ABSTRACT
Summary Natural upland savanna grasslands are represented mainly by well-drained savannas, with the cerrado type predominant, and by poorly drained savannas with the campo alto-type being the most common. The main limitations are low forageproduction potential and, especially, low forage quality. About 3 million ha of rain forest has been replaced by improved pastures of guineagrass (Panicum maximum, 80%), jaraguagrass (Hyparrhenia rufa, 10%), and Brachiaria spp. and other grasses (10%). During the first few years after establishment, pastures are productive. However, with time, a gradual decline of productivity occurs, especially in P. maximum pastures. About 0.5 million ha is already in advanced stages of degradation. Limiting factors include climate and plant and soil factors, besides man's influence. Research was conducted on 14 private ranches representing the most important improved- and native-pasture ecosystems of the Amazon region, with the objective of developing technology for (1) reclaiming sown pastures at varying degrees of degradation, (2) increasing the longevity of still-productive sown pastures in forest areas, and (3) increasing productivity of lowproducing native pastures. Similar trials at all sites include the following: (1) introduction and evaluation of commercial forage species; (2) evaluation of grass-legume mixtures; (3) forage fertilization; (4) pasture reclamation, improvement, and management (grazing trials); and (5) adaptation of new forage germ plasm. Results indicate that (1) maintenance of pasture productivity requires careful management of the soil-animal-plant system; (2) even though guineagrass has been planted on 2.5 million ha, other grasses can be more successful; (3) longevity of stillproductive guineagrass pastures can be increased considerably by using appropriate grazing-management systems in combination with strategic use of phosphorus fertilization and legume introduction; (4) reclamation of guineagrass pastures in advanced stages of degradation can be achieved successfully by phosphorus fertilization and by introduction of low-demand grasses such as Brachiaria humidicola in combination with legumes, such as Pueraria phaseoloides.
