubers in human nutrition and their high nutritional value. CONCLUSION: The consequence of nitrogen fertilization was a decrease in the sum of exogenous amino acids and the sum of endogenous amino acids. Fertilization of sweet potato with a nitrogen dose of 100 kg ha−1, due to the content of crude and true protein, turned out to be beneficial and sufficient under the conditions in central–eastern Europe. © 2020 Society of Chemical Industry. © 2020 Society of Chemical Industry