YIELDS AND PROTEIN TRENDS OF SPRING WHEAT (Triticum aestivum L.) ON THE CANADIAN PRAIRIES, 1961–1982

Mathematical models of hard red spring wheat (Triticum aestivum L.) were used to account for effects of weather on annual variations in yield and protein content on the Canadian prairies. When weather effects were calculated, other relatively slow-changing trends became much clearer. Results indicate that yields in the three major soil zones have increased an average of 806 kg ha−1, while protein contents have decreased (1.0% from 1961 to 1982). Both trends show the largest change at the beginning of the period (1961) with a levelling off at the end (1982). There seems to be an inverse relationship between yield and protein, with technology contributing to yield increases and at the same time decreasing protein content by dilution although this was not conclusively proved. Decreases in soil organic matter or other soil factors may be contributing to the protein decline but these factors were not required to explain the observed patterns in yield and percent protein. The results indicated that the potential to produce high protein wheats has decreased during the period 1961–1982.Key words: Nonlinear fitting, physical model, technology effects, protein dilution