Agro Fossil Free - Impacts of agronomic measures on crop, soil, and environmental indicators: A review and synthesis of meta-analysis

Opis ogólny

Sustainable agricultural management implies optimization of resources for crop production while minimizing adverse impacts on the environment. This requires a better understanding of the synergies and trade-offs of agronomic management while accounting for the controlling effects of site-specific factors (covariates). We systematically evaluated 113 meta-analytical studies assessing impacts of crop management measures (rotation, cover cropping, residue retention), soil and water measures (irrigation, tillage), soil amendments (enhanced efficiency, biochar), fertilizer use (organic, mineral, combined organic-mineral) and “4R'” fertilizer strategies (right source, rate, timing, placement) on sustainability indicators. These indicators include crop yield, crop N and P (content, uptake, and use efficiency), soil quality indicators (soil organic C, N and P contents, compaction), soil emissions of ammonia (NH3) and greenhouse gases (CO2, N2O), and nutrient losses to water (N and P surplus or leaching). Nutrient management, including 4R practices as well as enhanced efficiency amendments, had the largest impact, increasing crop yields and N uptake while reducing N2O and NH3 emissions as well as N surplus, whereas effects on CO2 emissions were variable. Although all measures positively impacted soil C, the largest effect was due to biochar, followed by organic fertilizer input. Biochar positively impacted crop yield, diminished N2O and NH3 emissions as well as N surplus, and increased CO2 emissions. Within crop management, only cover cropping had a significant positive effect on crop yield, while both cover crops and rotation slightly enhanced N uptake and the sequestration of C and N in soil, thus reducing N2O emissions and N surplus. Minimal tillage practices generally increased SOC, while results for crop yield, N surplus and N2O emissions were variable. Site-specific factors had substantial impacts on the evaluated impacts of measures, most importantly climate, crop type, soil texture, soil pH, soil organic C, N dose, and experimental duration. Considering the variation among meta-analytical protocols followed, we recommend that field studies and meta-analytical work adhere to harmonized guidelines with respect to the reporting of site-level data, experimental design, and the statistical procedures used. This will ensure data comparability between studies, improve the quality of meta-analysis results, and give better insights into currently uncertain or unknown impacts of agronomic measures.