CBN-V Video Archives - S1-21
The Potential Advantages of Cassava over Hybrid Maize as a Food Security and Cash Crop in the Southern African Semi-Arid Zone

Robertson A.I. and T. Ruhode

Crop Science Department, PO Box 167 MP, Mount Pleasant, University of Zimbabwe, Harare, Zimbabwe ianzimcass@harare.iafrica.com

        The semi-arid regions of Africa are food-deficit areas with prevalent food insecurity. Cassava has virtually disappeared from Zimbabwe due to the success of hybrid maize in both communal and commercial situations. However, with the increasing availability of virus-cleaned cultivars, particularly M7 (marketed as Zambezi when virus-eliminated) and XM-6 (Limpopo) with which the potential yield is tripled from 8t/h to at least 24t/h, the achieved yields have triggered a re-examination of cassava as a potential food security crop and thereafter as a potential cash crop. It is proposed that modern management of elite cassava can offer a positive alternative to oft-failing hybrid maize or low-yielding traditional small grain production. Evidence will be presented to support three propositions. (a) Large stem pieces, when made available, planted during or before winter, establish large roots and establish successfully on zero precipitation over the first five months. With firm root establishment these then respond to heavy rains better than material planted with the onset of rains where roots can easily become waterlogged. (b) Two-node cuttings of elite virus-free cultivars, when given small amounts of supplementary water also establish and develop during the dry season and also respond quickly and vigorously when rains come. On-farm trials show that 24 t/h can be achieved on zero inputs. (c) Two-node cuttings given irrigation, fertiliser and careful management can generate a ten to twelve foot closed canopy and should form the basis of a much needed cash crop that takes advantage of this region’s high light regimes. On-farm trials showed sample yields of 40-60 t/h over twelve months. A fourth strategy involves spanning two rainy seasons. If cassava is planted just before the rains then yield in one year is low, but if the crop can be carried through to completing the second rainy season, then, even on extremely poor soils with low management backup, the yields can be 30-40 tons despite some damage from goats. Management of goats and other domestic animals is critical and can reduce yields to ten tons but, interestingly, increases the stem count (and so the abundance of planting material) from 1-3 branches to over 9-15. Similar yields can be achieved despite frost removing all leaves and some of the stems dieing back.

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