Fertilisation of potted geranium with a municipal solid waste compost

A greenhouse pot study was conducted to evaluate the use of a municipal solid waste compost (MSWC) as a fertilizer for potted geranium (Pelargonium x hortorum Bailey) cv. Meridonna. MSWC was mixed with a peat-based growing-media at rates of 0%, 10%, 20%, 30%, 40% and 50% by volume. Plants grew in those mixes for 90 days, with no additional fertilization. MSWC increased the electrical conductivity (saturated extract) of the growth-media linearly from 1.4 mS cm−1 at 0% to 12 mS cm−1 at 50% MSWC. 10% and 20% MSWC promoted the highest plant growth, although these plants showed low leaf concentrations of nitrogen and phosphorus. The lowest yield was obtained at 0% MSWC caused by a low level of available nutrients in the growth-media. Application rates of MSWC >20% reduced plant growth as a consequence of the high level of salts, and rates 40% resulted in high levels of copper. The results of this experiment showed that potassium, magnesium, calcium and micronutrients requirements of geranium were provided with 20% MSWC, indicating that this crop could be grown in peat-based substrates with 15–20% of MSWC, as long as adequate amounts of nitrogen and phosphorus were being provided.