Application of ramial wood chips in arable fields to improve carbon storage in the soil and soil quality

Introduction and objectives Beside fertile soils and slopes, South-East Flanders is characterised by numerous sunken lanes and hedgerows connecting natural elements in a landscape dominated by farmland. These woody elements are valuable for the environment, but may also be valuable for agriculture. To maintain a sustainable use of the adherent fields, regular maintenance of the hedgerows is needed. The wood waste resulting from this maintenance is often used as biofuel, but the small fractions are not suited for this. In this study we applied these fractions on arable fields in order to investigate the effects on crop growth and soil quality parameters including soil organic matter content, infiltration capacity and erosion risk. Materials and methods In autumn 2016, ramial wood chips were applied and incorporated superficially on one part of 4 fields, combined with different cover crops and no-tillage practice. The rest of these fields was conventionally managed according to the normal farmers practices. Soil samples were taken at the start of the project, in order to determine soil organic C, pH and nutrients, during the season, in order to follow up mineral N availability and at the end of the season, to determine N residues. The applied wood chips were analysed and based on the C:N ratio the decomposable/resistant plant material (DPM/RPM) ratio was estimated. Simulations were made with the Roth-C model to predict soil organic C evolution. Historical data of each field were used to calibrate the model and previous crop rotations were extrapolated for the next 30 years to estimate future C evolution. The use of wood chips was thereby compared to the application of household waste compost and solid manure. Finally, during the growing season observations were made of soil infiltration capacity, erosion, earthworm populations and crop development. Results and conclusions The first measurements of soil mineral N did not show consistent differences related to the application of ramial wood chips. More soil analyses and measurements will be executed during the 2017 and 2018 growing seasons. Simulations with the Roth C model indicated that the soil carbon storage would increase substantially more after the application of ramial wood chips compared to the application of equal amounts of solid manure or household waste compost.