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Accueil du site → Doctorat → Afrique du Sud → 2022 → The role of nutritional status of soils from grassland and savanna ecosystems on the biochemical and physiological responses of Vigna unguiculata L. (Walp)

University of KwaZulu-Natal (2022)

The role of nutritional status of soils from grassland and savanna ecosystems on the biochemical and physiological responses of Vigna unguiculata L. (Walp)

Makaure, Brenda Tsungai.

Titre : The role of nutritional status of soils from grassland and savanna ecosystems on the biochemical and physiological responses of Vigna unguiculata L. (Walp)

Auteur : Makaure, Brenda Tsungai.

Université de soutenance : University of KwaZulu-Natal

Grade : Doctor of Philosophy in the Discipline of Biological Sciences, 2022

Résumé partiel
Most arable soils in sub–Saharan Africa savanna and grassland ecosystems are acidic and nutrient deficient with nitrogen and phosphorus being the most limiting and this poses a huge threat to agricultural productivity. To overcome soil nutrient deficiency and increase crop yields, farmers have resorted to high inputs of synthetic fertilizers, which are expensive and may cause environmental degradation. Use of legumes is an important alternative as they help enhance soil nutrition through biological nitrogen fixation. Vigna unguiculata L. (Walp), a highly nutritious legume crop that could be incorporated in small scale cropping systems to improve soil nutrition. However, there is limited information on the physiological and biochemical strategies enabling the growth of V. unguiculata under acidic and nutrient stress conditions. In this study it was hypothesized that symbiotic association between V. unguiculata and rhizospheric microbes affects the growth, nutrient assimilation and phytochemicals of the grain legume grown in nutrient stressed soils. Firstly, this study evaluated the physicochemical properties, microbial composition and soil enzymes activities of soils from four geographically distinct regions of KwaZulu-Natal representing savanna and grassland ecosystems. Secondly, the study investigated how the tripartite symbiosis of V. unguiculata, arbuscular mycorrhizal fungi and nodulating bacteria affect phosphorus and nitrogen nutrition, and the growth of V. unguiculata grown under acidic and nutrient stress conditions. Then, the study investigated how four V. unguiculata varieties regulated their phenolic acids and antioxidants to enhance their growth in acidic and nutrient stressed soils conditions. The four soil types were acidic with low mineral nutrients, with Bergville being the most acidic. The soils were significantly different in their physicochemical and microbial composition. Most bacterial strains identified in the soils belonged to genera Lysinibacillus, and Bacillus while the most identified fungal strains belonged to Fusarium and Trichoderma genera. There were variations in soil lignin degrading, C, N and P cycling enzyme activities.

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