Agriculture Reference
In-Depth Information
utilising microorganisms during post-harvest processing, is the potential for late-
season applications of compost tea to alter microbial population (e.g., yeasts) on the
fruit surface. These changes may not be an issue if potentially deleterious microor-
ganisms do not survive post-harvest processes like fermentation or heat treatment.
Regional variation in produce quality is a critical feature of perceived prod-
uct identity and consumer appreciation. Knowledge of the microbial diversity of
crop plant surfaces over time and space (Peiffer et al.
2013
) are likely to provide
important baseline information for understanding the consequence of adding micro-
organisms to that environment through application of compost tea or other human-
mediated actions. There is evidence to suggest that microbial populations associated
with wine grape surfaces are non-randomly associated with regional, varietal and
climatic factors (Bokulich et al.
2013
). It is not known if regional differences in
microbial communities modulate wine sensory qualities; however, further studies
might improve understanding of how these factors interact with interventions such
as biological control to influence produce quality.
Even though many practitioners are committed to the philosophy of organic agri-
culture, there are still a number of questions about whether or not some approaches
to disease management are environmentally and/or economically sustainable. Ev-
ery time a spray is applied using tractor-driven machinery it uses (fossil) fuel and
labour, with multiple passes of a tractor potentially contributing to soil compaction.
The latter can be mitigated to some extent using controlled-traffic farming (Gasso
et al.
2013
). It could be argued that in some situations a single application of a well-
timed and highly effective synthetic fungicide might be a more sustainable practice
than multiple applications of a less effective organic crop protectant. Conversely, a
single application of an effective organic crop protectant could suffice if the deci-
sion to apply the material is informed by a useful system for disease-risk assessment
(Gent et al.
2013
) and, if necessary, integrated with suitable cultural controls. Com-
post teas might be particularly useful in fields where the local pathogen population
has developed resistance to commonly used fungicides. Breeding, selecting and/or
mixing crop cultivars with durable disease resistance is perhaps the most sustain-
able disease management practice of all.
9.9
Future Research
Despite a gradual increase in the number of refereed, scientific reports about com-
post teas, additional replicated trials over many sites and seasons are needed to sup-
port, or otherwise, the many anecdotal claims made by practitioners about disease
suppression. Microbial diversity in compost tea and on plant surfaces before and
after application to crops can be studied further by analyses of community DNA;
for example, actinobacteria are known to be present in early secondary mesophilic
compost (Herrmann and Shann
1997
) and their diversity could be studied by appli-
cation of appropriate analyses of community DNA (Conn and Franco
2004
; Osborn
et al.
2000
).
