EFFECTS OF LAND-CLEARING METHOD AND SOIL-MANAGEMENT ON CROP PRODUCTION IN THE AMAZON

The success of intensive, continuous cropping of newly cleared land in the humid tropics is highly dependent upon the method of land clearing and subsequent soil management. The objective of this study was to evaluate the effect of different land-clearing regimes, including initial tillage after clearing and subsequent soil management, on crop performance on an Ultisol in the Amazon Basin of Peru. The study was conducted on a Yurimaguas soil (fine-loamy, siliceous, isohyperthermic Typic Paleudult) covered by a 20-year-old evergreen forest which was cleared at the start of the experiment. Land-clearing treatments included slash and burn, bulldozing with a straight blade, and bulldozing with a shear blade. Post-clearing tillage methods were chisel-plowing and disking. Post-clearing soil management practices (subplots) included: (1) flat-planted, no fertilizer or lime added; (2) flat-planted, fertilizer and lime incorporated; and (3) soil bedded at a 1.1-m spacing and fertilizer and lime applied, as in subplot 2. The cropping sequence was upland rice [Oryza sativa L.]-soybean [Glycine max (1.) Merr.]-corn [Zea mays L.]-rice-corn. In general, all crops showed a positive response to the post-clearing tillage practices of chiseling and disking. The post-clearing soil-management practice combining fertilization, liming, and bedding generally produced the highest yields of rice and corn. The greatest average relative grain-yields, in descending order, were produced by the following management systems: slash/burn/flat-plant/fertilizer/lime (94% average relative grain-yield)slash/burn/bedded/fertilizer/lime (90%)shear-blade/burn/disk/bedded/fertilizer/lime (88%)shear-blade/burn/disk/flat-plant/fertilizer/lime (86%). © 1990.