Long-Term Impacts Of Grazing Intensity On Soil Carbon Sequestration And Selected Soil Properties In The Arid Eastern Cape, South Africa

AbstractBACKGROUND

Little is known about how basic soil properties respond to contrasting grazing intensities in the Karoo biome, South Africa. The aim of this study was to investigate impacts of long￢ﾀﾐterm (>75 years) grazing at 1.18 heads ha￢ﾈﾒ1 (heavy; CGH), 0.78 heads ha￢ﾈﾒ1 (light; CGL), and exclosure on selected soil properties. Soil samples were collected to a depth of 60 cm from the long￢ﾀﾐterm experimental site of Grootfontein Agricultural Development Institute, Eastern Cape. The samples were analyzed for C, N, bulk density and infiltration rate, among others.

Generally, heavy and light grazing reduced soil N storage by 27.5% and 22.6%, respectively, compared with the exclosure. Animal exclusion improved water infiltration rate and C stocks significantly (P < 0.05), which was 0.128, 0.097, and 0.093 Mg ha￢ﾈﾒ1 yr￢ﾈﾒ1 for exclosure, CGL and CGH, respectively. Soil penetration resistance was higher for grazing treatments in the top 3￢ﾀﾓ7 cm soil layer but for exclosure at the top 1 cm soil surface.

Although livestock exclusion has the potential to improve C sequestration, a sufficient resting period for 1￢ﾀﾓ2 years followed by three consecutive grazing years at light stocking rate would be ideal for sustainable livestock production in this arid region of South Africa. ￂﾩ 2015 Society of Chemical Industry