Chemistry Reference
In-Depth Information
substantial soil erosion by either water, tillage or wind so that the current
mobilisation of soil globally is 35 (ยก10) Pg yr
21
or about 5 t yr
21
for every
person on the planet.
76
In addition, the clearance of forests for agriculture has
led to decreased biodiversity and substantial inputs of greenhouse gases to the
atmosphere. This has led many to challenge the technologies that have resulted
in today's intensified agriculture and to call for the development of sustainable
production practices that will ensure that the multiple functions of land, and
the many ecosystem goods and services provided by land, are conserved and
sustained for future generations.
77-80
Although there is general agreement that agricultural sustainability includes
elements of profitable production, environmental stewardship and social
responsibility, there is much less agreement as to how sustainability is to be
achieved in practice beyond the need to integrate biological and ecological
insights into the production process. A review of the literature suggested that
sustainability encompassed four key principles that
78
''(i) integrate biological
and ecological processes such as nutrient cycling, nitrogen fixation, soil
regeneration, allelopathy, competition, predation and parasitism into food
production processes; (ii) minimise the use of those non-renewable inputs that
cause harm to the environment or to the health of farmers and consumers; (iii)
make productive use of the knowledge and skills of farmers, thus improving
their self-reliance and substituting human capital for costly external inputs;
and (iv) make productive use of people's collective capacities to work together
to solve common agricultural and natural resource problems, such as for pest,
watershed, irrigation, forest and credit management''. Such principles go well
beyond the need for continued technological innovations, such as new
germplasm underpinning increases in yield, and embrace the need to develop
important capital assets for agricultural systems, including natural, social,
human, physical and financial capital. A corollary of this analysis is that many
disciplines and ways of thinking will be required to develop sustainable systems
and that there is unlikely to be a single solution appropriate to all soils and
production systems.
Soil is a component of the natural capital used by humans for food
production, and the functions provided by soils are major contributors to
almost all of the provisioning, regulating and cultural services provided by
ecosystems.
77
But using soils for agriculture almost invariably leads to changes
in soil properties such as nutrient status, pH, organic matter content and some
physical properties as interventions are made to influence soil fertility. These
changes, while beneficial to crop production, are often detrimental to other
ecosystem services so that there is tension between the different functions
undertaken by soils.
80
There is little doubt that, for most soils, sustainable
production is inextricably linked to the maintenance of soil organic matter
contents through appropriate additions to offset the losses caused by
cultivation and nutrient depletion.
68,81
Soil organic matter influences many
key processes including release of greenhouse gases (GHGs), nutrient cycling,
microbial and faunal diversity, and many soil physical properties.
80
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