2.4.1 Demographic information
The majority of the 345 farmers interviewed were women. Most of the women had 1-5 children; the majority of the female farmers aged 21-40 and many household had children aged 0-10 years. This indicates the need to promote growing of OFSP as a source of vitamin A especially for the children aged 3-10 years and the lactating mothers in these households. In many households men are the head and decision makers even concerning farming activities. However, most of the men work and reside in the urban areas, which explains why the majority of the farmers interviewed were women. The absence of men on the farms causes delays in decision making which in turn causes delays in farm preparation and planting and consequently contributes to poor yields. Considering both gender, most farmers were aged between 41-50 years. This could be explained by the tendency of young
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people moving to urban centres in search of work after finishing school/college. The majority of the household farm sizes were also small with sweetpotato grown on 0.5 acres and below. Results from this study were in agreement with those reported by Shonga et al.
(2013) who reported that farmers grew sweetpotato on characteristically small sized plots in Ethiopia. This is because farmers try to produce enough for subsistence use, because there is no long term storage method for sweetpotato after harvesting. If the sweetpotato crop is ready for harvesting, leaving storage roots un-harvested will result to considerable losses as they lose their quality and are typically infested heavily by weevil. Similar findings were reported by Mmasa et al. (2012) in Tanzania who further recommended the increase of land area under sweetpotato production in order to boost productivity.
2.4.2 Food and cash crops, and sweetpotato varieties
Farmers classified almost all the food crops also as cash crops. Many of the farmers interviewed used part of their produce for food and sold the rest to generate cash income.
However, increased commercialization of the crop and the fact that supermarkets and hotels are retailing sweetpotato storage roots and French fries is an indication that sweetpotato is a potential cash crop, which farmers could produce in large scale for income generation.
The varieties Vitaa, Kembu 10, and Kabonde were grown by most of the farmers. These varieties have high beta carotene and thus are used as health foods. Moreover, sensitization of orange fleshed sweetpotato as source of vitamin A has created a demand for these varieties, hence generating market. Moreover, this also shows that farmers were receptive to improved and released varieties compared to local landraces.
2.4.3 Cultural practices
Sweetpotato planting materials were mainly recycled from the previous crop, since only a very small portion of the farmers indicated they used certified planting material. This shows that either most farmers do not understand the importance of using clean and certified planting materials or do not have an alternative. This partially explains why sweetpotato yields continue to be low. Fuglie (2007) conducted survey work on sweetpotato constraints across many countries, and similarly found that lack of clean and enough planting material was a major constraint in most of African countries. In this study, farmers preferred to use manure rather than inorganic fertilisers such DAP and NPK, while a large number of farmers did not use any fertiliser. The farmers believe inorganic fertiliser makes the sweetpotato grow vegetatively and results in tasteless storage roots. Some believe that sweetpotato does not require a lot of soil nutrients and thus would do well with low soil fertility. These arguments may not be too far from the truth; however, research is required towards the development of a fertilisation model that improves the yields of sweetpotato but maintaining
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the palatability qualities. Most farmers used ridges in planting sweetpotato, probably because this planting method leads to better yields than the other types of cultivation (Githunguri and Migwa, 2007). Mixed cropping with other food crops was the most preferred method, meaning farmers prefer planting crops in a mixture to spread the risk of failure to harvest in case of drought or any other unexpected constraint. However, some farmers planted sweetpotato as a monocrop, which suggests that the perception of the farmers on the value of the crop is changing.
