Perspective

Compost Science & Utilization, (2009), Vol. 17, No. 2, 71

Compost(’s)ability

Fred Michel, Jr.

Composting has long been known as a process with two important abilities: to recycle organic materials and to generate amendments that improve soil properties. As the price of synthetic fertility sources increases with the depletion of fossil energy, and the long term environmental impacts of their use, especially as agriculture expands to meet world food needs, become known, it is clear that more emphasis will be placed on the use of composts as sources of crop nutrients and soil improvement.
Many studies have examined the ability of composts to enhance fertility, soil water holding capacity, cation exchange capacity and porosity, and to suppress plant diseases. However it has also been shown that care must be taken in the selection of feedstocks, the production, and the use of composts to achieve these benefits. In this issue of Compost Science & Utilization (CSU), five articles assess the use of compost as a soil fertility source in a variety of agricultural applications. Nitrogen release dynamics have always been an important question regarding the use of compost. In their article, Passoni and Borin point out the importance of understanding the availability of nitrogen before using composts for agricultural production. They show that composts made from different feedstocks have varying abilities to supply nitrogen for plant growth.
Paul Hepperly and colleagues in Pennsylvania present the results of a long-term study showing the benefits of composts used as a fertility source as compared to manure and synthetic fertilizers. In a corn, wheat, vegetable rotation they find that over the long term, compost is superior to manure and fertilizer in providing soil fertility and reducing nitrate pollution. Pilar Mazuela and Miguel Urrestarazu use a leaching treatment to remove excessive salts from composted greenhouse plant residues and show that the compost can then be effectively recycled as a component of soilless growth media.
Following up on a 2007 CSU article about the effects of turning and vessel type on backyard compost production, Paul Alexander assesses the suitability of backyard composts as potting media for tomatoes and lettuce. Finally, a study by a group from Nova Scotia, where organics are banned from landfilling and largely diverted to composting, examines the use of this type of compost, and teas made from it, as fertility sources for the production of strawberries. Together the studies define many positive effects, as well as some potential drawbacks, associated with using composts to grow crops. — Fred Michel, Jr.

Copyright 2007, The JG Press, Inc.