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8 results on '"KwaZulu-Natal Department of Agriculture and Environmental Affairs"'

1. Surface organic carbon enrichment to explain greater CO2 emissions from short-term no-tilled soils

Author

Colin S. Everson, Khatab Abdalla, Hocine Bourennane, H. Thenga, Marie Alexis, Daniel Müller-Nedebock, Macdex Mutema, Phesheya Dlamini, Pauline Chivenge, Katell Quénéa, Charmaine Mchunu, Frédéric Darboux, Vincent Chaplot, School of Agricultural, Earth & Environmental Sciences, Centre for Water Resources Research (CWRR), University of KwaZulu-Natal (UKZN), Biogéochimie-Traceurs-Paléoclimat (BTP), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN), Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE)-Centre National de la Recherche Scientifique (CNRS), Unité de recherche Science du Sol (USS), Institut National de la Recherche Agronomique (INRA), Soil Fertility and Analytical Services, KwaZulu-Natal Department of Agriculture and Environmental Affairs, Matopos Research Station, International Crop Research Institute for the Semi-Arid Tropics (ICRISAT), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC), University of KwaZulu-Natal [Durban, Afrique du Sud] (UKZN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Unité de Science du Sol (Orléans) (URSols), and Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE)

Subjects
Crop residue, non travail du sol, maïs, No-tillage, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Context (language use), Sciences de la Terre, dioxyde de carbone, non labour, Climate change, propriété du sol, 2. Zero hunger, Topsoil, changement climatique, Conventional tillage, Ecology, Soil organic matter, 15. Life on land, Carbon dioxide, Maize, Small holders, Africa, Tillage, Agronomy, 13. Climate action, émission d'azote, Soil water, Earth Sciences, Environmental science, Soil horizon, Animal Science and Zoology, afrique du sud, Agronomy and Crop Science, azote du sol
Abstract

The impact of agricultural practices on CO2 emissions from soils needs to be understood and quantified to enhance ecosystem functions, especially the ability of soils to sequester atmospheric carbon (C), while enhancing food and biomass production. The objective of this study was to assess CO2 emissions in the soil surface following tillage abandonment and to investigate some of the underlying soil physical, chemical and biological controls. Maize (Zea mays) was planted under conventional tillage (T) and no-tillage (NT), both without crop residues under smallholder farming conditions in Potshini, South Africa. Intact top-soil (0–0.05 m) core samples (N = 54) from three 5 × 15 m2 plots per treatment were collected two years after conversion of T to NT to evaluate the short-term CO2 emissions. Depending on the treatment, cores were left intact, compacted by 5 and 10 or had surface crusts removed. They were incubated for 20 days with measurements of CO2 fluxes twice a day during the first three days and once a day thereafter. Soil organic C (SOC) content, soil bulk density (ρb), aggregate stability, soil organic matter quality, and microbial biomass and its activity were evaluated at the onset of the incubation. CO2 emissions were 22% lower under NT compared with T with CO2 emissions of 0.9 ± 0.10 vs 1.1 ± 0.10 mg C–CO2 gC−1 day−1 under NT and T, respectively, suggesting greater SOC protection under NT. However, there were greater total CO2 emissions per unit of surface by 9% under NT compared to T (1.15 ± 0.03 vs 1.05 ± 0.04 g C–CO2 m−2 day−1). SOC protection significantly increased with the increase in soil bulk density (r = 0.89) and aggregate stability (from 1.7 ± 0.25 mm to 2.3 ± 0.31, r = 0.50), and to the decrease in microbial biomass and its activity (r = −0.59 and −0.57, respectively). In contrast, the greater NT CO2 emissions per m2 were explained by top-soil enrichment in SOC by 48% (from 12.4 ± 0.2 to 19.1 ± 0.4 g kg−1, r = 0.59). These results on the soil controls of tillage impact on CO2 emissions are expected to inform on the required shifts in agricultural practices for enhancing C sequestration in soils. In the context of the study, any mechanism favoring aggregate stability and promoting SOC allocation deep in the soil profile rather than in the top-soil would greatly diminish soil CO2 outputs and thus stimulate C sequestration.

