Intercropping beans with maize also decreases the incidence and severity of bacterial blight and rust (Fininsa 1996).
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).
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.