Interrelationship between nitrogen concentration in grain, grain yield and added fertiliser nitrogen in wheat experiments of South‐east England

Abstract

AbstractResults from 20 years of wheat experiments were used to compare responses of grain‐N% and grain yield to increasing amounts of fertiliser‐N. Grain‐N% for both winter and spring wheat increased, mostly linearly, throughout the range, whereas many of the grain yield curves reached a maximum and then declined with further additions of N. Provided curve sections exhibiting dilution effects were excluded, the linear or near‐linear relationship between grain‐N% and fertiliser‐N allowed linear regression models to be fitted. This showed that, over a range of 50‐175 kg N ha−1, an average of 32 kg ha−1 of fertiliser‐N was required for an increase of 0.1% N in grain dry matter of winter wheat or 56 kg N ha−1 for an increase of 1% protein. Results from 3 years of experiments conducted by the Agricultural Development and Advisory Service (ADAS) agreed closely with those obtained from Rothamsted. Using the linear relationship between grain‐N% and fertiliser‐N, curves were plotted of grain yield against grain‐N, adjusted for comparable additions of fertiliser‐N (75, 100, 125, 150 kg ha−1). The curves tended to have sections with rising yield for small applications of N, to exhibit a maximum in a central zone and descending sections for large applications. There was no well‐defined ‚critical level’︁ of grain‐N%, beyond which this and grain yield were inversely related.