||SLASH AND BURN
Definition characters description and diffusion
The practice known as slash and burn or shifting cultivation is one of the traditional cropping systems. In early times, clearing of the bushland with hand axes and hoes was limited to removing branches of trees, leaving tree stumps to re-grow (coppice). The surrounding field was cleared of grass, most of the organic material burnt and the residual material including ashes spread over the field.
General characters description and diffusion
Local variations were developed to suit different conditions. The cleared area varied from small patches, such as a circle around prominent trees (the Chitemene system practiced in central Africa) to open patches in the woodlands. Shifting cultivation was also practiced in non-wooded areas along the desert margins, when the cultivated field became degraded due to loss of nutrients or salinization. Slash and burn agriculture was efficient and sustainable when human and livestock populations were low. Burning leaves a clean seedbed in which crops are planted directly without disturbing the soil. The ash fertilizes the soil and the heating destroys weeds and soil-borne pests and diseases. The garden, also known as swidden fields, was cultivated for one to three years. In the past, the land could be given up to 20-30 years to recover, hence assuring sustinability. Slash and burn practice allowed the survival of human communitites in perfect harmony with resources over a very long time. But, it can be disastrous if applied in a completely different environmental and demographic context. Today, with increased numbers of people and livestock, adequate fallow periods are not possible and the trees do not have enough time to regenerate. Slash and burn agriculture is still practiced in developing countries but the fallow period has been shortened to eight years or less in the Sudan and elsewhere and the large circles have shrunk with declining tree resources. In the less industrialized countries, the main cause of the dissappearance of traditional techniques is poverty. It is poverty created by the sudden development of new needs and models whicxh have impoverished local resources. For instance, cooking practiced with traditional fuels is indicated as the only cause of the deforestation of the plant cover in many regions of the Sahel. However, traditionally, in a situation of non-poverty, fuels made from animal dung were used, or only the dry parts and branches of trees were cut in order to respect and protect them in the name of sacred symbolism. These practices were abondonded only in situations of economic shortage, the decline of cultural values with massive urbanization and the dissappearance of the integrated cycle of cultivation and breeding.
Advantages and sustainability
No longer sustainable, slash and burn used to offer benefits to communities by burning organic material in areas of heavy agricultural activity, introducing burnt organic material into the soils which fertilizes them simultaneously killing diseases or pests, and leaves the soil clean for new crops.