Published
2015
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2. Impact de la dégradation des terres sur la génération du ruissellement. Résultats clefs du bassin Thukela (Afrique du Sud)

Author

Chaplot, Vincent, Abdalla, Khatab, Alexis, Marie, Chivenge, Pauline, Darboux, Frédéric, Dlamini, Phesheya, Everson, Colin, Jewitt, Graham P. W., Lorentz, Simon, Mchunu, Charmaine, Muller-Nedebock, D., Mutema, Macdex, Oakes, Ernest, Orchard, C., Quenea, Katell, Thenga, H., Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), School of Agricultural, Earth & Environmental Sciences, Centre for Water Resources Research (CWRR), University of KwaZulu-Natal [Durban, Afrique du Sud] (UKZN), Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Matopos Research Station, International Crop Research Institute for the Semi-Arid Tropics (ICRISAT), Unité de recherche Science du Sol (USS), Institut National de la Recherche Agronomique (INRA), Soil Fertility and Analytical Services, KwaZulu-Natal Department of Agriculture and Environmental Affairs, Institute for Hydraulic Engineering and Water Resources Management., Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), University of KwaZulu-Natal (UKZN), Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC), and ProdInra, Migration

Subjects
[SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2014

3. Land degradation impact on soil organic carbon and nitrogen stocks of sub-tropical humid grasslands in South Africa

Author

Phesheya Dlamini, Alan Manson, Vincent Chaplot, Pauline Chivenge, School of Agricultural, Earth & Environmental Sciences, Centre for Water Resources Research (CWRR), University of KwaZulu-Natal (UKZN), Kwazulu-Natal Department of Agriculture and Environmental Affairs, Biogéochimie-Traceurs-Paléoclimat (BTP), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), University of KwaZulu-Natal [Durban, Afrique du Sud] (UKZN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636))

Subjects
Land management, Soil Science, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Ecosystems, Grassland, Pasture, Climate change, Organic matter, ComputingMilieux_MISCELLANEOUS, 2. Zero hunger, chemistry.chemical_classification, geography, geography.geographical_feature_category, Ecology, Carbon cycle, Soil carbon, 15. Life on land, Agronomy, chemistry, 13. Climate action, Loam, Soil water, Land degradation, Environmental science, Rangeland
Abstract

Land degradation is recognized as a main environmental problem that adversely depletes soil organic carbon (SOC) and nitrogen (SON) stocks, which in turn directly affects soils, their fertility, productivity and overall quality. While it is expanding worldwide at rapid pace, quantitative information on the impact of land degradation on the depletion of SOC and SON stocks remains largely unavailable, limiting the ability to predict the impacts of land management on the C losses to the atmosphere and associated global warming. The main objective of this study was to evaluate the consequences of a decrease in grass aerial cover on SOC and SON stocks. A degraded grassland showing an aerial cover gradient from 100% (Cov100, corresponding to a non-degraded grassland) to 50-75% (Cov75), 25-50% (Cov50) and 0-5% (Cov5, corresponding to a heavily degraded grassland), was selected in South Africa. Soil samples were collected in the 0.05 m soil layer at 48 locations along the aerial cover gradient and were subsequently separated into the clay + silt (2-20 mu m) and sand (20-2000 mu m) fractions, prior to total C and N analysis (n = 288). The decline in grass aerial cover from 100% to 0-5% had a significant (P < 0.05) impact on SOC and SON stocks, with losses by as much as 1.25 kg m(-2) for SOC and 0.074 kg m(-2) for SON, which corresponded to depletion rates of 89 and 76%, respectively. Furthermore, both the C:N ratio and the proportion of SOC and SON in the silt + clay fraction declined with grass aerial cover, which was indicative of a preferential loss of not easily decomposable organic matter. The staggering decline in SOC and SON stocks raises concerns about the ability of these acidic sandy loam soils to sustain their main ecosystem functions. The associated decrease in chemical elements (e.g., Ca by a maximum of 67%; Mn, 77%; Cu, 66%; and Zn, 82%) was finally used to discuss the mechanisms at stake in land degradation and the associated stock depletion of SOC and SON stocks, a prerequisite to land rehabilitation and stock replenishment.

