Effects of S, N and P on amino acid composition of field beans (Vidafabd) and responses of the biological value of the seed protein to S‐amino acid content

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Abstract
In pot experiments dry matter yield of seed of Vicia faba was increased by increasing application of S at all N‐ and P‐levels and, by P at all S‐ and N‐levels. Significant interactions were found for PxN (0.1%) and SxP (1%). N‐concentrations generally increased with S‐additions, but decreased with large applications of N and P. Significant interactions were found for PxN fl‐1%) and SxP (5%) with regard to N concentration. Maximum increases in cystine and methionine contents from S‐application were respectively 39.1 and 13.7% expressed as % of dry matter and 37.9 and 12.3% expressed as g/16 g N. Highly significant correlation coefficients were obtained between concentrations (g/16 gN) ofa number of protein am/no acids in seeds and total‐N content. In a feeding trial with rats, the biological value of non‐S treated seed was 40.8 and increased to about 60 in seed from S‐treatments Addition of synthetic cystine and methionine to seed from the non‐S treatment could not entirely substitute these acids present in the protein of seed from S‐treatments with regard to effects on the biological value of seed protein.