Yam (Dioscorea species) is a perishable tropical crop plant that produces edible tubers rich in carbohydrates with low protein content. The major species are particularly indigenous to West Africa, and were the major sources of carbohydrate before the introduction of exotic crops including maize, rice, and cassava [1] [2]. Yam belongs to the genus Dioscorea which contains about 600 species [3] [4]. Of these species of the genusDioscorea, Dioscorearotundata (white yam), Dioscoreaalata (water yam), Dioscoreacayenensis (yellow yam), Dioscoreabulbifera (aerial yam), Dioscoreaesculenta (Chinese yam), and Dioscoreadumetorum (trifoliate yam) are cultivated in the light sandy soils of the interior savannah and in the forest zone of Ghana [5]. Besides the cultivated yam species, there are a number of wild types which are also harvested for food. The commonest of these is the Dioscoreapraehensilis which is common in the forest belt.

The white yam, yellow yam, and water yam are the most important in West Africa as a source of food and are grown almost to the total exclusion of the rest except aerial yam which together with other minor species receive limited attention. The aerial yam and the Chinese yam are less important in the sub-region [6]. The white yam is the most widely cultivated [7] [8] and it is also the most popular. White yam is the principal commercial yam and constitutes about 80% of the total yam produced in Ghana. Water yam is also cultivated commercially in Ghana but to a lesser extent than the white yam [5] [7]. Few farmers grow yellow yam, aerial yam, Chinese yam, and trifoliate yam and it’s mainly for home use. Zaknayiba and Tanko [9] noted that among the species, several varieties exist and Ackah et al. [5] observed that “Laribako” and “Puna” varieties of white yam are preferred and highly priced in Ghana. “Laribako” and “Puna” varieties have also been exported in Ghana (M. Abu, pers. Commun.) [10].

Kwara [11], Djana et al. [12], and earlier reports by FAO [13] indicated that factors that influence the choice of varieties of yam that farmers grow include consumer taste preference, maturity, storability, yield, adaptability, and availability and cost of planting materials. These sources also indicated that constraints to yam production include high labour demand for most cultural operations and other inputs such as planting materials, unreliable sources of credit, pests and diseases, declining soil fertility, and unpredictable weather conditions.

Even though current estimates of world-wide yam production output are far from complete or reliable [2], Africa is reported to have been responsible for about 95% of the world output with Nigeria remaining by far the largest producer in the continent. Ghana however remains the fourth largest producer. In Ghana, production growth rate for yam is projected to be 2.75% per annum [5]. The main centres of yam production in Ghana are the districts of Kwahu North (Eastern region); Sene, Kintampo, Atebubu, and Techiman (Brong-Ahafo region); Kete-Krachi and Nkwanta (Volta region); Ejura and Sekyedumase (Ashanti region); Salaga, Bimbila, and Sang (Northern region); and Wa and its environs (Upper West region). Yam is produced in many more districts but not in commercial quantities as in the named districts. Brong Ahafo, Northern, and Eastern regions are the high yam production areas in Ghana. The Brong Ahafo region is the leading producer of yam in Ghana both in terms of physical production and acreages cultivated. But the Nanumba North District yam production area of the northern region of Ghana hosts larger production of “Laribako” and “Puna” varieties of the white yam which have been reported to be preferred, highly priced, and exported in Ghana (M. Abu, pers. Commun.) [14].

Rees [14] reiterated that yam is the most important of the farm crops produced for home consumption in the internal economy of the people in the Nanumba North district, and they also earn foreign exchange. Only one cropping season is possible during the year, and it is therefore necessary to store yam to cover the lack period and for other domestic and commercial purposes. It is also reported that there is under improvement of the yam crop; a situation that is accentuated by persistent deterioration as a result of lack of knowledge on the causes associated with yam health disorders [12]. Also, despite the fact that yam has an important role to play in meeting the food needs of the rapidly increasing human population and ensures food security in Ghana coupled with its income generating capability and export potential, very little attention has been given to its health care during storage. Farmers therefore continue to lose substantial parts of their stored produce as a result [11] [14].

