Horticultural growing medium components must be selected with regard to their influence on properties such as cost, availability, ease of mixing, appearance, pH, nutrient levels, soluble salt levels, exchange capacity, aeration, particle size distribution, bulk density, water-holding capacity, and consistency. Over the past several decades, various types of compost products made from urban waste materials have been evaluated as components in horticultural growing mixes. The highest-quality compost products tested have frequently compared favorably with peat as one of the organic components in growing mixes. The lowest-quality compost materials tested have retarded plant growth and, in extreme cases, contributed to plant mortality. Occasionally, compost products that performed well in research trials did not prove to be satisfactory when used in commercial nursery crop production because of the lack of repeatable consistency between batches produced in large-scale municipal composting operations. One of the major reasons for the lack of consistency in compost quality is the highly variable nature of organic feedstocks accepted by many large-scale composting operations. The highest-quality composts tend to be produced in composting operations in which facility management decisions are made with consideration on their impact on the economic, physical, and chemical parameters of the end product.
If the inline PDF is not rendering correctly, you can download the PDF file here.