Nutritive value of potato crude protein as influenced by manuring and amino acid composition

Abstract

Potatoes were grown in pots and fertilised with varying amounts of nitrogen (as nitrate or ammonium sulphate or urea), phosphorus, potassium and cow manure. The largest yield, 451 g D M per pot, was obtained with nitrogen in the form of urea. N-applications and P-and K-deficiency in the soil increased the total-N content, which varied from 1.14-3.07%. Concentrations of nitrate-N (0.001-0.016 %) were negligible. Increasing N-concentrations were associated with decreases in the crude protein of most amino acids including lysine (6.264.17 %), threonine (4.08-2.90 %), methionine (1.98-1.46 %) and tryptophan (1.74-0.86 %). The concentrations of aspartic and glutamic acids (probably mainly present as their amides) increased. Differences in amino acid composition between boiled and unboiled potatoes were negligible. From 70 to 90% of the decrease in concentration of most essential amino acids could be accounted for by changes in N-content of dry matter. Phosphorus and potassium affected the amino acid composition indirectly through their effects on N-content. In rat feeding experiments increasing N-concentrations in potatoes increased the true digestibility of the crude protein from 79 to 91 but decreased the biological value from 82 to 59. The net protein utilisation did also decrease (from 67 to 54). These relationships were linear below 2.2% N in dry matter. Changes were mainly dependent on variations in N-content. Decreases in essential amino acid indices or chemical scores were closely reflected in the results of the feeding experiments. The true amino acid digestibilities were different for individual amino acids and increased with increasing N-concentration in dry matter.

Global food supply: land use efficiency of livestock systems

“…With a yield of 8788 kg per hectare, production of 0.62 kg maize in Germany required 0.71 m 2 year. This Case-specific data were used (see Table 3) c Source: (Gilani et al 2005), except for potatoes (white (Kies and Fox 1972;Eppendorfer et al 1979;Khan et al 1992;Gahlawat and Sehgal 1998), sweet (Ravindran et al 1995)) 0.71 m 2 year could have been used directly to produce human food crops and could yield maximally 0.049 kg HDP ((7019 kg wheat per ha×0.904 DM per kg wheat×125.1 g protein per kg DM wheat × 87 % digestibility / 10,000) × 0.71 m 2 year). In total, the land used to produce 1 kg of eggs and associated chicken meat could have yielded directly 0.27 kg of HDP from human food crops.…”

Nitrogen and Potassium Fertilization Responses of Potato (Solanum tuberosum) cv. Spunta

“…Eppendorfer, Eggum, and Bille (1979) reported that the dry-matter content of potato was directly proportional to the amount of N applied to the soil, and this increase was associated with the protein content (Srikumar and Ockerman 1990). Tuber dry-matter contents at 495 and 660 Kg N ha -1 obtained the greatest values (14% and 22%, respectively) in the first and second growing periods, respectively.…”

Free and Total Amino Acid Composition of Edible Parts of Beans, Kale, Spinach, Cauliflower and Potatoes as Influenced by Nitrogen Fertilisation and Phosphorus and Potassium Deficiency

“…Plant proteins and non-protein N-fractions also contain non-essential amino acids, the amounts of which have a bearing on the protein quality of plants (FAO/WHO 1973). In earlier studies of effects of nutrient supply on amino acid composition and protein quality of vegetables (Eppendorfer 1978;Eppendorfer et al 1979) only results of total amino acids analyses were published. However, for a more detailed understanding of nutrient effects on variations of nitrogen fractions in plants, free amino acids, amides and nitrate have also to be considered.…”