Potential role of “New Agricultural Carbon Credits” (ACC) in sustainable agronomic management

Soil organic matter, in addition to being the basis of physical, chemical, and biological fertility, provides several ecosystem services. Among these, it allows the formation of a stable carbon pool in the soil, mainly represented by substances with slow microbial degradation, contributing to the permanent capture of carbon dioxide from the atmosphere. Various agronomic strategies increase the soil organic matter, such as the burial of crop residues, the use of cover crops, and the organic fertilization. The latter, in recent decades, has been largely replaced by mineral fertilization, which has a more rapid impact on crop productivity. However, if profitability has long guided the choice of farmers, the growing sensitivity of the modern consumer towards a high-quality product with low environmental impact is placing organic fertilization among the useful actions to increase the soil organic matter content. A stimulus towards the use of organic fertilization, due to its potential to permanently accumulate carbon in the soil, is represented by the carbon credit market. The latter bases on voluntary monetized actions, not yet certified, aimed at reducing or eliminating greenhouse gases in the atmosphere, through the implementation or purchase of eco-sustainable practices. A carbon credit represents one ton of CO2e(eq) not emitted or sequestered. Agriculture through carbon sequestration in the soil, can play a leading role in the creation of “New Agricultural Carbon Credits” (ACC). The farmer himself becomes the creator and seller of carbon credits. From this perspective, carbon credits could offset the economic loss caused by a reduction in crop yield that is usually obtained with organic fertilization management. In this context, within the "Podere Fiorentina" Living Lab, ten different agronomic managements based on the combination of organic fertilization, the use of cover crops, and irrigation in a corn-soybean rotation were compared over four years. The objectives of the experimentation were to evaluate, for each of the ten possible managements tested, the soil organic carbon accumulation, corn and soybean grain yield, and the impact of the carbon credit system application on the economic sustainability of each management. Results indicate that, for some of the managements, carbon credits can represent an interesting tool to stimulate the adoption of agronomic practices aimed at the soil organic carbon accumulation.