Agriculture Reference
In-Depth Information
wrongly labelled as composts). A limited number of studies have shown that fresh or
stacked manures have enhanced suppression of soil-borne diseases. For example,
damping-off of radish and lesion development caused by
Rhizoctonia solani
was reduced
in plot experiments in Iowa where manure was added in comparison with non-amended
controls (Voland & Epstein, 1994). Similarly, fresh chicken manure has been shown to
reduce survival of the pathogen
Phytophthora cinnamomi
and the incidence of symptoms
on
Lupinus albus
seedlings (Aryantha
et al
., 2000). The impact of manures on disease
incidence and severity is however, much less predictable than that of composts and several
workers have shown that the application of manures to soils can increase the incidence and
severity of pests and diseases (Roy & Newhook, 1970; Aryantha
et al
., 2000). Available
evidence suggests that composts are likely to give more predictable, consistent control
of plant diseases and that research efforts would be better directed towards developing
composts as aids to crop protection in organic systems, rather than manures.
5.7.3
Turf
Considerable work has been done, mainly in the United States, to determine the effects of
composts used on turf grass diseases. Most of this work relates to golf courses, with the
result that compost is now widely used on US golf courses to control a range of fungal
diseases.
When used as top dressings, composts have been consistently been shown to suppress
disease in comparison with untreated turf or turf dressed with either sand or topsoil
(Nelson & Boehm, 2002). Diseases suppressed or controlled include those caused by foliar
pathogens [red thread (
Laetisaria fuciformis
), brown patch patch (
Rhizoctonia solani
),
dollar spot (
Sclerotinia homeocarpa
), typhula blight (
Typhula incarnata
) and pythium
blight (
Pythium aphanidermatum
)] and root pathogens [summer patch (
Magnaporthe
poae
), pythium root rot (
Pythium graminicola
) and necrotic ringspot (
Leptosphaeria
korrae
)]. Levels of disease suppression varied between 0 and 94%, depending on the
disease, the amount of compost used, the type of compost, the experimental year and the
researchers concerned. Feedstocks of composts which have successfully suppressed turf
grass diseases include animal manures, industrial and municipal sludges, greenwaste (or
yard trimmings), grass clippings and food residuals. Monthly applications of topdressing
composed of as little as 20% compost by volume and applied at rates of 10 lbs compost/
1000 ft
2
(488 kg compost ha
1
) have been suffi cient to suppress disease. In the short
term, disease control has often been shown to be less effective with composts than with
fungicides. However, work has shown that in the longer term, turf quality and the level
of disease control obtained using composts can be better than where fungicides are used.
Composts have also been tested on United States golf courses as 'winter covers'
(applied at approximately 1.25 cm depth during the winter months only to protect the
grass) and root zone amendments (compost is brushed in to the hollow cores in the turf
root zone made using hollow tine aerators). Composts used in both applications have
been shown to suppress disease. For example, seedling establishment was enhanced and
Pythium root rot was suppressed where the turf root zone was treated with compost based
on municipal biosolids or brewery sludge (Nelson & Boehm, 2002). Preliminary studies
have shown that the application of compost as a winter cover can protect turf grasses from
snow mould damage in winter and early spring. There is little evidence that composts
