[Effects of long-term rotation on the nutritional quality of wheat grain protein on dryland of Loess Plateau, Northwest China].

A long-term experiment was conducted on the dryland of Loess Plateau to study the effects of three typical rotation systems, including wheat-sainfoin rotation, wheat-pea rotation, and wheat-maize rotation, on the nutritional quality of wheat grain protein. Rotation system and the cropping years of rotated plants affected the nutritional quality of wheat grain protein in varying degrees. As compared with continuous wheat cropping, wheat-sainfoin rotation made the nutritional quality of wheat grain protein relatively stable, and the essential amino acid content, amino acid score, amino acid ratio coefficient, chemical score, and amino acid index of the protein all relatively high, being able to be adopted as a cropping system to product high quality protein wheat in Loess Plateau. Under wheat-pea rotation, the nutritional quality of wheat grain protein after 1-year pea cropping was relatively high, but the essential amino acid content of wheat grain protein after 2-year pea cropping was relatively low, and several essential amino acid scores and chemical score of the grain protein were lower than those under continuous wheat cropping. Furthermore, the essential amino acid index was 12.2% lower than that under continuous wheat cropping. Therefore, wheat-pea rotation showed a relatively low nutritional quality of wheat grain protein. Under wheat-maize rotation, the nutritional quality of wheat grain protein was also relatively stable, but the crude protein and essential amino acid contents and amino acid balance level were lower than those under continuous wheat cropping.