Effect of grazing intensity on the root system of pasture

Abstract

The effect on the Brachiaria humidicola root system of two grazing systems (continuous and rotational) and of two stoking rates (2.2 and 4.2 heads per hectare) was evaluated in "tabuleiro" soils of Southern Bahia. Soil samples were collected for depths of 0-5, 5-10, 10-20, 20-50, 50-80 e 80-100 cm. The continuous and rotational grazing did not present a significant difference of root density (mg.100 cm^-3) in all depths of soil. The stocking rates in both the grazing systems had similar results. However, the rotational grazing, 2.2 heads per hectare stocking rate, favored a greater rooting, especially below the 0-20 cm depth. For evaluating the stocking rates effects on the root systems under continuous grazing the number of roots (N^o of roots. 100 cm^-3) was determined and the root length (cm. 100 cm^-3) by diameter class was estimated. The predominant effect of stocking rate gave roots smaller than 0.5 mm. The stocking rate of 2.2 head per hectare showed a strong tendency forward greater root length and number of roots than the 4.2 stocking rate as far as the 20 cm depth.