This demo is considered to be at TRL 7-9 and has been set up at field scale. The trial is running for three years. During the first year, maize is tested. The second and the third year are spinach and early potatoes, respectively. The tested recycling-derived fertilizers are ammonium sulphate, ammonium nitrate, pig urine, pig slurry, and liquid fraction of digestate.
This demo solution is linked to Nutri2Cycle research line 4 (RL-4: Biobased fertilisers (N, P) and soil enhancers (OC) from agro-residues) and is one of the shortlist priority solutions i.e. sub-research line 4 (Substituting external mineral nutrient input from synthetic fertilisers by recycled organic-based fertilizers in arable farming).
In Flanders, livestock production generates large surpluses of on-farm nitrogen (N) and phosphorus (P). High P content and uncertainty on N release from animal manure have led to an imposed legal limitation on N and P application rates from animal manure. Since Flemish soils are P-rich, the P has become the limiting factor in manure application, thereby also limiting maximum N application from animal manure. This creates a paradoxical situation where vast quantities of manure are processed or exported out of Flanders while tons of synthetic mineral N-fertilizers are used for crop production. The use of manure recycling derived fertilizers (RDFs) with predictable N release and low P content can counter this situation. At the moment, however, the RDFs derived from animal manure are categorized as animal manure and as such, need to comply with the same legal application constraints. The main goal of the trial is to establish a clear relationship between the amount of N applied by RDF and dry matter production for each applied RDF. The trials are planned to run for three years. During the first year, maize is tested. The second and the third year are spinach and early potatoes, respectively. The tested recycling-derived fertilizers are ammonium sulphate, ammonium nitrate, pig urine, pig slurry, and liquid fraction of digestate.
This trial provides a great overview of how these products can help to close CNP loops by nutrient recovery from animal manure. The most important function of any fertilizer is supplying the crop with sufficient nutrients. N is the most important nutrient for crops, and its availability is closely linked with crop yield. A mismatch between N supply and crop demand, on the other hand, also leads to nitrogen losses to the environment. Therefore, the focus of this field trial lies on the short-term N-supply to the crop by the fertilizer.