Impact of EU Policies on NUE, Carbon and N₂O Footprint: Do EU Policies mitigate GHGs Emissions?

We investigated the impact of soil organic carbon (SOC) and fertilizer use on NUE, Carbon footprint, and N₂O footprint from agrosystems within the context of EU Common Agricultural Policy (CAP) and Green Deal (EUGD) for sustainable agriculture, GHG mitigation, and fertilizer use reduction.

We targeted 27 fields from the Imathia Plains in Greece, including cotton, maize, and tomato crops, and collected farmer and soil data. The collected data were used within the Cool Farm Alliance Tool to calculate GHG emissions, N₂O emissions, and NUE. Six scenario cases were studied: Scenario 1 used data collected from farmers, with original fertilizer use and current soil organic matter (SOM); Scenario 2 increased SOM by 20%; Scenario 3 involved the application of 20 ton/ha of fully aerobic compost containing 1% total N, resulting in an additional 200 kg N/ha in the soil; Scenario 4 reduced the use of fertilizers by 20%; Scenario 5 reduced fertilizers use by 20% and increased SOM by 20%; and Scenario 6 combined a 20% reduction in fertilizers with the co-application of 20 ton/ha of fully aerobic compost. Compost was added to Scenarios 3 and 6 to evaluate its impact and alignment with CAP and EUGD goals. We assumed that crop yield would be the same for all the scenarios.

The results showed that Scenarios 3 and 6 had NUE values between 30% and 80%. This suggests a low risk of soil mining or N losses. However, these scenarios also had significantly higher GHG (CO2-eqv) and N₂O kg emissions compared to scenarios without compost application. Additionally, increasing SOC by 20% (Scenarios 2 and 5) did not significantly impact NUE and GHG emissions for most crops.

The higher GHG and N₂O emissions in some scenarios may be due to the mechanical processes and fuel required for compost application. Additionally, the decomposition of compost can also produce GHGs, such as methane and carbon dioxide. It is important to consider that carbon fuels microbial activity in the soil, including the production of N₂O. While the addition of organic matter can improve soil health and increase NUE, it is necessary to carefully evaluate the potential impacts on GHG and N₂O emissions and identify strategies to mitigate these emissions if needed.

Based on the results of our research, one question that arises is whether the benefits of improved NUE and reduced risk of soil mining or high N losses are offset by the higher GHG and N₂O emissions in Scenarios 3 and 6. Trade-offs between different factors may need to be considered for sustainable and effective soil management. More research may be needed to understand the higher GHG and N₂O emissions in Scenarios 3 and 6 and identify ways to mitigate these emissions while improving NUE.

Funding: The MSc research work by Korina Koukoutsi was partly supported by the Hellenic Foundation for Research and Innovation (HFRI) Post-Doctoral Grant #1053 awarded to Principal Investigator Dr Georgios Giannopoulos. This project was co-implemented with industrial partner Corteva Agriscience Hellas SA.