A modified delta yield approach for estimation of economic optimal nitrogen rate (EONR) for wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.)

Abstract

A Swedish field trial database was mined for information on economic optimal nitrogen rate (EONR). A total of 100 trials with wheat (Triticum aestivum L.) and 47 trials with barley (Hordeum vulgare L.) were used to parameterize prediction models for EONR based on yields in plots with no nitrogen (N) fertilisation, intended to reflect N mineralisation, and yields in plots with a high N rate, aimed as a proxy variable for yield potential, i.e. a modification of the delta yield (ΔY) approach. When the prediction models were applied to new sites and years, predictions had mean absolute error (MAE) = 10 kg N ha-1 for wheat and = 9 kg N ha-1 for barley. Performing modified ΔY experiments can complement current N fertilisation trials with many rates, in order to improve the spatial representation of EONR estimations. Moreover, ΔY experiments can potentially be used for in-season EONR estimation, in which case the accuracy of the EONR predictions depends also on the uncertainty in yield predictions made at the time of supplementary fertilisation.