熱帯焼畑農業の二類型

西アフリカ,ナイジェリアの事例を中心として

抄録

The swidden agriculture is widely distributed in the tropical zone. Its distribution seems to have been already clarified by D. Whittlesey. As it is well known, D. Whittlesey had classified this tropical native agriculture as two types: shifting cultivation and rudimental sedentary tillage.
Nevertheless, according to the recent scientific results his two types are not always considered to be suitable to explain the tropical native agriculture. (Refer to Morgan, W.B.: Agriculture in Southern Nigeria, Econ. Geogr. Vol.35, 1959). Furthermore, among the researchers there are so diversified appreciation about the swidden agriculture that a scientific tendency has been brought on to seek after certain new type in the swidden agriculture in the tropics. For example, Komei Sasaki, having located many principal treatises of tropical swidden agriculture in the history, has suggested the two types concept in the Human Geography (The Jimbun-Chiri) Vol.17, No.6, 1965.:
1) Millet cultivation type brought about in the Savanna environment
and
2) Root cultivation type in the Rain Forest environment. Including Sasaki's concept most of the tropical swidden agricultural studies had been mainly centered upon the crop complex as well as upon the crop rotation system. Really they are mere one partial concept of the agriculture, and in such studies, we should say, they are touching to the agricultural complex rather at the standpoint of time than at its spacial side. Primarily doing of agriculture is embodied in cultivation of the ground. In this sense it is not to be approved that the concept of types centering upon the crop complex and the crop rotation system has enough ground to rely on.
Therefore, in this treatise, I would like to investigate these types in touching to the crop rotation system at the standpoint of time and simultaneously to the land use pattern from the side of space. In other words, I am going ahead with my studies upon the relation between the crop rotation system and the land use pattern at the unit of village. I picked up as my research field Nigeria, West Africa, where presents a sharp contrast between the Savanna environment and the Rain Forest environment.
According to the concept of the swidden agriculture in West Africa there are counted 9 kinds of the staple subsistence crop: Fonio Digtaria exilis, Maize Zea mays, Pearl Millet Pennisietnm typhoideum, Sorghum Sorghum spp., Finger Millet Eleusine coracana, Manioc Manihot utilissima, Taro Colocasia antiquorum, Yam Dioscorea spp., Plantain Musa sapientum, M. paradisiaca.
Most extensively distributed cereals in Western Africa are Pearl Millet and Sorghum. They are cultivated at the Sudan Belt in the Savanna environment. On the other hand the representative crop from Roots is Yam. Maize has the range in every areas.
The crop rotation system is found in Northern Nigeria where Pearl Millet and Sorghum are taken as staple subsistence crop. In Middle and Southern Nigeria Yam is the first year's crop in its rotation system. In Southern Nigeria there is one or two years of cultivated period and the planted crops are almost Roots. In some areas the planting percentage of Maize amounts 20-30%. In the Intermediate area between the North and the South, the rotation system is generally practised: in the first year they plant Yam, then after Cereals and Roots by rotation. In such a process we are able to recognize the transitive phases from the crop rotation system toward the millet cultivation type or the root cultivation type which Sasaki had suggested. This root cultivation type also coincides with the wood fallow as the fallow system.
In comparing with each land use patterns at the unit of village, it has been made out that this pattern distinctly reflects the crop rotation system.