Published
2014
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4. A Bayesian approach for inferring the dynamics of partially observed endemic infectious diseases from space-time-genetic data

Author

Sunny E. Townsend, Katie Hampson, Louis Hendrik Nel, Daniel T. Haydon, Kevin Le Roux, Nardus Mollentze, Samuel Soubeyrand, Department of Microbiology and Plant Pathology, University of Pretoria [South Africa], Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, KwaZulu-Natal Department of Agriculture and Environmental Affairs, Biostatistique et Processus Spatiaux (BioSP), Institut National de la Recherche Agronomique (INRA), NRF [74606], PRF [11/85], University of Pretoria Postgraduate Study Abroad Programme, Wellcome Trust [095787/Z/11/Z], UK Medical Research Council (MRC) [G0901135], ANR (grant EMILE), and MRC [G0901135]

Subjects
0106 biological sciences, Rabies, Bayesian probability, Population, Molecular Sequence Data, Biology, 010603 evolutionary biology, 01 natural sciences, Communicable Diseases, Models, Biological, General Biochemistry, Genetics and Molecular Biology, Time, 03 medical and health sciences, Bayes' theorem, South Africa, Dogs, Disease Transmission, Infectious, Animals, rabies virus, [INFO]Computer Science [cs], [MATH]Mathematics [math], Rabies transmission, education, Spatial analysis, Research Articles, endemic disease, 030304 developmental biology, General Environmental Science, 0303 health sciences, education.field_of_study, General Immunology and Microbiology, Base Sequence, Spatial epidemiology, Bayes Theorem, General Medicine, Virology, 3. Good health, Infectious disease (medical specialty), Evolutionary biology, Communicable disease transmission, spatial epidemiology, surveillance, General Agricultural and Biological Sciences, Epidemiologic Methods, transmission trees
Abstract

International audience; We describe a statistical framework for reconstructing the sequence of transmission events between observed cases of an endemic infectious disease using genetic, temporal and spatial information. Previous approaches to reconstructing transmission trees have assumed all infections in the study area originated from a single introduction and that a large fraction of cases were observed. There are as yet no approaches appropriate for endemic situations in which a disease is already well established in a host population and in which there may be multiple origins of infection, or that can enumerate unobserved infections missing from the sample. Our proposed framework addresses these shortcomings, enabling reconstruction of partially observed transmission trees and estimating the number of cases missing from the sample. Analyses of simulated datasets show the method to be accurate in identifying direct transmissions, while introductions and transmissions via one or more unsampled intermediate cases could be identified at high to moderate levels of case detection. When applied to partial genome sequences of rabies virus sampled from an endemic region of South Africa, our method reveals several distinct transmission cycles with little contact between them, and direct transmission over long distances suggesting significant anthropogenic influence in the movement of infected dogs.

Published
2014
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5. Rainfall simulation to identify the storm-scale mechanisms of gully bank retreat

Author

Jean-Louis Janeau, Cornelia Rumpel, Pascal Podwojewski, Jacqueline Brown, Lauren Martin, Vincent Chaplot, Charmaine Nontokozo-Mchunu, Phesheya Dlamini, Ernest Oakes, Graham Jewitt, Simon Lorentz, Nhlakanipho Zondi, Sylvain Revil, Tarryn Eustice, Institut de Recherche pour le Développement (IRD [Réunion]), University of KwaZulu-Natal (UKZN), University of Pretoria [South Africa], South African Sugarcane Research Institute, KwaZulu-Natal Department of Agriculture and Environmental Affairs, Biogéochimie et écologie des milieux continentaux (Bioemco), Centre National de la Recherche Scientifique (CNRS)-AgroParisTech-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Netherlands Foundation for the Advancement of Tropical Research (WOTRO), Swedish International Development Cooperation Agency (Sida), Netherlands Directorate-General of Development Cooperation (DGIS), International Water Management Institute (IWMI), UNESCO-IHE Institute for Water Education, Departement Soutien Formation (DSF) of the Institut de Recherche pour le Developpement (IRD, former ORSTOM), School of Bioresources Engineering and Environmental Hydrology, Rabie Saunders Building, University of Kwazulu-Natal, University of KwaZulu-Natal [Durban, Afrique du Sud] (UKZN), École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS)

