The impact on residue amendments on soil functioning

Meeting the food, feed and bioenergy demand for the growing human population has accelerated the use of chemical fertilizers (Kai et al., 2011). The collection of carbon compounds from production land requires re-investment of carbon compounds, in order to maintain soil biodiversity and related processes, however, for practical reasons, local bio-based residues have been applied, often along with chemical fertilizers, as soil additives to improve soil quality and fertility. Yet, there are presently no guiding principles to recommend residue application and usage in a sustainable way, while maximizing their beneficial effect. We aim to deliver a decision support tool (SURE-SUPPORT) to assess the optimal use of residues as soil additives by determining their ecosystem services (e.g. nutritional value, disease suppressiveness, prevention of greenhouse gas emission, detoxicfication effects). As a first step towards the SURE-SUPPORT tool, we will test a range of bio-based residues with a broad spectrum of properties (e.g. low and high C/N ratio, recalcitrance, and potential toxicological effects) to determine their impact on soils (i.e. clay and sandy loam). Microcosm experiments with residue amendment were performed. In parallel, un-amended soils served as reference. Temporal gas flux (CO2, CH4 and N2O) measurements were monitored over two months. Furthermore, the functional diversity of the soil microbial community and population dynamics will be determined using group-specific quantitative PCR assays targeting microorganisms involved in the carbon and nitrogen cycles. Here, we provide an experimental design and preliminary findings on the impact of residue amendment on greenhouse gas emission. Our approaches may be applied and tested under conditions representative for large biomass-producing countries, especially Brazil, Malaysia, and Vietnam.