Studies on the ecology, conservation, cultivation and management potential of thaumatococcus daniellii for agroforestry systems

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As the healthiness of chemical sweeteners is often questioned, there is an anticipated increased demand for natural sweeteners like thaumatin, which is obtained from Thaumatococcus daniellii. Studies were therefore conducted on the conservation, site conditions, provenances, growth performance, yield potential of leaves and fruits as well as integration of T. daniellii into Agroforestry systems. The first study was conducted in the Western Region of Ghana on soil characteristics, fruit sources and conservation of T. daniellii in off reserves. Soil pH, N, P, K, Ca, Mg, Total base saturation and Effective cation exchange capacity and organic matter differed significantly among sites. Soil texture significantly differed among sites and ranged from silt loam to sandy loam. Major sources of fruits were predominantly from seven communities within Aowin-Suaman and Wassa Amenfi West districts. Also, no records of conservation, cultivation or integration of T. daniellii into farming systems were obtained for previous or current fruit supplying communities but for Samartex plantations. The second study determined foliage harvesting effects on T. daniellii fruit yield (number and weight), flower production and specific leaf area. The study also estimated potential incomes that could be obtained from leaf and fruit collection. A randomized complete block design was used. Treatments involved harvesting and maintaining a specified petiole population per plot. The percentages of foliage harvest were: No harvesting (Control), 25%, 50% and 75%. Foliage harvest significantly influenced flowering. Mean number of flowers ranked as: Control - 18 > 25% - 6 ≥ 50% - 1 ≡ 75% - 0. No harvest stands produced significantly high number of fruits (11458/ha) compared to 8958/ha for 25%, 4792/ha for 50% and 4583/ha for 75% harvested stands. Total fruit weight ranged v between 59.7 - 127.9 kg/ha. No significant differences in specific leaf area were obtained for all treatments. For both fruit and leaf collection, the highest total income was GH ¢ 24411.36 for 50% followed by GH ¢ 17480.40 for 75%, GH ¢ 15640.33 for 25% harvest stands and GH ¢ 153.48 for the no harvest stand. The third study determined spacing and shade effects on survival, lamina length and width, petiole length and number of tillers. There were three shade levels provided by tree stands: Leucaena (73%), Senna (86%), Carapa (98%) and four spacing treatments: 0.75 m × 0.75 m, 1.0 m × 0.75 m, 1.0 m × 1.0 m, 1.25 m × 1.25 m. Shade significantly (P < 0.001) influenced survival, leaf sizes (lamina widths and lengths), petiole length and number of tillers. Survival were 71% for Leucaena > 60% for Senna > 20% for Carapa. Leaf sizes were also larger for 73% (width-17.6 cm, length-27.1 cm) than 86% shade (width-15.9 cm, length-25.2 cm) and 98% shade (width-11.4 cm, length-18.0 cm) levels. Similarly, significantly longer petioles, 43.6 cm, were obtained for 73% shade compared to 38.8 cm for 86% and 20.4 cm for 98% shade levels. Tillering decreased with increased shade. Similarly, spacing significantly influenced leaf sizes and petiole lengths. The fourth study was on provenances and NPK fertilization on survival, lamina width and length, petiole length and diameter, and tiller production. Provenances differed significantly in lamina length, lamina width, petiole length and petiole diameter. Lamina lengths of provenances were Western-23.7 cm ≡ Volta-21.1 cm > Ashanti-17.2 cm. Lamina widths were Western-14.3 cm ≡ Volta-12.9 cm > Ashanti-9.0 cm. Petiole lengths were Western-37.7 cm ≡ Volta-36.1 cm > Ashanti-24.8 cm. Petiole diameters were Western-5.6 mm ≡ Volta-5.4 mm > Ashanti-3.8 mm. Fertilization also significantly enhanced the growth of lamina width, petiole diameter and tiller production.
A Thesis Submitted to the School Of Graduate Studies, Kwame Nkrumah University of Science and Technology, in partial fulfilment of the requirements for the Degree of Master of Philosophy in Agroforestry,