Relationships of wheat quality with climate and nitrogen application in regions of England (1974-1993)

Region × year means for crude protein concentration (CP) and Hagberg falling number (HFN) from the Home Grown Cereals Authority (HGCA) surveys were modelled using mean daily temperature, rainfall and nitrogen application. A model accounting for 78.6% of the variation in CP incorporated positive coefficients for mean daily temperature (25 June to 15 July), nitrogen applied to the crop, and early summer rainfall (28 May to 8 July), and a negative coefficient for spring rainfall (5 March - 27 May). For CP there was no statistical evidence that fitting one regression for all regions was significantly worse than fitting individual lines for each of the 10 regions. A model describing 67.1% of the variation in HFN incorporated a negative coefficient for August rainfall and positive coefficients for mean June temperature, mean August temperature and nitrogen applied to the crop. There was statistical evidence that fitting separate lines for certain regions was justified.