While organic matter decomposes, nutrients are released and fulvic acids are formed. Fulvic acids are resistant to decomposition and polymerize to form humic substances in soils. Fulvic and some humic acids remain dissolved in water in soil early during the decomposition process. These acids chelate trace elements, such as iron, zinc, manganese, copper, etc., and improve the availability of these elements in soils. Highly stabilized sources of organic matter, such as that in muck soils or peat, as well as humic substances in mineralized farm soils, do not provide these same beneficial effects.
Pathogens typically cause heavy losses in such soils unless pesticides are used.
Composts prepared from yard wastes, manures, and sewage sludges tend to release significant quantities of nutrients for plant growth. They also may be high in salt content, which can present problems. These products need to be applied based on the fertility requirement for the crop. However, since the nutrients are released over several years, large amounts can be applied relative to the same amounts of nutrients in manufactured fertilizers. One half bushel of these products per tree gives positive effects on tree crops for the reasons given previously.