Target-N: Sentinel-2 based nitrogen optimisation in Swedish cereal production

A modelling framework for prediction of site-specific optimal topdressing N rates was developed for winter wheat (Triticum aestivum L.) and malting barley (Hordeum vulgare L.). First, field mean optimal N rate was modelled from different combinations of ancillary data (yield potential, N-uptake in zero-plots, etc.). Second, relative N rate within the field was modelled from remote-sensing based vegetation indices, also relative within the field. Data were collected in ten field trials per crop across south Sweden. In a leave-one-trial-out cross-validation, the topdressing N rates had a mean absolute error of 17 kg N/ha (wheat) and 20 kg N/ha (barley). Satellite-based interactive DSS enable wide adoption of variable rate N fertilization.