African Journal of Range and Forage Science 2015, 32(2): iii–iv http://dx.doi.org/10.2989/10220119.2015.1060693 Copyright © NISC (Pty) Ltd It is estimated that the world population will reach nine billion people by 2050, which creates a number of challenges for agriculture (Godfray et al. 2010). More food needs to be produced from smaller areas, and this should be done in ways that promote sustainability, both socially and environmentally. Agriculturalists face the inevitable problem of attrition of the areas available to produce agricultural products due to degradation, increased population pressures and urbanisation. These problems also threaten cultivated pastures or improved rangelands in southern Africa, which contribute significantly to food security in this region. A total of 151 million ha of southern Africa’s agricultural area is covered by permanent meadows and pastures (FAO 2014). Although the majority of this area is natural grasslands and not managed to arrest successional processes, certain areas with lower agricultural potential have been intensified to improve pasture production for grazing animals, or to harvest forage for utilisation by animals off-site or at a later stage. Research and development of technologies that either increase, sustain or avoid losses of productivity is imperative to increase the efficiency of production from pastures and, at the same time, ensure environmental sustainability. However, research on cultivated pastures is scarce or outdated despite the need to improve production from these areas. The aim of this special issue of the African Journal of Range and Forage Science is to introduce past and current research on pastures in southern Africa, to highlight the research priorities in pasture science and to provide an agenda for future research in this discipline. The lead review paper of this issue highlights the historical changes in research priorities relating to cultivated pastures from the early 1900s and addresses key future research priorities in southern African pasture systems (Truter et al. 2015). Several matters relating to these priorities are subsequently addressed by other papers in the special issue. The environmental impact of cultivated pastures is a concern addressed by Swanepoel et al. (2015a). Widespread evidence of loading of soil with nitrogen, phosphorus, zinc and possibly other nutrients may have detrimental effects on environmental health. Mitigation strategies and fertilisation practices that prevent further loading should be prioritised (Swanepoel et al. 2015b). The authors identified soil quality assessment as potential means for adaptive soil management and for monitoring the effects thereof on ecosystem functioning and sustainability within pasture systems in the region. Using modelling to refine irrigation scheduling and nitrogen management will become more important in future, especially in the light of environmental management expectations in agricultural production systems. Abraha et al. (2015) explore the potential impacts of water and nitrogen management practices on productivity and forage quality of annual ryegrass. Diversification within cultivated pasture systems is another crucial factor for sustainability, although production needs to align with the demand for agricultural products. Muir et al. (2015) propose in a review paper not only that pasture productivity may be increased through diversified botanical composition, but there is an opportunity to diversify production of domesticated livestock and game species grazing cultivated pastures to achieve more resilient and sustainable grazing systems. Kikuyu (Pennisetum clandestinum), a dominant grass in cultivated pasture systems in southern Africa, has a number of characteristics that compromise long-term maintenance of high pasture productivity when other productive species are lost from pastures. However, diversification of the botanical composition by over-sowing with other grasses has potential to offer synergistic benefits for dairy pasture systems. Van der Colf et al. (2015a, 2015b) have evaluated complex dairy-pasture systems in the southern Cape region of South Africa and find potential to over-sow kikuyu pastures with annual ryegrasses with complementary growth patterns. Botha et al. (2015) further discuss the role of different ryegrass varieties in the fodder flow programme of dairy production systems. Lucerne (Medicago sativa) is arguably the most important legume in pasture systems in southern Africa, as it is a genetically diverse crop with higher production than many other forage crops across a range of climatic and edaphic conditions. Theron and Snyman (2015) report on the complexity of selecting the most appropriate lucerne cultivar, involving developing a cultivar ranking procedure to assist the pasture manager in selecting the most suitable cultivar for semi-arid regions. The research presented in this special issue will contribute towards a better understanding of potential to improve the productivity and efficiency of cultivated pastures in southern Africa. Several priorities for pasture research offer potential to provide required gains in productivity needed to maintain vital pastoral industries in southern Africa into the future.
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