In Ghana, the production and healthy storage of the perishable yam on both small and large scale 1) is an addition to other major carbohydrate containing crops such as maize, rice, and other root and tuber crops 2) generates jobs in the urban and peri-urban areas, 3) enhances the potential of horticultural crop export in Ghana, 4) may reduce foreign exchange requirements for imported carbohydrate-based foods, and 5) may also contribute positively to the National Poverty Reduction Drive [15] [16]. Yam is among the most important food crops and has economic and sociocultural importance in Ghana [2]. The fresh yam tuber contains an appreciable quantity of vitamins and minerals and it is also a source of industrial starch [9]. Yam’s significant contribution to the food security in the sub-region has been well documented [3]. It serves as vital sources of calories especially in Bénin, Côte d’Ivoire, and Ghana. Yam also features prominently in social rites of passage, and thanks giving in the region. Its production is seasonal and the fresh tubers are highly perishable. Zaknayiba and Tanko [9] reiterated that postharvest losses are very high, ranging from 30% to 85% of the total production. In order to overcome this high perishability of the tuber and the irregularity of its availability throughout the year, investigating and making recommendation(s) for the development of technologies that result in improved/enhanced storage of each kilogram of yam becomes a necessity. This would greatly ameliorate problems faced by yam producing households, thus reinforcing food security and possible export. Hence, the need to investigate into and ascertain the possible cause(s) of health disorders encountered during storage of yam at farm gate in the Nanumba North district yam production zone in Ghana with the following objectives:

1) to identify, sample, and determine the background of respondents,

2) to determine the types/varieties of yam cultivated and the associated production characteristics,

3) to assess the agronomic and harvesting practices (in relation to yam health),

4) to assess the storage and marketing technologies practiced (in relation to yam health) by the yam farmers.

A survey was carried out in some selected major yam producing areas in the Nanumba North District of Ghana to investigate possible cause(s) of yam health disorders while in storage at farm gate. This was accomplished by administering questionnaires to the yam production sector of the yam industry in the study area. In all, hundred (100) respondents were interviewed.

Farmers in the study area were quite old with majority of them falling within the ages of 31 - 40 years (34%) followed by 41 - 50 years (30%). This result was in line with the findings by Hudu et al. [16] and Kwara [11] who reported that yam farmers in the North Eastern corridor of Northern Ghana were quite old with a mean age of 40.48 years. All respondents were males which confirm early findings by Adam et al. [15] and recently by Kwara [11] who reported that yam production in Northern Ghana was a male dominated enterprise with a probable reason that yam production was more labour intensive when compared to the production of other crops. Djana et al. [12] reported that not all available family labour was involved in yam production but that men were more involved when investigations were conducted in Ghana and Nigeria.

Majority (44%) of the farmers did not have any form of education and only twelve percent (12%) made it to the tertiary level whiles the rest were found between basic and senior high school levels. The results showed a high level of illiteracy among yam farmers in the area. Adam et al. [15] reported earlier that the educational status of farmers in the North eastern corridor of Northern Ghana was highly illiterate and further opined that such high illiteracy may have a significant impact on the levels of adoptions of new technologies in yam production.

Laribako, Limo, Fuseini, Prinjo, Nawari (water yam), Alando, Akaba, Baatoo, Nyame-Nti, Afayili, Baffoo, and Pona varieties/cultivars of yam were discovered in the study area. This discovery was reiterated by Kwara [11] who also stated that the names of the cultivars as indicated were only recognised by the people of a particular geographical location and could be known by different names elsewhere. The most popular varieties were Laribako, Fuseini, Alando, Prinjo, and Nawari which were mostly cultivated in combination with others on the same farm. Cultivating one variety alone on the same farm was unusual among the farmers. The choice of these cultivars was influenced by the availability of the cultivar, high yielding ability, and market demand (with particular reference to taste and appearance) [12]. Barnabas [19] and Amegbeto et al. [20] indicated that consumer preference may help in designing new crop varieties and crop management systems that simultaneously satisfy the needs of farmers and the consumers alike. The authors added that it may also aid in the determination of relevant quality attributes of the product as asserted by Zaknayiba and Tanko [9].

