PHD-School of Humanities & Social Sciences

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This collections contains bibliographic information and abstracts of PHD theses and dissertation in the School of Humanities & Social Sciences held in Kenyatta University Library

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Browsing PHD-School of Humanities & Social Sciences by Subject "Acacia Auriculiformis"

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    Productivity and Cost-Benefit Assessment of Agroforestry Systems Based on Pentaclethra Macrophylla and Acacia Auriculiformis in Lobilo Catchment, Democratic Republic of Congo.
    (Kenyatta University, 2023-11) Assani, Neville Mapenzi; Raphael Kweyu; Nsharwasi Léon. Nabahungu
    Agroforestry systems (AFS) have a good reputation for boosting soil fertility and crop production and providing ecological services, all of which are necessary to ensure continued food security for a rising population without severely worsening environmental conditions. Pentaclethra macrophylla and Acacia auriculiformis are among important tree species used in AFS in Congo basin. Positive or negative effects of these trees on crop production, carbon (C) storage and financial profit in agroforestry system have been poorly or not been addressed in earlier studies. Hence, this research compares the impact of Pentaclethra macrophylla (native species) and Acacia auriculiformis (exotic species) based AFS on soil macro-nutrients, food crops (cassava, maize, and peanut crops) yield, the above ground and soil organic carbon as well as the financial profit during two cultural years. The study sought to investigate the effect of these trees and their planting densities on AFS productivity and financial income. The plot experimentation was a multifactor design implemented through Lobilo catchment in Democratic Republic of Congo (DRC). This experiment had 2 tree-species, 4 tree- planting density or tree-spacings (2500, 625 and 278 trees×ha-1 as well as monocropping), and 3 food crops. Noted that each pot has been replicated 3 times. Thus, this multifactorial trial had a total of 72 plots (2 trees species × 3 food crops × 4 planting densities × 3 repetitions) and each plot size was 400 m2, 3.2 ha at total. It was implemented between March 2020 and March 2022 corresponding to four cropping seasons. All analyses and visualization were performed using R 4.2.1 version (R Core Team 2022). Mixed effect regression analysis was carried out to assess the link between studied parameters and treatments and analysis of variance (ANOVA) was used to estimate marginal means computed for the significant sources of variation and treatments comparisons adjusted to identity homogeneous groups. The results revealed that the two agroforestry-species did not differ significantly with regard to their effects on soil nutrients, however, the total N, P and the pH increased over the growing of cropping season. Concerning the food crops yield variation, the yields of cassava and maize were greater under P. macrophylla than under A.auriculiformis. Furthermore, the tree density of 2500 trees×ha-1 of the both tree species negatively affect food crops yield. Concerning the Carbon storage, A.auriculiformis stocks more AGC than P. macrophylla. Likewise, concerning the financial profit of these AFS, the high planting density (2500 trees per hectare) decreases the financial profit because the most cost for the implementation of this AFS is spend for seedlings production. Furthermore, the both tree legume species associated with cassava shows positive net revenue but when associated with maize and peanut they show negative net revenue. This study has increased our knowledge on the association of P.macrophylla (native trees) and A.auriculiformis (exotic trees) with food crops by suggesting that the both tree species can be used in agroforestry systems at 625 trees×ha-1 associated with Cassava for financial profit and associated with peanut for biomass and above ground carbon benefit. Moreover P.macrophylla is more efficient in food crops production while A.auriculiformis is more efficient in above ground carbon storage. Therefore, there is need to enact laws that extend the association of native trees species with food crop in agroforestry system for balancing the needs of biodiversity preservation, food security, and ecosystem services in Democratic Republic of Congo. This research encourages scaling out this AFS system using other native tree species in Congo basin in order to meet food security without significantly degrade the environment.