effect of long-term cattle grazing on root distribution and morphological characteristics of brachiaria decumbens (case study: tropical pasture, malaysia)

root morphological and distribution responses of signal grass (brachiaria decumbens) to long-term cattle grazing were examined in a tropical pasture in malaysia. the treatments were no grazing by cattle and grazing at a moderate stocking density (2.7 animal unit/ha) under rotational grazing for 33 years. the method consists of taking soil core using a soil corer to a depth of 30 cm and extracting roots from cores by hand-washing and subsequent measuring of root morphological characteristics including length, surface area, average diameter and volume using winrhizo root scanner. root length density, mass density, surface area density, and volume density were calculated as indicators of root distribution pattern in the soil volume. data were analyzed using repeated measure analysis of variance and independent t-test. root diameter, length and length density were affected neither by grazing treatment nor the interaction between them (p > 0.05). root diameters in the middle (10–20 cm) and lower (20–30 cm) soil layers of grazed site were 50% and 72% greater than that in the ungrazed site. root volume, surface area and their densities were not affected (p > 0.05) by grazing and the interaction between grazing and soil depth. mean root mass and mass density were affected (p < 0.05) by moderate grazing and soil depth, and the interaction between them. mean root mass in all soil depths in grazed site was greater than that in the ungrazed site. long-term rotational moderate grazing has no negative impact on root variables of signal grass in tropical pasture.