Majority of the farmers indicated that they used their own monies in farming but was usually insufficient; a situation that could result in absence of adequate funding for required farm inputs. Agricultural extension services officers visited the farmers quite irregularly with the consequence of a few or no extension officer-farmer interactions which would have informed the low rate of adoption of technologies amongst respondents. Majority of farm sizes were in the range of 6 - 10 hectares per head and labour availability turned out to be a major problem but contrary to this, Djana et al. [12] reported that hired labour for yam production was prominent in Ghana and Nigeria. Majority of the farmers used their own yam sets than purchased or certified yam sets following reports by Djana et al. [12] who stated that farmers in Ghana and Nigeria mostly used own-produced yam sets. The authors attributed this to unavailability or cost of the yam sets and that the consequences could be low productivity.

Zaknayiba and Tanko [9] reported that yam is produced in Ghana with unsophisticated inputs. This is demonstrated by little or no usage of sophisticated inputs in this study, probably due to unavailability of new technologies, cost of equipment, or farmers’ poor attitude towards adoption. All farmers prepared mounds for yam production which they believed enhanced larger and quality tubers. Staking and weeding were their common practices after planting which were said to be necessary for optimal exposure of the yam plants’ leaves to sunlight for healthy plant growth and productivity, more especially in yam varieties with climbing vines [4].

Harvesting was done at any time of the day with common simple tools like cutlasses, hoes, earth chisels, and sticks but with problems of cuts, punctures, and abrasions on vulnerable tubers. Curing was not done after harvesting which may have led to the rotting of tubers encountered during the study. Curing is essentially a wound healing operation to replace the damaged periderm prior to storage of yam. Yam tubers therefore need to be properly cured according to recommended procedures as soon as possible after harvest to enable the formation of a cork layer over the surface for protection against micro-organism infection and excessive water loss which enhances shelf life of the tuber [21].

Majority of the farmers’ yam produce, particularly on commercial scales were sold to middle men in the resident market. Due to high cost of transportation as influenced by bad road networks and associated problems, farmers found it difficult transporting their produce to the urban market centres where demand was high. Barnabas [19] indicated that transportation played an important role in the distribution of agriculture produce in Ghana and that it helped in creating market for agriculture produce and reduced spoilage and wastage of farm produce.

In the rainy season when fresh yam is harvested it is stored in shallow trenches but for temporal purposes. For dry season when more yam is harvested, majority of the farmers store for up to 6 - 7 months in barns and on wooden platforms: the barn being the most preferred in West Africa [21] [22]. Yam storage techniques seem to be limited among the farmers and may be due to insufficient services of agriculture extension officers. Farmers need to understand that only sound and healthy yam tubers are suitable for storage. As a result of this yam is harvested with great care but because of its perishable nature some will get damaged accidentally and need to be isolated for curing or put to immediate use. Farmers suffered technological knowledge gaps since none of them seemed to be aware of curing of yam, the use of chemical or botanical treatments, and other storage techniques or procedures for the yam tuber prior to storage.

Ages of respondents were in the range of 11 to over 60 years with illiterate majority which was a threat to productivity. They were inadequate in their knowledge on agronomic, harvest, and postharvest practices and techniques that enhance health and shelf life of yam.

Farmers suffered technological knowledge gaps since none of them seemed to be aware of curing of yam, the use of chemical or botanical treatments, and other storage techniques or procedures for the yam tuber prior to storage. They kept their fresh yam produce in shallow dug trenches where temporal storage was the target but stored their dry yam produce intended for long periods in barns (most preferred) and on wooden platforms. Barns and wooden platforms were more sustainable but with a little preponderance of the former.

Causes of health disorders and associated problems in store were insect pests, rodents, weed pests, diseases/tuber rot, yam beetles, snakes, scorpions, and the inability of some storage structures to keep produce for a long time.

Research, government, and other stakeholder institutions should partner up and make improved and certified yam sets accessible and affordable, and intensify agriculture extension services’ interventions that empower farmers the knowledge on agronomic, harvest, and postharvest practices and techniques.

The authors are thankful to the farmers who were willing to participate in the study.

The authors declare no conflicts of interest regarding the publication of this paper.

Abu, M. and Adzigiwe, K.F. (2021) Possible Causes of Health Disorders in Stored Yam at Farm Gate. Agricultural Sciences, 12, 960-976. https://doi.org/10.4236/as.2021.129062