Agriculture Reference
In-Depth Information
are being used for turf grass applications on European golf courses or other sports turf at
present, although preliminary research in the UK has indicated positive benefi ts (Lawson &
Brundage, 2006).
5.7.4
Factors affecting disease suppression
Several direct and indirect factors affect the extent to which composts confer disease
suppressiveness in fi eld soils and growing media. It is acknowledged that the addition
of organic amendments (including composts) to fi eld soils often leads to improved soil
structure, water penetration and drainage, enhanced soil health and greater complexity
of microorganisms and soil food webs (van Bruggen, 1995). Most organic amendments
commonly applied on farms and holdings are acknowledged to benefi t soil health,
particularly if applied regularly over an extended period of time (Doran
et al
., 1996;
Albiach
et al
., 2000; van Bruggen & Termorshuizen, 2003). The health and quality of
crops grown in soils of high health status is likely to be better than that of those grown in
poor soil conditions, hence the addition of organic amendments may indirectly improve
crop health. The application of organic amendments often results in increased populations
of both soil microfl ora and soil fauna. However, it is thought that the complexity of the
soil ecosystem at the lower trophic levels is most important in relation to the suppression
of plant disease, since fungal and bacterial plant pathogens are affected most by micro-
organisms at these lower trophic levels (van Bruggen & Termorshuizen, 2003).
The following factors have been identifi ed as determinants of success in biological
control of plant pathogens with composts:
•
level of compost maturity and the degree of decomposition of the organic matter;
feedstock type(s), and the composting system;
•
chemical and physical attributes of the compost, which affect the activity of benefi cial
•
and pathogenic organisms within it and the susceptibility of the host plant to disease
(these are largely determined by the feedstock type(s), composting system, level of
compost maturity and degree of decomposition of the organic matter);
biological attributes of the compost, which play an important role in determining its
•
suppressiveness (in particular, the presence of plant pathogens and biological control
agents). Again, these are largely determined by the feedstock type(s), composting sys-
tem, level of compost maturity and degree of decomposition of the organic matter);
the presence of biological control agents (which can affect disease suppressiveness)
•
added to the compost after composting.
The above factors are discussed in more detail in the following pages.
5.7.4.1
Feedstock type and composting system
Composts made from a wide variety of feedstocks have been used with success to control
pathogens. In most cases, the feedstocks have been chosen due to their low cost and/
or ease of procurement in the geographical area in question. However several workers
have shown that composts made using similar methods but from different feedstocks may
perform differently. For example, de Brito Alvarez
et al.
(1995) found that three out of
