Agriculture Reference
In-Depth Information
Chapter 5
The use of composts and compost
extracts in plant disease control
Audrey Litterick 1 and Martin Wood 2
1 SAC Environmental, Craibstone Estate, Aberdeen, UK
2 Earthcare Environmental Ltd., Reading, UK
5.1
Most developed countries throughout the world are now attempting to reduce the amount
of biodegradable waste that is sent to landfi ll. Composting is a viable option for treating
such wastes, not least because the fi nished product is a bulky fertilizer with useful
applications in agriculture, horticulture and landscaping. There is a considerable body
of evidence to show that composts and liquid preparations made from them can suppress
or control plant diseases. However, the effect of these composts and compost extracts (or
compost teas) on the soil and leaf microfl ora and on plant diseases varies greatly, depend-
ing on the nature of the compost (or liquid preparation), its preparation method and on the
context in which the material is used.
This chapter aims to defi ne composts, compost extracts and teas, to outline prepara-
tion methods and to summarize the fi ndings of recent work which demonstrates their
effects on plant disease. The mechanisms which are responsible for disease suppression
and control will then be discussed, the problems associated with using composts and
liquid preparations will be reviewed and the future potential for using composts in crop
production systems will be considered.
Introduction
5.2
Defi nitions of composts, composting, compost
extracts and compost teas
Composts and the composting process
5.2.1
Compost can be defi ned as solid particulate organic material that is the result of compost-
ing, that has been sanitized and stabilized and that confers benefi cial effects when added
to soil and/or used in conjunction with plants. Composting can be defi ned as a process
of controlled biological decomposition of biodegradable materials under managed con-
ditions that are predominantly aerobic and that allow the development of thermophilic
temperatures as a result of biologically produced heat, in order to achieve compost that
is sanitary and stable. Compost production is briefl y described later in this paper, but the
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