Abstract To assess the symbiotic dependency of grain and shrub/tree legumes within five agro-ecological zones of Botswana, fully expanded leaves of the test species were sampled from about 26 study sites within Ngwaketse, Gaborone, Central, Ghanzi and Kalahari agro-ecological zones. Isotopic analysis revealed significant differences in 1)15N values of the grain legumes [cowpea (Vigna unguiculata L. Walp), Bambara groundnut (Vigna subterranea L. Verde.), and groundnut (Arachis hypogaea L.)] from the 26 farming areas in both 2005 and 2006. Estimates of %Ndfa of leaves also showed significant differences between farming areas, with cowpea deriving more than 50% of its N nutrition from symbiotic fixation. In terms of distribution, many more symbiotic shrub/tree species were found in the wetter Ngwaketse agro-zone compared to the fewer numbers in the drier Kalahari region. Acacias were the more dominant species at all sites. Leaf 1)15N values of shrub/tree species also varied strongly across Botswana, with 11 out of 18 of these legumes deriving about 50%, or more, of their N from symbiotic Nz fixation. Acacia caffra, in particular, obtained as much as 93.6% of its N nutrition from symbiotic fixation in the wetter Ngwaketse agro-zone. This study has shown that grain legumes sampled from farmer's fields in Botswana obtained considerable amounts of their N from symbiotic fixation. We have also shown that shrub and tree legumes probably play an important role in the N economy of the savanna ecosystems in Botswana. However, the decline in the number of functional Ny-fixing shrub/tree legumes along an aridity gradient suggests that soil moisture is a major constraint to Nz fixation in the tree legumes of Botswana.

Abstract To assess the symbiotic dependency of grain and shrub/tree legumes within five agro-ecological zones of Botswana, fully expanded leaves of the test species were sampled from about 26 study sites within Ngwaketse, Gaborone, Central, Ghanzi and Kalahari agro-ecological zones. Isotopic analysis revealed significant differences in 1)15N values of the grain legumes [cowpea (Vigna unguiculata L. Walp), Bambara groundnut (Vigna subterranea L. Verde.), and groundnut (Arachis hypogaea L.)] from the 26 farming areas in both 2005 and 2006. Estimates of %Ndfa of leaves also showed significant differences between farming areas, with cowpea deriving more than 50% of its N nutrition from symbiotic fixation. In terms of distribution, many more symbiotic shrub/tree species were found in the wetter Ngwaketse agro-zone compared to the fewer numbers in the drier Kalahari region. Acacias were the more dominant species at all sites. Leaf 1)15N values of shrub/tree species also varied strongly across Botswana, with 11 out of 18 of these legumes deriving about 50%, or more, of their N from symbiotic Nz fixation. Acacia caffra, in particular, obtained as much as 93.6% of its N nutrition from symbiotic fixation in the wetter Ngwaketse agro-zone. This study has shown that grain legumes sampled from farmer's fields in Botswana obtained considerable amounts of their N from symbiotic fixation. We have also shown that shrub and tree legumes probably play an important role in the N economy of the savanna ecosystems in Botswana. However, the decline in the number of functional Ny-fixing shrub/tree legumes along an aridity gradient suggests that soil moisture is a major constraint to Nz fixation in the tree legumes of Botswana.

Development, environmental sustainability, agriculture and livelihoods are dimensions that are often considered antagonistic. By thinking at the landscape level however, innovative opportunities arise for simultaneity as these entities manifest spatially and require communication across disciplines. Trans-frontier Conservation Areas (TFCAs) embrace this thinking. These are large areas that cut across two or more international boundaries, include within them at least one Protected Area (PA) and other multiple resource use areas, including human dwellings and cultivated areas. Similarly, ecoagriculture is an innovative approach to land use management as it seeks to spatially synergise agriculture, livelihoods and biodiversity conservation across space and requires an awareness of landscape-level issues by land users, a condition which is not necessarily met. Such landscape thinking stems from the fact that if a piece of land is subject to rigorous conservation, it will fail if the surrounding areas are degraded. Additionally, it has been shown that agriculture often benefits from the nearby presence of natural areas for ecosystem services such as pollination, pest management, and erosion control. As such, multifunctional landscape mosaics together with small scale farmers, not large scale monocultures, are the key to global food security, as the former more effectively links agricultural intensification to hunger reduction. In order to ascertain an integrated understanding of the landscape concept, necessary for the formalisation of ecoagriculture, this study assessed the landscape perceptions and understandings held by local people residing within a TFCA. We employed participatory methods within the Mathenjwa Tribal Area (MTA), an area falling within the Lubombo TFCA and identified as holding ecoagriculture potential. Results revealed that local people perceive landscape as a function of subsistence utility. Local people perceive land-use multifunctionality, necessary for the formalisation of ecoagriculture, but at a smaller scale than expected depending on both social and biophysical interpretations. Landscape scale projects should incorporate local landscape understandings. / Dissertation (MA)--University of Pretoria, 2013. / Geography, Geoinformatics and Meteorology / MA / Unrestricted