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sur le développement des zones arides et semi-arides

Titre : Soil nutrient status in the different land use systems and soil profiles of Seronga, Botswana

Auteur : Gwatidzo, Cornelia

Université de soutenance : University of Botswana

Grade Master of Philosophy in Natural Resource Management 2014

Résumé partiel
The status of soil physico-chemical properties as governed by land use systems at local level is necessary for determining soil productivity and appropriate management options for sustainable land use. A study investigating soil nutrient status in the different land use systems and soil profiles of Seronga, Botswana was conducted. A total of 597 soil samples were collected at different soil profile depths (0-10, 10-20, 20-30 and 30-40cm) in three seasons (i.e., onset of rains, peak of the rains and dry season) between 2011 and 2012. Both descriptive and comparative analyses were conducted to identify potential agricultural sites and assessing the effects of cultivation on soil properties. Seronga soils contained high sand (>90%) and low clay (0.4% to 2.8%), with pH (CaCl2) being acidic (woodland) and close to neutral (cropped land, fallow land and grassland). The soils have low moisture content (<9%) and electrical conductivity (<1mS/cm). On average (0-40cm soil profile), the highest (0.78±0.10%) and lowest (0.32±0.03%) soil organic matter content was recorded in tall mopane woodland at the onset of rains and in the dry season, respectively. Soil organic matter content was highest in the soil surface (0-10cm) samples. However, isolated instances of soil organic matter migration to the lower horizons were observed. Soil total nitrogen (N) was very low (<0.03%) at the onset of rains and dry season, showing a decrease with depth. Total N increased at the peak of rains ; with highest in Ximenia woodland (0.39±0.03%), grassland (0.37±0.01%) and Dichrostachys woodland (0.36±0.01%). Total phosphorous (P) was below detectable limit (<0.0001g/kg) at the onset of rains and in the dry season in all the land use systems and soil profiles. At the peak of rains, total P was high in tall mopane woodland (0.08±0.06g/kg) and in grassland (0.07±0.02g/kg). Available P ranged from 22.16±1.09mg/kg in grassland at the peak of rains to 1.98±0.09mg/kg in Terminalia woodland during the dry season, decreasing with soil depth. Generally very low levels (<0.02%) of total sulphur (S) were recorded in all land use systems and soil profiles.

Présentation (UBRISA) -> https://ubrisa.ub.bw/handle/10311/1...

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