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resulted in an 8 per cent increase in the yield of wheat. Stanger
and Lauer (2008) made similar findings in a study spanning
35 years. Together with conservation tillage, crop rotation has
been shown to significantly increase structural stability of soil and
the concentration of organic carbon in a 0–8 centimetre depth of
soil. This has the potential to maintain crop productivity, protect
the soil and improve soil quality (Carter and Sanderson 2001).
According to Lithourgidis
et al.
(2011), inter-cropping results in
greater yields due to the use of a mixture of crops with different
but complementing rooting ability, canopy structure, height
and nutrient requirements. For example, inter-cropping maize
with cowpea increases light interception in the crops, reduces
water evaporation and improves conservation of soil moisture
compared with a maize mono-crop (Ghanbari
et al.
2010). The
soil is better conserved through greater ground cover than
in mono-cropping, while the incidence of pests and diseases
is also reduced. Inter-cropping enhances the abundance of
predators and parasites, preventing the build-up of pests
and reducing the use of chemical pesticides. For example,
black aphid (Aphis fabae) infestations of beans are lowered
when beans are intercropped with taller maize plants, which
interfere with aphid colonization (Ogenga-Latigo
et al.
1993).
Intercropping beans with maize also decreases the incidence
and severity of bacterial blight and rust (Fininsa 1996).
There is growing interest in integrated farming due to its
potential for profitability and stability of farm income, long-
term sustainability and greater food yields as well as because of
concerns about natural resource degradation (Russelle
et al.
2006).
Integrated crop-livestock systems foster diverse cropping
systems, including seasonal and perennial legume forages
and cereals, which bring multiple environmental benefits. For
example, integrated systems may use animal manure, which
enhances soil fertility, while the perennial crops are important
for carbon sequestration (Russelle
et al.
2006).
The Millennium Ecosystem Assessment (MA 2005) strongly
suggested that in order to meet the need to increase global food
output there should be more emphasis on the development
of environmentally and ecologically sound methods for the
intensification of food production. Systems such as crop
rotation, mixed cropping and integrated farming provide greater
sustainability than approaches that solely use chemicals and
other non-ecosystem-based practices.