Subjects
Bank retreat, Watershed, 010504 meteorology & atmospheric sciences, Erosion control, [SDV]Life Sciences [q-bio], Soil Science, INTERRILL EROSION, 01 natural sciences, CHINA, South Africa, NORTHERN LAOS, Gully erosion, SLOPING LANDS, ERODIBILITY, RATES, Bank erosion, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Hydrology, Splash, Involved mechanisms, Storm, 04 agricultural and veterinary sciences, 15. Life on land, SOUTH-AFRICA, Bulk density, SOIL, MODEL, [SDE]Environmental Sciences, 040103 agronomy & agriculture, Erosion, 0401 agriculture, forestry, and fisheries, Environmental science, Surface runoff, Agronomy and Crop Science
Abstract

International audience; Gully erosion is one of the main causes of soil loss in drylands. Understanding the dominant mechanisms of erosion is important to achieve effective erosion control, thus in this study our main objective was to quantify the mechanisms involved in gully bank retreat as a result of three processes, falling of entire soil aggregates, transport of soil material by splash and by water running along gully banks (runoff). during rainfall events. The study was conducted in the sloping lands of the KwaZulu-Natal province, a region that is highly affected by gully erosion. Artificial rain was applied at 60 mm h(-1) for 45 min at the vertical wall of a gully bank typical to the area. The splash material was collected by using a network of 0.045 m(2) buckets. The sediments in the running water were assessed by sampling the runoff collected from a microplot inserted within the base of the bank, and collecting the fallen aggregates after the rainfall simulation was complete. Results indicated that the overall erosion for the simulation was 721 g m(-2) h(-1). Runoff erosion proved to be the dominant mechanism and amounted to 450g m(-2) h(-1), followed by splash and fall down of aggregates (about 170 g m(-2) h(-1)). Gully bank retreat occurred at a rate of 0.55 mm h(-1) and assuming that the soil bulk density is 1.3 g cm(-3), this corresponds to a retreat of 8.8 mm y(-1). Extrapolations to the watershed level, where about 500 m(2) of gully bank are observed per hectare, would lead to an erosion rate of 4.8 t ha(-1) y(-1). These limited results based on a simulated storm show that the three main mechanisms (runoff, splash and fall down of aggregates) are responsible for the retreat of gully banks and that to mitigate gully erosion, appropriate measures are required to control all three mechanisms. Further research studies are needed to confirm and to scale up, both in time and space, as these data are obtained at one location and from a single artificial storm. (C) 2010 Elsevier B.V. All rights reserved.

Published
2011
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6. A Bayesian approach for inferring the dynamics of partially observed endemic infectious diseases from space-time-genetic data.

Author

Mollentze N, Nel LH, Townsend S, le Roux K, Hampson K, Haydon DT, and Soubeyrand S

Subjects
Animals, Base Sequence, Bayes Theorem, Communicable Diseases transmission, Communicable Diseases veterinary, Dogs, Models, Biological, Molecular Sequence Data, Rabies transmission, Rabies veterinary, Rabies virus genetics, South Africa, Time, Communicable Diseases epidemiology, Disease Transmission, Infectious statistics & numerical data, Epidemiologic Methods, Rabies epidemiology
Abstract

