Agriculture Reference
In-Depth Information
implicated in exacerbating numerous diseases. Composted biosolids applied to nu-
trient-deficient soils, improved turfgrass resistance against leaf rust severity caused
by Puccinia sp. by enhanced nitrogen nutrition (Loschinkohl and Boehm 2001 ).
Minor specific elements can also play a role in increasing plant disease resis-
tance. Enhanced foliar content of Mo, Ca and Si in compost amended cucumber
plants was positively related to increased suppressivity against Botrytis cinerea
(Segarra et al. 2007 ). Instead, Al has been indicated to be functional for suppressive
media against damping-off of ornamental bedding plants caused by Phytophthora
parasitica (Benson 1995 ). Hydrophobic humic molecules in compost are believed
to directly or indirectly improve its disease control capability (Mathur 1991 ). Pas-
cual et al. ( 2002 ) verified this property by separately assaying the various fractions
of municipal compost in a suppressive assay with Pythium ultimum on pea seedling.
The mechanisms by which composts and their humic fractions inhibit plant patho-
gens are not fully understood, although recent studies showed a significant relation-
ship between the chemical and functional properties of humic substances and their
capacity to suppress soil pathogenic fungi (Loffredo et al. 2007 , 2008 ).
8.3.3
Physical Aspects of Composts Suppressivity
The compost is able to modify the physical environment in which disease devel-
ops by affecting moisture, free water containment, pH, electrical conductivity, tem-
perature, water-holding capacity and bulk density (Chen et al. 1988 ; Hoitink et al.
2001 ). Of course, all the changes determining conditions that are unfavorable to
pathogen growth and pathogenesis activation, lead to suppressivity.
8.4
Ecological Aspects Related to Compost Suppressivity
As seen, the microbial community in compost was considered to be the most
significant factor of plant pathogens inhibition in function of its suppressive-like
structure. Ecological relationships among microbes that achieve over time within
the compost nutritional niches in the time, move a sort of dynamic evolution process
that involve both biological and non-living factors (Fig. 8.3 ). Changes in microbial
communities induced by the carbon food competition have relevant implications on
functionalities, including those linked to suppressivity (Pane et al. 2011 ). Quality
and bioavailability of organic matter has been linked to compost ability to provide
biotic suppressivity (Veeken et al. 2005 ; Termorshuizen et al. 2007 ). Boehm et al.
( 1997 ) demonstrated the crucial role played by NMR-assessed carbohydrates to
sustain peat microflora antagonism against Pythium ultimum on pea. While, shifts
in microbial communities favored by phenolic and methoxyl C fractions, were con-
sidered to be decisive for the reduction of Rhizoctonia and Sclerotinia damping-off
of Lepidium sativum (Pane et al. 2013 ). Similarly, (CastaƱo et al. 2011 ) evidenced
the relevance of hydrophylic carbon moieties in compost-based bio-control of
Search WWH ::




Custom Search