Detailed case study: assess impact of less livestock and change in diet on soil organic carbon

In this study, the impact of an adjustment in the composition of cattle feed on the soil organic carbon stocks in Flanders (Belgium) was investigated. Silage maize is the most common fodder crop, and even the most common crop cultivated in Flanders. However, silage maize does not have a high contribution to the SOC storage in arable soils compared to some other crops, such as cereals and fodder legumes. In this study, we have investigated the impact on SOC stocks of replacing silage maize by winter barley, with straw residues removed after harvest, on 10% of the parcels where it is currently cultivated. The impact of the shift in fodder crops was simulated with a Roth-C based model. The Belgian Soil Organic Carbon Calculator (BeSOCC) integrates the Roth-C model, with an approach for the initialisation and the calculation of carbon inputs by crops and fertilization developed specifically for Belgium, Flanders that builds further on earlier work for developing a digital decision support tool for farmers to simulate the evolution of the SOC in arable land. The scenario was compared with a business-as-usual (BAU) scenario. The BAU scenario was developed based on the management data of 5 years (2018-2022). Due to missing crop and fertilization data, simulations could be performed for 52.3% of the arable fields. The simulations were performed at parcel-level and afterwards aggregated to NUTS3 level. The results indicate that an increase of the SOC storage will occur in all NUTS3 areas if there is a shift in the fodder crops. This increase is on average 0.013 Mg C. ha-1. Yr-1 and ranges between 0.003 and 0.025 Mg C. ha-1. Yr-1 .