CONVERSÃO DO CERRADO EM PASTAGENS CULTIVADAS E FUNCIONAMENTO DE LATOSSOLOS

Resumo

No desenvolvimento do projeto IRD-Embrapa, foi estudado o funcionamento de Latossolos segundo abordagens físicas, hidrodinâmicas, biológicas e de geoquímica do fósforo, na conversão da vegetação nativa em pastagens cultivadas com Brachiaria spp. Este trabalho apresenta uma síntese das transformações ocorridas nos solos sob pastagens, os processos de transformação da vegetação e os aspectos práticos relacionados a essa importante área de pastagens cultivadas do Cerrado brasileiro.

Termos para indexação: recursos naturais e meio ambiente, pecuária, solos.

THE CERRADO BIOMA CONVERSION
TO CULTIVATED PASTURES AND FERRALSOLS FUNCTIONING
ABSTRACT

During an IRD-Embrapa project the functioning of ferralsols has been studied with regard to its physics, hydrodynamics and biology and the geochemistry of phosphorus against a background of the transformation of the natural savannah vegetation into cultivated Bracharia spp. pastures. This paper describes the main balances and attempts to clarify the features of the soils under pasture which are affected, and in particular ferralsols. The work has shown that the state of the soil under an old, unproductive pasture is characterised by medium-low organic matter content and very low concentrations of plant-available phosphate ions. The surface horizon usually exhibits a loss of porosity and the soil structure is altered, being more compacted. The hydraulic properties do not seem to be greatly affected, and runoff and erosion are only localised problems resulting from very bad soil management practices used on certain watershed catchment bassin. The diversity and biomass of the soil macrofauna are reduced. However the physical and biogeochemical behaviour recorded indicate that properties favourable to plant growth can be restored by changing the management of the system. On the other hand, we have shown that these soils remain very susceptible to fluctuating rainfall, the available water reserve declining rapidly, particularly when the fine porosity falls. But the cause of the decline in this case is the occurrence of short dry seasons.

Index terms: natural resources and environment, pastures, soil.

CONVERSION DU CERRADO EN PÂTURAGES CULTIVÉS
ET FONCTIONNEMENT DES FERRALSOLS
RÉSUMÉ

Dans le cadre d'un projet de recherche Institut de recherche pour le développement-Empresa brasileira de pesquisa agropecuária (IRD-Embrapa) le fonctionnement des Ferralsols a été abordé, sous l'angle des propriétés physiques, hydrodynamiques, biologiques et géochimiques du phosphore, lors de la transformation de la savane en pâturages cultivés à base de Brachiaria spp. Cette contribution en dresse les principaux bilans et apporte des éclairages sur l'évolution des sols sous pâturages, les processus concernés par le changement de végétation et des aspects pratiques qui concernent les vastes étendues de pâturages cultivés du Cerrado.

Termes d'indexation: ressources naturelles et environnement, productions végétales, sols.