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sur le développement des zones arides et semi-arides

Titre : Investigating the impact of cattle path erosion on soil organic carbon and nitrogen, Okhombe Valley, KwaZulu-Natal, Drakensberg, South Africa

Auteur : Blicq, Ashleigh Justine.

Université de soutenance : University of KwaZulu-Natal

Grade : Master of Science, in the School of Agricultural, Earth and Environmental Sciences 2018

Résumé partiel
While soil erosion is a natural geologic phenomenon, its exacerbation as a consequence of socioeconomic and political factors, threatens rural sustainability and livelihoods. Smallholder rural farmers within the KwaZulu-Natal Drakensberg region of South Africa are reliant on the surrounding grasslands for livestock grazing. Mismanagement of land through overgrazing, overstocking and livestock trampling have led to excessive cattle path formation and resultant soil erosion, which negatively affects these montane grasslands. Community members have identified cattle path formation, as a grave concern, as the loss of land through increase erosion leads to gully formation and presents a safety hazard to residents and livestock. This study investigated the impact of cattle path erosion on soil properties, in particular soil organic carbon (SOC) and nitrogen (N) along a degraded slope profile. For this purpose four positions (reference site, top-slope, mid-slope and lower-slope) were identified and sampled at three soil depths (0-5 cm, 5-15 cm and 15-30 cm) along a degraded slope at Okhombe, Drakensberg region South Africa. Soil properties, soil nutrients, SOC and N were measured (over a two day period) and physical soil fractionation were completed to determine carbon (C) and N protection within soil aggregates. To understand SOC and N distribution, areas of erosion and deposition were determined by measuring fallout radionuclides caesium-137 (137Cs) and excess lead-210 (210Pbex). Soil property measurements revealed that the undisturbed reference site contained higher nutrient content and greater C and N protection within soil aggregates compared to the degraded slope profile. This suggests that nutrient loss has occurred on the degraded slope, possibly as a result of cattle path erosion.

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