Mitigating Agricultural Greenhouse Gas Emissions by improved pH management of soils

Climate forcing by crop production is dominated by N2O emissions. Although emissions can be marginally reduced by “good agronomic practice”, we need more targeted approaches to make progress. For that, MAGGE-pH concentrates on the microbial processes responsible for production and consumption of N2O in soils. Our point of departure is the emerging understanding of how soil pH perversively controls the N2O/(N2O+N2) product ratio of denitrification. Since denitrification is the dominant source of N2O, this indicates that N2O emissions from cultivated soils can be reduced substantially by increasing the pH of moderately acidic soils beyond that needed to secure adequate crop growth. This necessitates policy instruments to secure effective implementation, and MAGGE-pH will deliver socio-economic analyses to identify such instruments.

The evidence for the pH effect on N2O emissions stems almost exclusively from laboratory experiments. Now we need stringent testing of different liming strategies under realistic field conditions. This will be the core activity in MAGGE-pH and generate emission factors for a range of N fertilizers / manure / urine / biochar applications explicit for soil pH. We will also explore the use of non-calcareous rock powders as a replacement for traditional limes (carbonates). This is highly relevant, because CO2 emissions from carbonates can negate their potential GHG reducing effect. MAGGE-pH will also explore novel approaches to manage soil pH via fertilizers and manure, in order to reduce both N2O emission and NH3 volatilization. Thus, the project adds some "blue sky” research to the core objectives and puts it to the critically evaluation by a broad European consortium consisting of researchers, fertilizer companies and practitioners.

Norwegian University of Life Sciences, Norway
Dr. Peter Dörsch

Project partners
National University of Ireland, Galway, Ireland
Teagasc, Ireland
Aarhus University, Denmark
Thuenen Institute, Germany
Swedish University of Agricultural Sciences, Sweden University of Helsinki, Finland
Institut National de Recherche en Agronomie (INRA), France
University of Otago, New Zealand
Natural Environment Research Council, United Kingdom

Total requested funding
2,269,000 €

Project duration
36 months




The project held its annual meeting at INRAE, Clermont-Ferrand, France, 24-25.02.2020, and discussed the results of the field and laboratory experiments. The soils range from a Swedish peat through clays and loams to a Danish coarse sand, with either perennial grass leys or annual cereals. Overall, we confirm our hypothesis that raising soil pH reduces nitrous oxide (N2O) emission when soils 2O suppressing effect depends on whether denitrification is induced. Hence, the liming effect has to be evaluated in connection with other factors regulating soil N turnover. Liming scenarios for German soils suggested that the N2O saving effect of liming could be offset by CO2 emissions during production and use of agricultural lime in many situations, but more data are needed to test this effect on a per-tonne-of-product basis.