Municipal Compost as a Nutrient Source for Organic Crop Production in New Zealand
Authors: Abie Horrocks, Denis Curtin, Craig Tregurtha and Esther Meenken
About 1% of New Zealand farmland is managed organically. Nitrogen is the nutrient most likely to limit organic crop production. A potential solution is incorporation of compost to supply N. About 726,000 t of municipal garden and kitchen wastes are sent to landfills annually. Composting offers a means of reducing the impact of landfill wastes on the wider environment. Organically certified compost (N content typically 2% to 2.5%) is available from some municipal composting plants. To be effectively used on organic farms, the rate of N release (mineralization) must be known. Laboratory incubations were conducted to quantify mineralization of compost N under controlled (temperature and moisture) conditions. Nitrogen availability and crop yields from a one-off application of compost (25–100 t·ha?1) were also assessed in two field trials (using cereal and forage crops). The results suggested that a relatively small part (13%–23%) of compost N was used by the crops in 3–4 years. Much of this was mineral N present at the time of application. Mineralization rates in the laboratory and field studies were much lower than expected from published work or compost C:N ratio (considered an important indicator of N mineralization potential of composts).
Illustration Photo: compost bin (Public Domain from Pixabay.com) https://adalidda.net/posts/9XrM9gLfBhWp25QMZ/municipal-compost-as-a-nutrient-source-for-organic-crop