IK Monitor Articles (9-2)

Indigenous Knowledge and Development Monitor, July 2001

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Edwin M. Igbokwe

Between conservation and production: traditional ware yam cultivation in Igbo-Etiti, Nigeria

This study describes the practice of traditional ware yam cultivation carried out by smallholder farmers. The author concludes that farmers have many years of experience in managing resources and use this knowledge in the selection and introduction of cultivars that are adaptable to the farming system. In this way they have learned to adjust to an unfavourable environment so that they can continue to produce their major food crop.

As population pressures and the loss of fallow land force smallholder farmers in southeastern Nigeria into marginal lands, they endeavour to adapt to the new situation without degrading the land. In the loose sandlands or ferrasols they have adopted pitting and manuring methods suitable for raising yams. This has been followed by continuous trials in varietal selection to determine the best white yam (D. rotundata) for the system. This system deserves to be recognized by the extension services, because it is efficient and economical, and conserves both soil and water, making it capable of solving the agricultural problems of many land-hungry societies.

The rising population density, especially in southeastern Nigeria (range: 300-400, National Population Commission 1992) and the declining land-to-man ratio, the consequent predisposition of most agricultural lands to degradation, and the decline in fallow periods have driven most farmers into marginal states (Ruthernberg 1977). These new lands have been unable to support the farmers' staple food crops. As these factors impact on land-use intensification (Turner et al. 1993; Tiffen et al. 1994; Scoones et al. 1996), farmers have increasingly invested in new or borrowed technologies, thereby conserving the resource base and increasing their production (Scoones et al. 1996).

Some of the technologies are conservation-effective, and from the farmers' perspective provide direct benefits in the form of improved soil fertility and higher yields (Igbokwe 1999), as well as a lower erosion rate and better soil moisture conservation (Douglas 1994). These technologies amount to 'nutrient husbandry' (IITA 1992) without external inputs. In the highly erodible and less productive ferrasols of southeastern Nigeria, farmers have been forced to experiment with yam production in planting pits or trenches filled with organic manure and waste material. Although the practice is not actually new, it was originally confined to 'compound farms' (Onwueme 1978; Diehl 1982). A significant new development is that in Igbo-Etiti the practice has been adopted on a large-scale in less productive distant farmlands.

This study describes the practice as carried out by smallholder farmers (30 male heads of households) in two communities, Aku and Lejja in Igbo-Etiti, Enugu State, Nigeria.

The study area
Igbo-Etiti is one of the sub-ethnic and local administrative areas inhabited by northern Igbos in the Nsukka agricultural zone. With a total population of 131,669 (National Population Commission 1992) and a population density of 395 persons/km2, the area exhibits demographic characteristics similar to other Igbo areas. Lying between latitudes 6o30' and 6o47'N and longitudes 7o16' and 7o50'E, it is made up of 13 communities. Annual rainfall ranges between 1600 mm and 1800 mm from March/April to October and is reliable and plentiful enough to support a wide variety of crops. The vegetation consists of secondary savanna woodland on rolling land punctuated by isolated hills and homestead palm groves. Much of the area falls within the Nsukka sandlands (ferrasols), except around Aku, where some clay occurs in the valleys (Grove 1951).

Farming system in Igbo-Etiti
Agriculture in Igbo-Etiti is rain-fed, so that during the dry season all farm activities cease except for the period January to March, when land clearing and the digging of yam planting holes or trenches commence. Most farmers or household heads maintain home gardens (ani-ulo) with an average size of 0.2 ha. These are heavily manured, being close to the house, and crops such as yam (Dioscorea spp.), cocoyam (Colocasia and Xanthomonas spp.) maize (Zea mays) and various legumes and vegetables are grown singly or in combination in the shade of economic trees, such as oil palm, kola, ivingea and oil bean.

Beyond the living areas are distant farmlands (ani-agu), most of which are marginal lands, until recently devoted to growing cassava. In general the cropping system of the area may be described as yam-based: every male-headed household endeavours to grow yams because of the strong ethnocentric attachment, the premier position yam occupies in the hierarchy of crops (Okorji and Obiechina 1993), and other factors of sociocultural significance. This has led some male heads of households to temporarily migrate westward, to rich lands in the Anambra/Niger river valley around Uzo-Uwani and Igalaland, in order to cultivate yams.

Most households also keep livestock, such as sheep and goats (usually only one), which graze on rough pasture in uncultivated land and are housed during the night. These animals - and to some extent the dwarf cattle - also provide manure for yam production.

Yam production
Land preparation involves the digging of pits or holes and rectangular trenches, using hoes. The holes are 30-40 cm in diameter and 30 cm deep, and generally 1 m apart. The trenches vary in length, depending on the size of the farmland, but the width is usually 40-50 cm. The former is more common in distant farmlands (ani-agu), but the choice is up to each individual farmer.

When opening up new lands, digging commences in October/November, since the soil is wet and digging is easier. It is also a slack period in the farming calendar, when the cost of labour is low. In older plots, pits or trenches are opened up between December and February, after harvesting.

