Model analysis of the significant drop in protein content in Danish grain crops from 1990-2015

Abstract

Abstract The content of crude protein in grain decreased 2.4–2.9 percentage points (dry matter basis) in Denmark between 1990 and 2015. The aim of this model analysis was to quantify to which extent the reduced crude protein content in winter wheat and spring barley was caused by a) changed N-response in new varieties, b) changed fertilizer norms, field management and N-deposition, c) decreased N-mineralization due to structural changes in Danish farming, and d) warmer and wetter weather. The analysis was carried out using the plant-soil-atmosphere model DAISY. It was possible to simulate most of the observed change in protein content. For winter wheat, changes in fertilizer regulations driven by environmental concerns and accompanied by a drop in aerial deposition of nitrogen explained between 50 and 70 % of the total simulated decline in crude protein content. The changed N-response of new varieties explained 15–20 %. For spring barley, the changed N-response accounted for 45–60 % of the observed change under mineral fertilization and 40–45 % in scenarios receiving slurry. Warmer and wetter weather accounted for around 20 % of the change for both crops. On the more clayey soils, reduced mineralisation influenced the protein content, and this effect was probably underestimated in the study.