Vegetable crop residues as feedstock for composting and silage: collection efficiency and product quality

The crop residues of vegetables are important for nutrient and organic matter cycling. However, these residues often may lead to nitrogen leaching risks. This study investigates the feasibility of removing crop residues, followed by composting or ensiling as a means to reduce N leaching losses. Ensilage conserves the nutrients for reuse on the field after the winter or for other applications (e.g., anaerobic digestion), while composting results in stabilisation of the organic matter before application in the field. Crop residues of cabbage were mechanically harvested with common available equipment at two different moments: the end of summer and the end of fall. The residue collection efficiency was low as the collected material had high soil particle load. For composting, residues of white cabbage or leek were mixed with wood chips and bark, straw and corn stover for a good compost composition. For silage, crop residues of white cabbage, celery, cauliflower or leek were mixed in a 50/50 volume ratio with chopped corn stover. Feedstock materials, composts and silage were analysed for (bio)chemical characterisation. Silage quality was optimal for the mixtures with leek and celery, and less optimal for the other mixtures. This was related to higher NH4+-N concentrations and lower compressibility of the mixtures with cauliflower and white cabbage. Composting was suboptimal due to the high soil particle load of the crop residues and the corn stover. New silage and compost experiments are run in 2014.