INFLUENCE OF DIFFERENT GRAZING SYSTEMS ON PHYSICAL PROPERTIES AND AGGREGATION IN SAVANNAH SOILS

Abstract

The objective of this study was to evaluate soil structure alterations that occurred in a typical Red distroferric Latossol under different grazing systems. In 2004, soil samples from three depths (0-2 cm, 2-7 cm, and 30-35 cm) were collected in a farm owned by the College of Veterinary of the Federal University of Goiás, Goiânia, Goiás State, Brazil, as it follows: I) soil under pasture with Panicum maximum cv. Tanzania, in a rotational grazing system, clump position (“C”); II) soil under pasture with Panicum maximum cv. Tanzania, in a rotational grazing system, among clumps position (“AC”); III) soil under pasture with Cynodon dactilum cv. Tifton 85, in a continuous grazing system; and IV) soil under Savannah, as reference. The implantation of pastures with Tifton 85 and Tanzania grasses changed physical properties of the soil, through the reduction of macropores (MAC) and increase in soil density (SD). Soils under pastures with Tifton 85 and Tanzania grasses (“C” position) presented larger mean geometric diameter (MGD), if compared to the soils under Savannah and pasture with Tanzania grass (“AC” position). Alterations in soil structure were more significant in the topsoil layer (0-2 cm and 2-7 cm depth). Stocking rates practiced in the pastures with Tifton 85 and Tanzania grasses were excessive and also the main reason for deteriorating physical soil properties.

KEY-WORDS: Cynodon dactilum; Panicum maximum; continuous grazing system; rotational grazing system; stocking rate.