Intercropping for enhancement and provisioning of ecosystem services in smallholder, rural farming systems in KwaZulu-Natal Province, South Africa: a review

ABSTRACT Monocropping of maize (Zea mays L.) and communal grazing of livestock (cattle) are the major farming systems for smallholder farmers in the Upper Thukela region of KwaZulu-Natal, South Africa. However, these farming systems are unable to contribute meaningfully to sustainable food security and viable livelihoods. This is because of continuous declines in crop productivity and soil fertility under monocropping systems and shortages of adequate and good quality forage under communal grazing systems. Although the benefits of intercropping have been well documented, there has been low uptake by small-scale farmers in the temperate, frost-prone communal areas of KwaZulu-Natal. This may be attributed to a lack of research applicable to this region as well as to a lack of understanding of how these systems can address the social and technological challenges faced by these farmers. The latest advances in agroecological farming systems are reviewed here to enable small-scale farmers to better assess the benefits relative to ecosystem services that are compatible with their needs. One such service is the provision of food through nutrient cycling. Available nitrogen (N) and phosphorus (P) are the most limiting nutrients in the soils, which are acidic in nature, of this high-rainfall area of KwaZulu-Natal, South Africa. This results in poor crop productivity and quality, particularly in smallholder, rural farming systems. High costs of chemical fertilizers, which most smallholder farmers cannot afford, and cropping systems involving monoculture, exacerbate the macro-nutrient deficiency, which leads to low crop yields and quality, feed scarcity, plant pests and diseases, resulting in reduced viable livelihoods and household food insecurity. One option to alleviate the situation is by the use of mixed cropping systems in the form of intercropping, the practice of growing two or more crop species at the same time and in the same place. This review explores, elucidates and summarizes the capability of intercropping to augment agroecosystem services essential for sustainability of smallholder, rural farming systems. The review highlights ways in which intercropping can address the socio-economic needs and aspirations of communities and conserve resources for the benefit of the local environment. Niche differentiation (facilitation and complementarity of resources); soil fertility; crop genetic diversity; management of pests, diseases and weeds; crop production; environmental sustainability and economic viability are discussed, as are the mechanisms underlying provisioning of ecosystem services. We have highlighted that intercropping farming systems considerably improve soil fertility, resource-use efficiency, carbon sequestration, phosphorus uptake and availability, water conservation in soils, crop and fodder productivity and quality and control pests and diseases compared with monoculture farming systems. The other major latest development in mixed-cropping systems is that crop genetic diversity resulting from intercropping contributes in various ways towards reducing incidences of pests and diseases. Technologies and mechanisms that have potential to enhance key ecosystem services for promoting sustainable food systems of rural farmers in KwaZulu-Natal are highlighted.