Asigbaase, Michael
(2019)
Contribution of organic cocoa agroforestry to sustainable land management.
PhD thesis, University of Nottingham.
Abstract
This research was undertaken to evaluate the potential of organic and conventional cocoa agroforestry systems in different productive stages (Young, ≤ 15 years; Mature, 16 to 30 years; Old, ≥ 31 years) to contribute to sustainable land management through tree biodiversity conservation, carbon sequestration and nutrient recycling. It also assessed the influence of organic and conventional management of cocoa agroforestry systems on soil physico-chemical properties, cocoa pod production and crop (Musa spp.) yield. The study was conducted in the Moist Semi-deciduous Forest Zone of the Eastern Region of Ghana. Cocoa systems under organic management consistently maintained greater shade tree species diversity compared to those under conventional management. Shade tree species richness was higher on organic farms (5.10 ± 0.38) than conventional farms (3.48 ± 0.39). On organic farms, density of food and fruits shade trees (per ha) was three-fold (Org. 341 ± 38 vs. Con. 106 ± 18) when compared to conventional farms. Organically managed cocoa agroforestry systems demonstrated a greater potential to sequester and store carbon in the aboveground (39.6 Mg C ha-1), belowground (10.3 Mg C ha-1) and soil (0-30 cm depth, 59.7 Mg C ha-1) pools compared to conventionally managed cocoa systems (22.1 Mg C ha-1, 7.1 Mg C ha-1, 49.7 Mg C ha-1, respectively). The rate of total carbon storage (vegetation plus soils) ranged from 3.4 Mg C ha-1 yr-1 (young cocoa systems) to 9.0 Mg C ha-1 yr-1 (old cocoa systems) in the organic systems and 1.1 Mg C ha-1 yr-1 (young cocoa systems) to 4.9 Mg C ha-1 yr-1 (old cocoa systems) on conventional farms. Annual litterfall (Org. 12.4 Mg ha-1 yr-1 vs. Con. 12.7 Mg ha-1 yr-1) and nutrient deposition through litterfall were similar on both organic and conventional cocoa farms. The contribution of shade tree species to nutrient return via litterfall was more pronounced in organic systems than conventional systems. Organic cocoa farms had a greater rate of leaf litter decomposition (k = 1.9) than conventional cocoa systems (k = 1.3). Similarly, the rate of macro- and micro-nutrient mineralization was consistently greater on cocoa farms under organic management compared to those under conventional management. The time required for 99% mineralization of nutrients (t99) in leaf litter ranged from 1.30 (Fe) to 2.22 years (Ca) on organic cocoa farms versus 1.84 (K) to 3.22 years (Ca) on conventional cocoa farms. Organic management enhanced the physico-chemical properties of soils compared to conventional management; soil moisture content and electrical conductivity were consistently greater on organic cocoa systems than conventional cocoa systems. Similarly, organic farms had significantly higher stocks of P (51.0 kg ha-1), Mn (310 kg ha-1) and Cu (0.4 kg ha-1) at the 0-30 cm depth compared to conventional farms (28.1 kg ha-1, 165 kg ha-1 and 0.1 kg ha-1, respectively). Annual cocoa pod production per tree was similar for both organic and conventional farms (10 pods per tree for both farm types). However, the overall cocoa pod production was greater on conventional farms (12,433 ha-1 yr-1) than organic farms (9,560 ha-1 yr-1) due to greater cocoa tree density (Org. 1012 ± 40 stems ha-1 vs. Con. 1203 ± 40 stems ha-1). The annual production of banana (Musa sapientum L. f. thomsonii King ex Baker) and plantain (Musa paradisiaca L.) was significantly greater in organic cocoa systems (186.3 kg ha-1 yr-1) than conventional systems (31.6 kg ha-1 yr-1). The results emphasize the potential of smallholder organic cocoa systems to ensure environmental sustainability and long-term cocoa productivity. The adoption of organic management in smallholder cocoa systems is therefore recommended.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Sjogersten, Sofie
Lomax, H. Barry
Dawoe, Evans |
| Keywords: |
Agroforestry, organic farming, cocoa, nutrient recycling, carbon sequestration, biodiversity, soil nutrients, soil properties, agroecology, shade trees, sustainable cocoa production, conservation, Ghana, carbon stocks, litter decomposition, litterfall, REDD+ |
| Subjects: |
S Agriculture > S Agriculture (General) |
| Faculties/Schools: |
UK Campuses > Faculty of Science > School of Biosciences |
| Item ID: |
59384 |
| Depositing User: |
ASIGBAASE, MICHAEL
|
| Date Deposited: |
04 Oct 2023 09:02 |
| Last Modified: |
04 Oct 2023 09:10 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/59384 |
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