2.4.4 Sweetpotato planting material conservation method
Most farmers leave the sweetpotato planting materials in the field. Consequently, the materials are heavily infested with virus and other pests and diseases. The aftermath is a reduction of the yield by 50% relative to the previous crop. These results are similar to those reported by Namandaa et al. (2013) who demonstrated that sweetpotato planting material sourced from swamp or irrigated on farm plots were infested with virus and getting it from volunteer plants after rains led to planting delays. In this study, roots conserved under sand and planted 10 cm deep and watered for 5-10 weeks before the onset of rains produced enough clean planting materials at the onset of the planting season. There is significant need to develop a working system of developing clean and enough planting materials for sweetpotato ready at the onset of the rains. Most farmers preferred higher planting densities, that is, 75 x 30, 60 x 60 and 75 x 60 cm, indicating a preference for intensive farming to maximise the productivity of their scarce land. This is supported by Belehu (2003) who reported that high density resulted in increased yield of sweetpotato. Also, higher density planting suppresses the weeds and at the same time minimises evaporation of soil moisture, resulting to improved yield (Kivuva et al., 2005)
2.4.5 Sweetpotato yields
Most sweetpotato yields on-farm ranged 5.5-7.4 t ha-1, which is below the average production of 9 t ha-1 in Kenya. Shonga et al. (2013) in their review on sweetpotato production constraints reported average sweetpotato yield in Ethiopia of 8 t ha-1 relative to 18 t ha-1 in the Asian countries. This indicates production constraints need to be addressed to improve the productivity of the sweetpotato.
2.4.6 Sweetpotato production constraints and coping strategies
Most farmers identified drought associated with hard soil pan, lack of clean and enough planting material and high cost of inputs as major constraints for land preparation and planting. Shields and Fletcher (2013) reported similar results in Uganda. This calls for researchers to devise methods of breaking the soil hardpan, and production of enough and clean sweetpotato planting materials. Breeding drought tolerant varieties, especially the
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deep rooted, may also minimise storage root yield losses due to soil surface hard pan and weevil infestation. This also concurs with Mmasa et al. (2012) who reported shortage of planting material, lack of capital, drought and pests and diseases as sweetpotato production constraints in Tanzania
The major constraint experienced during harvesting was drought. Thus there is need for ways of simplifying harvesting when terminal drought occurs making the soil surface hard to break. Irrigating the field softens the soil surface and simplifies harvesting. Also, use of oxen and tractors would simplify the harvesting, hence, reduce root damages during harvesting.
But these practices are not readily available to poor farmers. Research is also required for the best way to effectively control moles that cause damage to sweetpotato storage roots.
Farmers engage the services of skilled mole trappers, which is expensive to sustain.
Most farmers in this study identified weevils as a major pest and sweetpotato virus disease (SPVD) as a major disease affecting their crop. This concurs with Ngailo et al. (2013), who reported that SPVD reduced yields 50-80% in Tanzania. They also indicated that the cheapest control method for the resource poor farmers was breeding for resistance. In this study, most farmers used unconventional weevil control methods such as manure application, which improves soil structure and irrigation which reduced the soil cracking and thus reduced the weevil infestations. This is similar to results by Ehisianya et al. (2013 ) in Nigeria who reported that a mixture of 50 ml of neem seed oil extract and 30 ml of diazinon in either 2 or 10 litres of water and cuttings dipped for 30 minutes (unconventional weevil control method) controlled Cylas puncticollis by 35.5%. However, data collected also showed a number of farmers were ignorant of pests and diseases that affected sweetpotato.
This implies that there is need to sensitize farmers on diseases and other aspects of sweetpotato. Degu et al. (2013) also reported the need to improve the capacity for farmers to take up and continue with developed varieties and technologies. The lack of resistant varieties as well as disease and pest free sweetpotato planting materials were the major hindrance to pest and disease control. Thus breeders need to identify resistant varieties as well as promote production of clean seed to improve sweetpotato production. This is in agreement with results of work done on resistant gene expression on sweetpotato virus resistance (McGregor et al., 2009). Furthermore, Tefera et al. (2013) have also reported SPVD as a major constraint of sweetpotato production in Ethiopia. They also, reported that Alternaria blight was a constraint even though not serious, which concurs with the findings in this study.
As coping strategies some farmers indicated used clean planting materials, and improved varieties tolerant to drought, pests and diseases in order to have improved yields. This
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implies that farmers are willing to embrace research technologies aimed at improving sweetpotato production.