Vegetable crop residues take a particular position relative to arable crops due to often large amounts of biomass with a N content up to 200 kg N ha−1 left behind on the field. An important amount of vegetable crops are harvested during late autumn and despite decreasing soil temperatures during autumn, high rates of N mineralization and nitrification still occur. Vegetable crop residues may lead to considerable N losses through leaching during winter and pose a threat to meeting water quality objectives. However, at the same time vegetable crop residues are a vital link in closing the nutrient and organic matter cycle of soils. Appropriate and sustainable management is needed to harness the full potential of vegetable crop residues. Two fundamentally different crop residue management strategies to reduce N losses during winter in intensive vegetable rotations are reviewed, namely (i) on-field management options and modifications to crop rotations and (ii) removal of crop residues, followed by a useful and profitable application.

No abstract

The need to meet rapidly increasing demands for synthetic nitrogen (N) while reducing dependence on fossil fuels has been driving widespread attention to the recuperation and reuse of nutrients present in digestate and animal manure. The N release and mineralization potential of animal manure (AM), digestate (DIG), liquid fraction of digestate (LFDIG) and mineral concentrate (MC) were assessed in comparison with N availability from calcium ammonium nitrate (CAN) as a reference. The release was highly dependent on the product NH4+-N/N-total ratio, while mineralization occurred only for products containing more than 5% of organic N. The magnitude of the released N, on average after 120days of an incubation experiment, was in the order: CAN>MC>LFDIG>DIGAM. These results indicate that only the N release from MC exhibited patterns similar to CAN, suggesting that this product will provide plant available N in a similar fashion as synthetic fertilizers. The N release from LFDIG was higher than AM, but did not closely follow the pattern of CAN. The N availability in LFDIG may be increased using substrates richer in N, such as animal manure or waste food and not only plant residues

No abstract

No abstract