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Agronomy Journal Abstract -

Amino Acid Patterns of Kidney Beans Grown Under Different S and K Regimes1


This article in AJ

  1. Vol. 68 No. 4, p. 668-671
    Received: Oct 18, 1975

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  1. S. M. Hojjati2



The protein of kidney beans (Phaseolus vulgaris L.), an important food crop, is poor in S-containing amino acids and needs improvement. Solution and sand-culture studies have shown that S fertilization increases the concentration of S-containing amino acids in several crops. K application affects protein composition of some crops. The objective of this research was, therefore, to determine the amino-acid concentrations of ‘Naze’ kidney beans and to study the effects of soil-SO42- levels and K2SO4 application on grain yield and amino-acid composition, especially the concentration of methionine.

An area of Xerollic Calciorthid, fine, vermiculitic, chermic soil which had been used previously for a S- fertility study with wheat (Triticum aestivum L. em. Thell.) was used for this trial at Pahlavi University, Shiraz, Iran. The design of the experiment was a split plot with K2SO4, levels as main-plot treatments and the prior S levels constituting the split-plot treatments. (NH4)2HPO4 was applied uniformly at 200 kg/ha. Kidney beans were seeded at the rate of 75 kg/ha.

Proximate protein analyses were made by determining total N content and multiplying by a factor of 6.25. Tryptophan was analyzed colorimetrically and the other amino acids were determined in a Beckman Spinco amino-acid analyzer. Chemical scores reflecting protein quality were calculated by FAO instructions.

Neither K2SO4 fertilization nor the prior S treatments had any effect on yield of dry matter or grain, ratio of grain to total dry matter, or grain-protein concentration. Methionine concentration was positively correlated with soil-SO42- level (r : 0.75; significant at the 1% level.). The first limiting amino acid was methionine, followed by valine and/or isoleucine. Tryptophan was not limiting Regression equations for predicting methionine from soil-SO42- levels and valine and tryptophan from total-protein concentrations are presented.

Sulfur application may increase the methionine concentration of bean protein, but the large amounts of S required and the high costs involved appear to limit the usefulness of this approach for improving protein quality.

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