Physical impact of grazing by sheep on soil parameters in the Nama Karoo subshrub/grass rangeland of South Africa |
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| Authors: | G van N du Toit HA Snyman PJ Malan |
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| Institution: | 1. Japan Society of Ningen Dock, Academic Committee, Japan;2. Department of Clinical Health Science, Tokai University School of Medicine, Japan;3. Mitsui Memorial Hospital, Japan;1. Department of Animal Science, Faculty of Agriculture, University of Jiroft, P.O. Box 364, Jiroft, Iran;2. Department of Animal Science, College of Agriculture, Razi University, Kermanshah, Iran;1. University Museum, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway;2. Norwegian Institute for Nature Research (NINA), Gaustadalléen 21, NO-0349 Oslo, Norway;3. The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK;4. Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway;5. Norwegian University of Life Science, Department of Ecology and Natural Resource Management, P.O. Box 5003, NO-1432 Aas, Norway;6. Department of Environmental Sciences, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway;7. Norwegian Polar Institute, Polarmiljøsenteret, NO-9296 Tromsø, Norway;8. Scottish Natural Heritage, Silvan House, 231 Corstorphine Road, Edinburgh EH12 7AT, UK;9. Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, NO-0316 Oslo, Norway;1. CSIRO Agriculture and Food, PO Box 1700, Canberra, ACT 2601, Australia;2. University of New England & Central West Farming Systems, PO Box 171, Condobolin, NSW 2877, Australia;3. FarmLink Research, PO Box 240, Junee, NSW 2663, Australia;4. Department of Primary Industries NSW, Condobolin Agricultural Research & Advisory Station, PO Box 300, Condobolin, NSW 2877, Australia;1. Montpellier SupAgro, Institut Agro, University of Montpellier – UMR ABSys – UMR SYSTEM (Montpellier SupAgro, INRAE, CIRAD, CIHEAM IAMM), Montpellier, France;2. INRAE – UMR ABSys – UMR SYSTEM (Montpellier SupAgro, INRAE, CIRAD, CIHEAM-IAMM), Montpellier, France;3. ISARA, Research Unit Agroecology and Environment, Lyon, France;4. INRAE – UMR INNOVATION (Montpellier SupAgro, INRAE, CIRAD, University of Montpellier), Montpellier, France;5. CIRAD – UMR ABSys – UMR SYSTEM (Montpellier SupAgro, INRAE, CIRAD, CIHEAM-IAMM), Montpellier, France |
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| Abstract: | The direct short-term impact of three rates of stocking (4, 8 and 16 small-stock units SSU] ha?1) was quantified in terms of soil characteristics of arid Nama Karoo vegetation (subshrub/grass). Mature Merino wethers grazed in the experimental plots throughout May in 1995 and 1996 (the plots were not subjected to grazing at any other time). Stocking rate proved inversely related to initial infiltration rate. Light trampling (4 SSU ha?1) loosened the topsoil sufficiently to increase the initial infiltration rate: infiltration capacity of soil in fields stocked at 4 SSU ha?1 and 16 SSU ha?1 was 17% higher and 14% lower respectively than that of soil of ungrazed rangeland over the two grazing periods. Increased soil compaction and greater bulk density due to higher stocking rates significant decreased the infiltration rate. Compared to ungrazed rangeland stocking rates of 4, 8 and 16 SSU ha?1 over the two grazing periods increased bulk density respectively by 2.73%, 6.67% and 8.945% and compaction by 10.90%, 16.78% and 20.90%. No grazing also increased bulk density and soil compaction and decreased infiltration rate. Light stocking (4 SSU ha?1) influenced all soil parameters most favourably. From a hydrologic point of view, grazing levels and rotation schemes need to be tailored for sustainable utilization of arid subshrub/grass vegetation by livestock. |
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