The manuring of the pits starts almost as soon as digging is completed. In the first phase, dry palm leaves and Acioa barteri leaves are laid in the holes. Household garbage is subsequently collected and spread over the leaves. This activity continues up to the end of March, when the early rains are expected. After the rains, the leaves and garbage are burnt. In the more southern areas of the region, which are wetter, the organic materials are not burnt, because decomposition is completed before planting commences. Meanwhile, organic manures such as sheep, goat and cow dung, and compost are dug up from the manure sheds and spread on the soil after it has been dug. The manure is mixed with the soil and used to fill up the holes. After levelling, the remaining mixture is used to build a low mound or ridge over the hole or trench.

Planting follows in a few days, depending on the amount of moisture produced by the early rains. 'Seed' yams (small whole tubers weighing 250-400 g) of the white yam species Dioscorea rotundata are commonly grown. However, not all the cultivars of the white yam and other species are suitable for the pitting and manuring system (see Table 1).

Table 1: Commonly grown yams in Igbo-Etiti, Nigeria.

Three cultivars of D. rotundata (aba, obialu and nwocha) are grown by this method. Yam setts (slices of tuber) are rarely used, since without chemical treatment the cut surfaces predispose them to drying, pests and disease, and yields have proved to be lower. The seed yams are sown at an angle and then covered with a layer of soil 7-10 cm deep. For pregerminated seed yams, which are generally preferred, the tender vines are ringed with thick leaves of Agave sisalana or Sansevieria spp., to prevent desiccation. Dry palm leaves and grasses are used for mulch, to counter the heat of the sun, which is intense at this time of year. The selection of yam cultivars is an on-going process among these farmer-innovators. For example, the cultivar Obialu - whose name reflects its recent emergence - comes from Uzuakoli, an Igbo community about 300 kilometres away. Nkwocha was first grown in Affa, a community about 40 kilometres away, but dates from an earlier period.

Harvesting
Early harvesting of ware tubers begins in late July and early August. There are three major reasons for early harvesting. First, this is a lean period in the food cycle and farmers can maximize profit by getting their produce into the market now, rather than during the main harvest season in December/January. Second, seed yams constitute over 50% of the cost of production, which means that it is important to produce secondary tubers that can be used for the next planting. This is done by digging up the tuber, carefully cutting off the crown to avoid damaging the roots and vine, and replanting the crown. And finally, it is a common belief that tubers produced in sandy soils do not store well and the heavy use of organic manure tends to speed up the rate of damage by pests and diseases, especially beetles and nematodes. For this reason, efforts are geared toward early harvesting and sale. Ware tubers weighing as much as 8.5 kg (wet weight) are widely obtainable. The average yield is 10-12 tons per ha, which is comparable to yields on richer soil set aside for yam production. Moreover, the system is economical, because the same holes or trenches are manured and planted year after year, with no loss of yield. Moreover, burning tends to eliminate nematodes, which constitute a major impediment to the continuous cropping of yam on the same plot.

Conclusion
Over the years farmers have learned to adjust to an unfavourable environment so that they can continue to produce their major food crop. This effort involves a meticulous soil and water conservation technique that enables them to grow yams in an otherwise unsuitable soil. Moreover, as experimenters, they are continuously involved in the selection and introduction of new cultivars that can be adapted to the traditional farming system. The knowledge which is inherent in these practices derives from many years of experience in the management of natural resources. Extension services should recognize the advantages of this practice, which is efficient and economical and conserves soil. That could be the beginning of a move to disseminate these methods among other farmers who are likewise being pushed onto marginal lands, and are thus unable to rely on the traditional mound-making system in a more suitable environment.

Edwin M. Igbokwe
Department of Agricultural Extension
University of Nigeria,
Nsukka University of Nigeria, Nsukka, Nigeria
E-mail: syskraft@hyperia.com

References
Diehl, Lothar (1982) Smallholder farming system with yam in Southern Guinea Savannah of Nigeria. Germany: GTZ.

Douglas, M. (1994) Sustainable use of agricultural soils. Berne, Switzerland: GDE, Institute of Geography, University of Berne.

Grove, A.T. (1951) Land use and soil conservation in parts of Onitsha and Owerri Provinces. Lagos: Nigerian Government.

Igbokwe, E.M. (1999) 'From process to innovation: land use intensity among smallholder rice farmers in Eastern Nigeria.' Indigenous Knowledge and Development Monitor 7(1): 3-7.

IITA (International Institute of Tropical Agriculture) (1992) Sustainable Food Production in Sub-Saharan Africa 1. IITA's contributions. Ibadan, Nigeria.

NPC (National Population Commission) (1992) Census News 3(1).

Okorji, E.C. and C.O.B. Obiechina (1993) 'The role of seed yam procurement arrangements in the smallholder cropping system of Anambra State, Nigeria'. African Development Review 5(1): 70-80.

Onwueme, I.C. (1978) The tropical root crops. New York: John Wiley.

Ruthernberg, H. (1977) Farming systems in the tropics. Oxford: Clarendon Press.

Scoones, I., C. Reij and C. Toulmin (1996) Sustaining the soil: indigenous soil and water conservation in Africa. London: Earthscan.

Tiffen, M., M. Mortimore and F. Gichuki (1994) More people, less erosion: environmental recovery in Kenya. Chichester: John Wiley.

Turner, B., G. Hyden and R. Kates (eds.) (1993) Population growth and agricultural change in Africa. Gainsville: University of Florida Press.

Photographs and Websites that may interest readers of this article.