Published online by Cambridge University Press: 27 March 2009
The analysis of two experiments involving the response of bread-making wheat to application of nitrogenous fertilizer is discussed. It is shown that a step function is required to determine the amount of applied N which optimizes the profit to be obtained from the crop. Varieties varied in their yield response to N and in the amount of applied N at which the ‘step’ took place and it is argued that trials of varieties at a common rate of N application or the reporting of results which are averaged over a number of rates cannot lead to very precise recommendations for growers.