Diagnosis of the nitrogen status of wheat at tillering and prognosis for maximal grain yield

From a field experiment in which wheat was supplied with nitrogen fertilizer at 0, 20, 40, 60, 80, 100, 150, 200, or 400 kg ha‐1N, a correlation existed between nitrate concentration in wheat stems at tillering and subsequent grain yield. At early tillering, NO3‐N concentrations around 8,000 μg g‐1 were indicative of sufficient nitrogen in the crop‐soil system for maximum grain yield. Averaging the results of this experiment with those from another seven field experiments, it was concluded that at tillering, the prognostic levels of NO3‐N concentration in stems were: below 4000 μg g‐1 deficient, between 4000 and 6000 μg g‐1 intermediate, between 6000 and 10000 μg g‐1 sufficient and above 10000 excessive for maximum grain yield. These values are applicable in a wide range of water supply conditions and to a number of cereal genotypes.