Agriculture Reference
In-Depth Information
(e.g., rotations with legumes and disease- and weed-suppressive cover crops), and
avoiding physical (mechanical) interventions that might compact, alter, or destroy the
biologically created porous structural arrangements of soil components (FAO 2008).
A key factor for sustainability in any production system, in contrast to sustainable
intensification, was described by Uphoff et al. (2006) as follows:
Of particular importance for sustainable agriculture is the enhancement of soil water-
holding capacity and drainage. This is very dependent on the kinds of biological activ-
ity that lead to better particle aggregation, creating soil that can be both better aerated
and infused with water at the same time. …Improving soil characteristics through
biological activity and management will store water, the most essential source for agri-
culture, in soil horizons and root zones where it is most needed…
Similarly, in FAO (2008), it was described as follows:
Sustainability of land's capacities to continue yielding both plant products and water
year after year depends primarily on maintaining the soil in fit condition for active life
processes of the whole soil/plant system. This relates to the ongoing generation and
re-generation of the porous soil architecture—the soil's 'self-recuperation capacity'—
with respect to the repair of damaged soil and to its physical resilience in the face of
adverse shocks of weather and/or of poor management.
It is now recognized more widely that a productive agricultural soil, together with
its inhabiting plants and other biota, is a living biological system (Tikhonovich and
Provorov 2011; Doran and Zeiss 2000; Doran 2002) that is made up of a complex web
of interactions between a large diversity of microorganism and mesofauna and between
microorganisms and plant roots as well as aboveground parts. Relatively little is known
about this complex agrobiodiversity or soil biota and its ecosystem functions as its role in
crop productivity has been generally ignored, even during the recent decades.
For example, four main aggregate ecosystem functions are performed by the below-
ground soil biota (Swift et al. 2008): (1) decomposition of organic matter brought about
by the enzymatic activity of bacteria and fungi, and facilitated by soil animals such as
mites, millipedes, earthworms, and termites; (2) nutrient cycling, which is closely asso-
ciated with biological nitrogen fixation, uptake of various nutrients from lower soil
horizons, organic matter turnover, and organic decomposition, with transformations
mediated through microorganisms; (3) bioturbation through the activities of plant roots,
earthworms, termites, ants, and some other soil mesofauna and macrofauna that form
channels, pores, aggregates, and mounds, and physically moving particles from one hori-
zon to another; and (4) disease and pest control through, for example, the regulations of
activities of pathogens by the microbivore and micropredator portions of the soil biota
that feed on microbial and animal pests, respectively.
The above-described soil biological processes and ecosystem functions cannot be
performed adequately in soils that are mechanically disturbed by tillage and whose
structure and porosity are repeatedly impaired as a result. Soil biological health is
further hindered by the inadequate amount of organic substrate being supplied to
feed and maintain soil microorganisms and their functions at rates equal to, or faster
than, its rate of oxidation following tillage.
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