State of the Art of Yam Production

*Abukari Wumbei, Sopkoutie Kengni Nerlus Gautier, Joseph Kwowura Kwodaga, Djeugap Fovo Joseph and Yamdeu Joseph Hubert Galani*

### **Abstract**

Yam is a labor-intensive and weed-sensitive food crop. The labor-intensive nature of the yam means that the production process requires the attention of the farmer all year round. However, the dwindling labor situation and the proliferation of weeds have forced farmers to think of modern ways of controlling weeds on their farms, that is, the adoption of chemical (herbicides) weed control. Even though the adoption of these chemicals has no doubt brought relief to the farmers and has resulted in increased yam production over the years, it has also brought in its wake, negative externalities of environmental pollution, human health effects, and food quality issues. The study was thus designed to investigate how yam is produced, the human and environmental health effects of how yam is produced, and food quality effects of how yam is produced. This was done through literature review, and field and laboratory experiments. It was revealed that, in recent years, new innovations have been introduced in yam production, the manner in which farmers handle herbicides in their yam production process exposes them to high doses of pesticides, thereby endangering their lives. The study findings also suggest that the use of herbicides in yam production does not affect the quality of the yam.

**Keywords:** yam production, food security, Ghana, chemical herbicides and West Africa

### **1. Introduction**

Yam plants belong to the genus *Dioscorea* and produce tubers, bubils, or rhizomes that are of economic importance. They are monocotyledons in the family *Dioscoreaceae* within the order *Dioscoreales* which also includes the families *Stenomeridaceae,Trichoodaceae*, and *Stemonaceae*. In addition to the genus *Dioscorea*, the family also includes the genera *Stenomeris, Avetra,Trichopus, Rajana*, and *Tamus*. However, *Dioscorea* is by far the largest genus of the family [1].

Although more than 600 cultivars of the tubers have been recorded [2], only a few are important as staple food in the tropics. These include white yam (*D. rotundata*), yellow yam (*D. Cayenensis),* water yam (*D. alata*), trifoliate yam (*D. dumetorum*), aerial yam (*D. bulbifera*), Chinese yam (*D. po*lys*tachya*), and Lesser yam (*D. esculenta*) [1, 3, 4]. *D. rotundata* is a native to West Africa, but it does not occur in the wild, and it was probably developed from *D. praehensilis* Benth. The extent of its cultivation parallels the preference of the people of West Africa for this type of yam over most other kinds. Its cultivation has also spread to other parts of the world as it is grown extensively in the Caribbean, Asia, and South America [5].

West Africa accounts for over 90% of world yam production with Nigeria, the largest single producer followed by Ghana and Cote d'Ivoire [5, 6]. In 2016, global yam production stood at 66 million metric tons (MT) with 86% of this coming from West Africa. In 2016, more than 90% (6.9 million ha) of the global area under yam cultivation was in West Africa, where the mean gross yield is 12 t/ha [5].

Worldwide annual consumption of yams is 18 million tons, with 15 million in West Africa. Annual consumption in West Africa is 61 kg/person/year [7]. Yams are consumed in the form of boiled, roasted, baked, or fried. Yam is an important staple food for many Ghanaians, accounting for 28% of total calorie sources in 2016 [8]. Per capita consumption of yam in Ghana increased from 83 kg/year 1995 to 160 kg/person/year in 2013, making yam the second most important calorie source after cassava in Ghana [8, 9]. Between 2005 and 2010, yam production in Ghana contributed about 16 percent to the country's agricultural gross domestic product [6].

In Ghana, as in many other West African countries, the yam species of economic importance include *D. rotundata*, *D. alata*, *D. cayenensis*, and *D. bulbifera* [3]. Among these economically important species, it is *D. rotundata*, popularly called white yam or white guinea yam, which is grown on a larger scale than any other yam species in the dominant yam production zone of West Africa and Central Africa [7]. Several varieties of yam are produced throughout Ghana. These include Pona (white yam), Dente, Asana, and Serwa. In recent years, Ghana's Crop Research Institute (CRI) introduced new high yield varieties, such as the Mankrong and Kukrupa. However, white yam/Pona (*D. rotundata*) remains the most preferred variety in both the domestic and export markets [6].
