Comparison of nitrogen fertilisation recommendations of West European Countries

Abstract

Nitrogen (N) budgets at farm level are influenced by N fertilisation recommendations. In this study, we reviewed and analysed the underlying principles and methods of N fertilisation recommendations in ten West European countries, to identify similarities and differences, and develop suggestions for reconsideration and improvement. An analysis of national official documents on N fertilisation recommendations revealed that there were three main categories of calculation methods: (i) ‘N mass balances’ (France, Italy, Spain), (ii) ‘Corrected standards’ (Germany, Netherlands, Switzerland, Luxembourg), and (iii) ‘Pre‐parameterised calculations’, which rely on a soil N supply typology (United Kingdom, Ireland, Belgium). In total 16 variables were identified in the calculation methods. The more complex methods use 10 (Italy, France), while the simplest only rely on 3 (Luxembourg). The most common variables include the availability of N in manure, the N uptake by a crop, and the N released by crop residues. Few countries explicitly consider N losses to ground and surface waters or to the atmosphere in the calculation methods. In some countries, the N fertilisation recommendation has a voluntary status, in other countries a legal one (caps on maximum allowable N rates). We compared the N fertiliser recommendations for a wheat crop grown on a farm with livestock, and for a farm with a diverse arable crop rotation without livestock. Across the 10 countries, large differences in the N fertilisation calculation methods and resulting N recommendations existed for the two management scenarios, ranging from almost no fertilisation to 135 kg N ha‐1, and from 111 to 210 kg N ha‐1, respectively. The differences were not accounted for by the complexity of the equations used, but rather resulted from contrasting reference values for N availability in manure, N uptake by crop and N leaching.However, the study concluded that standardisation of the method to calculate N fertilisation recommendations is likely to be counterproductive as there are no objective reasons to favour one method more than the others. Nonetheless, improvements in N use efficiency are necessary. Farm scale mass balance, combined with parameters such as minimum residual soil mineral N test at harvest was suggested as being an important consideration.This article is protected by copyright. All rights reserved.

Stocktake study of current fertilisation recommendations across Europe and discussion towards a more harmonised approach

“…The local adaptation needed at the farm and field scale for efficient use of resources should be considered. Current differences in fertiliser recommendations may result in, for example, an optimal N rate in some countries being substantially higher for the same crop and the same harvest than in other countries (Jordan-Meille et al, 2022). To establish such circumstances and investigate plausible reasons and environmental and economic consequences are of considerable interest.…”