Protein nutritive value of potatoes is improved by fertilization with nitrogen

Dry matter yields and total-N percentages of potato tubers have been reported to increase with increasing application of fertilizers to potato plants. The concentrations of most of the amino acids found, have been reported to decrease, when calculated on the basis of grams of amino acid per 16 g total-N, which assumes that protein and amino acid contents are proportional to nitrogen content. Recalculation on a dry matter or absolute basis, however, shows increases of amino acid content with increasing nitrogen content of the sample. Similar effects are shown for EAAI, chemical scores, and feeding experiments.