Impacts of Agronomic Measures on Crop, Soil and Environmental Indicators in European Agriculture: A Review of Meta-Analyses

Keywords: agronomic measures, environmental indicators, crop production, nitrogen use efficiency, soil organic carbon, nitrogen surplus.

Food systems face multiple challenges globally, including the production of sufficient crops of high nutritional quality while reducing the environmental impacts of this production, especially in the face of climate change and biodiversity loss. The use of meta-analysis in ecology and natural sciences has developed remarkably fast in the past decade. Given this, numerous meta-analytical studies have been done to unravel the averaged impact of agronomic measures on crop yield, soil organic matter levels, and nutrient losses. As it becomes increasingly important to control the fate of nutrients in cropping systems, measures that synchronise nutrient supply and crop demand are key to optimising trade-offs amongst yield, profit, and environmental protection.

In our study we build upon an agronomic dataset synthesized from published meta-analyses on long-term field experiments to assess the impact of fertiliser strategies for different site properties in a decision support framework (DSF). The DSF in our study focuses on three main indicators related to agronomy, soil quality and environmental impacts – specifically crop yield, soil organic carbon (SOC) content, and nitrogen surplus, given their dependency on site properties.

This analysis focuses on nutrient management strategies, including mineral and organic fertilisation, the right application of fertilisers (e.g. 4R strategies), and the use of enhanced efficiency fertilisers. The impacts of measures were evaluated by comparing expected changes in those indicators to their current levels and distance to existing target levels (crop yield and SOC) and critical levels (nitrogen losses). We used a spatially-explicit upscaling technique to map outcomes in the EU-27 region. The main objectives were to (i) assess how the effect of a measure varies for different indicators and under local conditions, (ii) evaluate the performance of measures at meeting multiple agronomic objectives, and (iii) map the expected impact of measures in various European regions to identify trade-offs and synergies.

Using enhanced efficiency fertiliser, right fertiliser rate, and right fertiliser timing were the most effective measures for meeting crop yield, SOC, and N surplus targets in Europe, both individually as well as when applied in combination. The right fertiliser placement, combining organic and mineral fertiliser, and using organic material were generally less effective. Our results indicate that adapting fertiliser measures in Europe can significantly increase in the level of yield and N surplus targets met, but overall increases for SOC were minimal. Our analysis investigates how management recommendations vary under different site properties, illustrating that this is a key component for further research.