Abstract: Lack of suitable storage facilities among smallholder farmers continues to expose farmers to intermittent food shocks. Farmers are thus making use of locally available preservation methods, derived from indigenous knowledge systems (IKS), to improve storability of sweet potatoes. However, not much is known about their efficacy in maintaining the quality of the stored crop. Thus the broad objective of this research was to assess the effectiveness of using soil, ash and grass as means of preserving sweet potato variety Mozambican White. The three mediums were tested over a period of 5 months and each treatment had two replicates. Three kilogram of soil, two kilogram ash and one kilogram grass were used for the analysis and the quantities were informed by local smallholder farmers. The experiment was conducted at ambient room temperature. Two parameters were monitored, the rate of discoloration of tubers and weight change over time. The results indicate that if quality of the stored crop and weight variation of tubers is considered, then use of soil banks is the most effective. However, weights of tubers for ash and grass were not statistically different from the soil treatment but some tubers were discolored. If farmers are to get the best results, a combination of the above techniques, particularly ash and soil, is recommended.
BACKGROUND AND PROBLEM
The bulk of developing countries in Africa are ensnared in abject poverty with individual households living on less than $1 dollar per day.  In addition, the HIV/AIDS pandemic has also ravaged social and economic systems of developing countries, thus compromising long-term economic development. Contemporary anecdotes reveal that at least 35 million people were infected by HIV/AIDS in Southern Africa in 2003. By the end of 2004, related estimates showed that 37.8 million people were infected by the scourge.  Thus it is not surprising that the gap between the rich and poor countries has been escalating over the last few years.
Although agriculture remains a key strategy to revitalizing the livelihoods of the rural poor, bottlenecks of major inputs such as fertilizers, chemicals and other synthetic inputs required for enhanced productivity remain a challenge for farmers and on household decision making vis-a-vis crop enterprise choice. Smallholder production trend indicate a shift in production patterns from the conventional crops such as cotton, maize and tobacco to other "unorthodox" crops which are less demanding in terms of input usage and labor requirements.  Crop enterprises such as indigenous vegetables and sweet potatoes are increasingly becoming an important option for the achievement of household food security in Southern Africa, including countries such as Zimbabwe. However, one of the major issues exposing farmers to chronic and transitory food shocks (particularly in the off-season), is postharvest loss. Studies indicate that postharvest loss due to pest and disease attack can account for as much as 40-60% of crop output.  Given that chemical-based systems of crop preservation are expensive for most farmers, least-cost preservation strategies need to be identified and there is not much literature on the efficacy of the various indigenous strategies to preservation.
In Zimbabwe, sweet potatoes are becoming an important component of the diet for both urban and rural households. For urban households, this has been necessitated by the escalating costs of bread and other starch-based foods such as Irish potatoes. Thus the integration of sweet potatoes should be considered as a rational coping strategy adopted by households to ensure food security. Sweet potato is an annual plant that thrives well under warm equatorial and tropical regions with hot summers. Taubenhouse (1989) noted that every buyer, grower, and storer of sweet potatoes has his own practices, theories, and beliefs about storing sweetpotatoes.  Therefore there is no universal method of managing postharvest losses. …