We describe a statistical framework for reconstructing the sequence of transmission events between observed cases of an endemic infectious disease using genetic, temporal and spatial information. Previous approaches to reconstructing transmission trees have assumed all infections in the study area originated from a single introduction and that a large fraction of cases were observed. There are as yet no approaches appropriate for endemic situations in which a disease is already well established in a host population and in which there may be multiple origins of infection, or that can enumerate unobserved infections missing from the sample. Our proposed framework addresses these shortcomings, enabling reconstruction of partially observed transmission trees and estimating the number of cases missing from the sample. Analyses of simulated datasets show the method to be accurate in identifying direct transmissions, while introductions and transmissions via one or more unsampled intermediate cases could be identified at high to moderate levels of case detection. When applied to partial genome sequences of rabies virus sampled from an endemic region of South Africa, our method reveals several distinct transmission cycles with little contact between them, and direct transmission over long distances suggesting significant anthropogenic influence in the movement of infected dogs.

Published
2014
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7. International Fungicide Efficacy Trials for the Management of Soybean Rust.

Author

Miles MR, Levy C, Morel W, Mueller T, Steinlage T, van Rij N, Frederick RD, and Hartman GL

Abstract

The efficacy of fungicides in managing soybean rust was evaluated in 12 environments in South America and southern Africa over three growing seasons from 2002 to 2005. There were differences in final soybean rust severity, defoliation, and yield among the treatments at most locations. In locations where soybean rust was not severe, all the fungicides evaluated reduced severity. In locations where soybean rust was severe, applications of triazole and triazole + strobilurin fungicides resulted in lower severity and higher yields compared with other fungicides. The strobilurin fungicides provided the highest yields in many locations; however, severity tended to be higher than that of the triazole fungicides. There also were differences in yield and severity between the trials with two and three applications of several fungicides, with three applications resulting in less severe soybean rust and higher yields. However, the third application of tebuconazole, tetraconazole, and the mixtures containing azoxystrobin and pyraclostrobin was not needed to maintain yield. These fungicides were among the most effective for managing soybean rust and maintaining yield over most locations.

Published
2007
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8. First Report of Soybean Rust Caused by Phakopsora pachyrhizi on Dry Beans in South Africa.

Author

du Preez ED, van Rij NC, Lawrance KF, Miles MR, and Frederick RD

Abstract

During April 2004, a 150-m 2 dry bean (Phaseolus vulgaris) plot growing adjacent to rust-infected soybean (Glycine max) at Cedara Agricultural Research Farm (29°32'S 30°16'E) was observed to be infected with two distinct rust types. Common bean rust (caused by Uromyces appendiculatus) with reddish brown uredinia and black telia was readily identified. A second rust with smaller sporulating uredinia (1.0 to 1.5 mm 2 ), which were gray in appearance, was also found. Visual rust severity on the dry bean plants, which were in mid pod-fill, was high (approximately 30 to 40% disease incidence). Twenty plants were examined and observed to be infected with both rusts. With microscopic examination of no fewer than 20 leaves per plant, the urediniospores from the smaller lesions were determined to be morphologically similar to Phakopsora pachyrhizi (3). Real-time fluorescent polymerase chain reaction assays on six leaves and sequence analysis of the nuclear ribosomal internal transcribed spacer region 2 (1) verified the identity of the urediniospores as P. pachyrhizi. Although P. vulgaris is a known host of P. pachyrhizi, to our knowledge this is the first time since the arrival of soybean rust in 2001 that P. pachyrhizi has been observed on an alternate host plant in South Africa (2). Since dry beans are grown all year in frost-free areas, the implications are that dry beans may serve as an important overwintering host and source of inoculum for seasonal soybean rust outbreaks. References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) Z. A. Pretorius et al. Plant Dis. 85:1288, 2001. (3) J. B. Sinclair and G. L. Hartman. Soybean Rust. Pages 25-26 in: Compendium of Soybean Diseases, 4th ed. G. L. Hartman et al. eds. The American Phytopathological Society, St. Paul, MN, 1999.

Published
2005
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