Agriculture Reference
In-Depth Information
5.10
Conclusions and future work
There is increasing pressure on farmers to reduce pesticide use, whilst maintaining crop
quality and yields. At the same time, production of composts from organic wastes is ris-
ing as most developed countries are attempting to reduce volumes of waste being sent to
landfi ll. There is growing evidence that the use of composts and compost extracts/teas
can help suppress plant diseases as part of integrated disease control strategies through
improvements in soil health and through direct control of diseases.
In a few documented cases, control of specifi c diseases using composts or compost
extracts/teas in conventional agricultural or horticultural systems has been equal to or
better than that achieved with synthetic pesticides. However, for many pests and diseases
the level of control, which has been demonstrated in glasshouse and fi eld trials, is lower
than that normally considered acceptable for conventional growers. Commercial and
domestic produce buyers may fi nd it diffi cult to accept that the quality and yield of
conventional crops treated in this way are often lower. For organic growers, who have no
access to synthetic fungicides, composts and compost extracts/teas may provide particu-
larly useful additions to the range of partial disease control solutions to which they have
access.
Considerable further work is required to develop protocols that can be used to ensure
predictable and reliable disease suppression or control through application of composts
and compost extracts/teas on cropping systems and turf in different soil types.
The majority of research that has yielded commercially important results to date has
concerned lignin-rich composts, based for example on tree bark. Given that most of the
composts now being produced on a large scale in Europe and North America are based on
other feedstocks, (mainly organic wastes including green [or yard] and vegetable wastes),
further research is required to determine how to optimize their production and use to
favour suppression of plant disease in modern crop production systems.
In particular, work is required to determine consistently effective methods to predict
disease suppressiveness in composts. Some of the newer techniques based on organic
matter characterization or assessment of microbial species diversity or functional diver-
sity may prove helpful in this case.
Several workers have acknowledged that the use of composts of poor or inappropriate
quality may have led to low levels of disease suppression. For this reason, the relative
importance of several biological, chemical and physical parameters of compost require
further study in order to facilitate production of reliably suppressive composts. Several
workers have demonstrated that the amendment of composts with specifi c biological con-
trol agents can result in enhanced disease suppression and some composts have been
shown to be excellent carriers of such biological control agents. However, further work is
required to ensure that the composts into which these biological control agents are intro-
duced have optimal chemical, physical and biological properties to allow rapid coloniza-
tion by the introduced organisms.
Many of the recent reports of improved plant growth or successful disease control using
compost teas are based on anecdotal information or commercially sensitive data held by
private companies. There is a need for independent research to demonstrate the effects
of compost teas and to elucidate the mechanisms behind reports of disease suppression
or improved plant growth. Evidence from recent work suggests that the use of particular
