Slash and burn agriculture

Rumpel, C., Alexis, M., Chabbi, A., Chaplot, V., Rasse, D. P., Valentin, C., and Mariotti, A. (2006). Black carbon contribution to soil organic matter composition in tropical sloping land under slash and burn agriculture. Geoderma 130, 35-46. 

Forest based farmers practice slash-and-burn agriculture, clearing a new field from the forest, cropping it for 2-5 years and then leaving it fallow for 5-20 years. Fallow periods decrease due to growing population density. Forest products and game animals are the main source of cash income. Physical isolation and lack of roads and markets obstruct development. 

The Amazonian rain forest planet earth s foremost ecological disaster area, where thousands of acres and entire species are sacrificed forever on an around-the-clock basis to short-term slash-and-burn agriculture a two million square mile monument to human arrogance and stupidity. Most of us nave never seen it, most of us never will. From this the user. Users also seem to see the experience as real, not a "hallucination" in the usual sense of the word, and a portal to other worlds which exist alongside our own. ... 

The World Conservation Union reports that 34,000 plant species out of 270,000 are threatened.426 This includes one-third of all lily, palm, and Dipterocarpacae species. Forests once covered 40% of the land on earth. This has now been reduced by one-third.427 Tropical forests have been reduced by 50% in the last 50 years, half of this being due to slash and burn agriculture.428 More than 2000 species of birds (about 15% of the world s total)... 

Ramakrishnan, P.S., and O. P. Toky. 1981. Soil nutrient status of hUl-agroecosystems and recovery after slash and burn agriculture (Jhum) in north-eastern India. Plant and Soil 60 41-64. 

Perhaps one of the earliest and most influential studies that compared the agricultural impact of manual (slash-and-burn) and mechanical (bulldozer) clearing for pasture establishment in the Amazon basin was that of Seubert et al. (1977) in Peru. In that study, pasture (Panicum maximum) biomass produaion, over a 2-year period, was 68 % higher in the area cleared manually. Other studies have followed, with the general conclusion that pastures manually cleared from forest were more productive and that mechanical clearing adversely affected soil physical and chemical properties (e.g., Alegre 1985, Toledo and Morales 1979, Dias and Northcliff 1985). 

Ketterings, Q.M., van Noordwijk, M. and Bigham, J.M. (2002) Soil phosphorus availability after slash-and-burn fires of different intensities in rubber agroforests in Sumatra, Indonesia. Agriculture, Ecosystems and Environment 92, 37 8. 

Combustion in incinerators, or by open burning, may lead to the production of low molecular weight oligomers, or of chlorinated C1-C2 materials such as methyl chloride. Methyl chloride has been postulated as a major product of the combustion of agricultural waste, and of slash and burn land clearance [42] estimates suggest that as much as 5 x 10 tonnes per year of methyl chloride could be emitted from all fires throughout the world. There have been suggestions that both chloroform and carbon tetrachloride may have a natural atmospheric source, by chlorination of methane [34] but there is no confirmation, despite their ubiquitous presence, and the known occurrence of free chlorine. 

---