The content and quality of protein in winter wheat grains depending on sulphur fertilization

Abstract

On soils lacking in water-soluble sulphur, the sulphur fertilization of winter wheat, in general, increases the yields. There are not sufficient investigations about the influence of sulphur on the quality of yield. The objective of this work was to investigate the content and quality of protein in wheat grain depending on sulphur fertilization. The present study relies on field trials conducted on two different soils during 2004–2009. Sulphur was applied with NS-fertilizer Axan or Axan Super at the rate of S 10 or 13.6 kg ha⁻¹ accompanied by a nitrogen background of N 100 kg ha⁻¹. The rates of N- and NS-fertilizers were divided and applied at the beginning and at the end of tillering. At harvest, the grain samples from trial variants in four replications were taken, and the contents of crude protein, wet gluten, amino acids (lysine, threonine, cysteine, methionine) and gluten index in wheat grain were determined. Besides, the contents of amino acids were recalculated on their concentrations in protein. The protein and wet gluten contents in grain varied significantly depending on weather conditions of the trial years. On break-stony soil, sulphur increased the yield by 1.16 t ha⁻¹ on average, i.e. by 21.7%. With increasing yields the protein and wet gluten concentrations in grain decreased. Under the influence of sulphur, the gluten index increased significantly – from 58 to 74, i.e. by 27.6%. In 2004 and 2005, sulphur increased the cysteine and methionine content in wheat grain. Although sulphur application in many cases decreased the protein and wet gluten contents in wheat grain, it improved the biological quality of protein because the concentrations of above-mentioned amino acids recalculated on their concentrations in protein increased significantly. The sulphur application in pseudopodzolic soil had a weaker effect on the grain quality than in break-stony soil.

Keywords:

• Crude protein
• cysteine
• gluten index
• grain yield
• lysine
• methionine
• threonine
• Triticum aestivum
• wet gluten

Acknowledgements

Financial support from the Estonian Ministry of Agriculture through the project ‘Improving the food and feed quality of cereals, grain legumes and oil crops by implementing economically effective and environmentally sustainable agrotechnical methods’ (2006–2010) is much appreciated. We thank Mr Jaanus Rebane and Mrs Ann Akk for the description of analysis methods. We thank also the staff of the plant production laboratory of the Agricultural Research Centre for their accurate analytical work. The authors are grateful to Mrs Helena Pärenson for her linguistic consultations.