Abstract
A field experiment was established on a Typic Paleudult soil in Yurimaguas, Peru, to compare the effect of slashing and burning with bulldozer land clearing of a tropical evergreen forest on the changes in soil properties during the first ten months after clearing and the performance of several crops at various fertility levels. The traditional slashing and burning method produced more favourable change in oil properties and crop yields than bulldozing. Burning increased the supply of exchangeable bases and available soil phos-phorus severalfold, decreased aluminium saturation, and retarded the organic matter decomposition process by about six months. In sharp contrast, the bulldozed areas suffered from severe soil compaction, did not receive additional base remained high in aluminium saturation levels and had available P and K value below the critical levels. Yields of upland rice (Oryza saliva), cassava (Manihot esculenta), maize (Zea mays), soya beans (Glycine max), and Guinea grass (Panicum maximum) were consistently superior in the burned clearings. Yield of unfertilized crop on the bulldozed plots were only 37 per cent of that of the burned plots. Crops receiving N, P and K applications yielded about half as much as bulldozed areas than in burned ones. Crops receiving N, P and K and limed to pH 6·2 produced 78 per cent of the yields of the burned clearings. Considering that bulldozer clearing costs about four times more than slashing and burning, both agronomic and economic parameters suggest the use of the traditional method in the transition from shifting to continuous cultivation.
