Crop production in KwaZulu-Natal/Annotated Bibliography/Sweet potato
Motsa, N.M., Modi, A.T. and Mabhaudhi, T., 2015. Sweet potato (Ipomoea batatas L.) as a drought tolerant and food security crop. South African Journal of Science, 111(11-12), pp.1-8. DOI PDF
Abstract: Sweet potato is an important 'indigenised' root crop in South Africa. It features prominently in smallholder cropping systems because of its versatility, drought tolerance and positive role in food security. It outranks most staple crops in vitamins, minerals, dietary fibre and protein content. Much information is available on sweet potato as a drought tolerant and food security crop, but critical reviews that link its drought tolerance with food security are lacking. We review sweet potato as a food security crop, focusing on mechanisms associated with drought. We conclude that the crop has great potential in the light of imminent challenges associated with drought as a negative effect of climate change.
Motsa, N.M., Modi, A.T. and Mabhaudhi, T., 2015. Sweet potato response to low-input agriculture and varying environments of KwaZulu-Natal, South Africa: implications for food security strategies. Acta Agriculturae Scandinavica, Section B—Soil & Plant Science, 65(4), pp.329-340. DOI PDF
Abstract: Three sweet potato cultivars (A40, A45 and 199062.1) were planted in three small-scale farms located under different agro-ecological zones of KwaZulu-Natal. The objective was to assess growth, physiological responses and yield of the sweet potato cultivars under low-input agricultural system and different environmental conditions. Sweet potato planted at Richards Bay (28°19'S; 32°06'E), a coastal sandy soil location, recorded low stomatal conductance(SC; 102.2 m moles m−2 s−1) and chlorophyll content index (CCI; 29.4). This consequently resulted in reduced vine length, leaf number and branching of sweet potato plants. Environmental conditions in that location (Richards Bay) such as high evapotranspiration, high temperatures and low water retention capacity of sandy soils created drought stress condition. This caused reduction in photosynthetic activities and translocation to the harvestable plant parts. The other two locations (Deepdale at 28°01'S; 28°99'E and Umbumbulu at 29°98'S; 30°70'E) located further from the coast and characterized by clayey soils recorded higher SC and CCI. Branching and number of leaves were significantly influenced by locations and growing season while vine length varied with locations, indicating specific varietal adaptation. Biomass and storage root yield followed a similar trend as plant growth and physiology. Richards Bay recorded very low biomass and storage root yield (5.4 and 5.0 t ha−1) in both seasons while Deepdale recorded higher yields (42.0 t ha−1) during the first growing season. Yields reduced by 67% (13.6 t ha−1) in the second season. Storage root yields from Umbumbulu were stable in both growing seasons (29.4 and 28 t ha−1 during seasons one and two, respectively). Adding fertilizer only improved storage roots yield in Richards Bay, otherwise cultural practises were responsible for storage root yield increases in Deepdale and Umbumbulu. Orange-fleshed sweet potato cultivar A45 showed good environmental plasticity while cultivar 199062.1 responded well to fertilizer application. This indicated its suitability for use in food security programmes under low-input agriculture.
Osborne, R., 2002. Sweet potato: A new look at an old crop with tremendous potential. KwaZulu-Natal Department of Agriculture and Environmental Affairs. Republic of South Africa, Pietermaritzburg. PDF
Sweet potatoes in KwaZulu-Natal produce similar yields to Irish potatoes but their management is less demanding. They have efficient root systems which can tolerate drought or low soil fertility better than potatoes. Sweet potatoes are also not subject to any serious foliar diseases, which makes spraying unnecessary. Sweet potatoes are highly nutritious, and have great potential to supplement subsistence diets. This two-page bulletin includes details regarding cultivars, climate and soil conditions, fertilisation, irrigation, weed control, pests, diseases and harvesting.