Making soil biodiversity matter for agriculture - Microbial Ecology in Sustainable Agroecosystems - page 271

to threats, depending on the type of ecosystems, the spatial and temporal scale, and the
organisms present. This reflects the fact that the climatic and edaphic factors of each soil
type define the organisms in it and is valuable knowledge for planning future land man-
agement for food and fiber.
10.4 Management of soil biodiversity for disease
regulation and crop yield
An ecosystem service provided by soil biodiversity is the control or suppression of organ-
isms that cause damage to or kill a plant, animal, or human. There have been substantial
gains in our understanding of belowground organisms as biocontrol agents of root para-
sites and herbivores because of their effect on other ecosystem services (plant production
and crop yield) (Brown and Gange, 1989; Kerry, 1998; Blackshaw and Kerry, 2008; Seastedt
and Murray, 2008; Johnson, 2010). This gain has been due to the search for alternative pes-
ticides, the growing awareness of harm to humans and the environment resulting from
pesticide use, and curiosity-driven ecological research. The history of research to control
plant parasitic nematodes in agriculture has included, but is not limited to, use of para-
sitoids, predaceous microbes, and invertebrates, planting cover crops such as marigold
( Tagetes spp.), which produces allelopathic compounds such as alpha-terthienyl (Riga et al.,
2005), resistant plants, and designed landscapes for enhanced growth of biological control
organisms (see review by van der Putten et al., 2006).
Disturbance to soils with increasing agricultural intensification can reduce species
diversity and affect the biological regulation of parasites and predators, which in turn
could affect the delivery of ecosystem services ( Figure 10.1 ; Tian et al., 1992; Bloemers et
al., 1997; Eggleton et al., 2002; Heemsbergen et al., 2004; Hol et al., 2010). However, effects
of soil disturbances on species diversity can vary considerably, depending on the biology
of the organism (Wall et al., 2010). Knowing the plant host and the biology, the spatial and
temporal patterns, and the food preferences of the soil pathogen/pest, as well as the types
of associated organisms that constrain growth of the pathogen, pest, or herbivore, is key
By agricultural inputs
By soil organisms
Agricultural Intensification
Figure 10.1 Increasing intensification of agriculture, including increased chemical (e.g., pesticides,
fertilizers) inputs, adversely affects the benefits provided by soil microbes and invertebrates such as
those that contribute to the biocontrol of root pathogens and regulate soil fertility.