Investigating two solutions to balance revenues and N surplus in Swiss winter wheat

Abstract

CONTEXTReducing N surplus from agriculture without compromising yield and quality requires economically and ecologically viable solutions. OBJECTIVEBased on field data, we investigated a technical and market-based solution to balance the economic and environmental performance of nitrogen (N) fertilizer application in winter wheat in Switzerland. METHODSThe technical solution, i.e. variable rate (VR) technology, was compared to the standard uniform fertilizer application (ST) in terms of revenues and N balance over seven site-years between 2018 and 2020. The potential of a market-based solution to align revenues and N surplus was investigated based on the relationship between two indicators: the economic optimum (EO) of the revenues and the balanced N supply (BNS). The EO was estimated using a production function approach. The BNS was empirically defined as the point at which the N surplus estimated from total N input (N fertilizer + soil N supply) reaches a limit value of 30 kg N ha−1. RESULTS AND CONCLUSIONSOn average, the revenues of VR were about 4% higher than in ST. The N surplus was, on average, 32% (21 kg N ha−1) lower in VR compared with ST due to a 13% reduction in N inputs with no significant differences in yield. Despite the differences across years and fields, VR appeared to be reducing N surplus without losses in revenues in 5 out of 7 site-years. The revenue curve reached an EO at total N input of 205, 249 and 246 kg N ha−1, in the years 2018, 2019, and 2020, respectively. The BNS was calculated at 220, 195, and 178 kg N ha−1 N inputs for the years 2018, 2019, and 2020, respectively. The results show that a price increase of up to 5.4 times the current fertilizer price through taxes would be necessary in order to reduce the N surplus to an environmentally friendly level. Such an increase would hardly be politically feasible. SIGNIFICANCEThe reported data showed that VR technology appears as a viable solution for producing lower N surplus at comparable revenue levels, thereby making it an option for small- to medium-scale winter wheat production in Switzerland. The environmental benefit could encourage the financial support of technologies for precise N management, which are often too expensive for these systems. Future research should verify or extend the numeric values found in this study.