Use of Herbage Compost as Horticultural Substrate and Source of Plant Nutrients

Abstract

ABSTRACTThe potential of herbage composts as horticultural substrate and source of nutrients was investigated. The effect of botanical composition of the herbage, as well as the effect of different kinds and amounts of carbon sources, on nitrogen losses during composting and growth properties of the compost were studied. Growth tests with different plant species as well as chemical analyses of total- and easily-soluble plant nutrients were used to evaluate compost quality. Seven herbage composts were studied and used in growth tests with seven different test plants. The results were evaluated by conventional and multivariate statistical methods.Accumulated nitrogen losses tended to vary with carbon source added, and were 2–25% of the initial N content over a 130-day composting period. Plant growth and seed germination were largely explained by the electrical conductivity of the compost mixes. Potassium concentrations were very high in the composts. The results showed the possibility of using herbage composts as part of a substrate for container-grown vegetables and flowers. All of the composts which were tested required mixing with nutrient-poor material in order to become a suitable substrate, mainly to avoid excessive conductivity. In a substrate based on sphagnum peat, 10–100% of the peat might be substituted with herbage compost, depending on the amount of carbon source added during composting. A considerable amount of the plant nutrients needed in the substrate for the initial six weeks of plant growth was found to be supplied by the herbage compost.