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University of Namibia (2008)

Sustainable management of Harpagophytum procumbens and the effect of effective micro-organisms and sulphuric acid on its seed germination

Mowa Mowa Edgar

Titre : Sustainable management of Harpagophytum procumbens and the effect of effective micro-organisms and sulphuric acid on its seed germination

Auteur : Mowa Mowa Edgar

Université de soutenance  : University of Namibia

Grade : Master of Science in Biodiversity Management and Research 2008

Résumé
Devil’s claw (Harpagophytum procumbens) is a geophyte that occurs mainly in Central, East and South eastern Namibia where it was previously regarded as a nuisance due to its fruit-claws getting caught on sheep and other livestock. The species has been exploited due to its medicinal properties leading to concerns regarding its sustainability. Efforts to conserve it have been tried in order to understand conditions suitable for its management but there are still poor results in the germination of the species’ seeds and an inconclusive debate about the resting period between harvests which would be considered to be sustainable for the plant. There is also little known about the influence of parent tuber size, and fencing on the plant’s fruit and secondary tuber production. Moreover, the correlation between the number and length of Harpagophytum procumbens branches and the number of its fruits have received less research attention. There is also a lack of knowledge on correlations between above-ground basal cover and below-ground root mass, below-ground root mass and tuber production in Harpagophytum procumbens A study was carried out at Ben-Hur and Vergenoeg farms in central eastern Namibia to investigate the above mentioned concerns The number and weight of secondary tubers were found to increase with parent tuber sizes even though fruit production was found not to be influenced by age. Harpagophytum procumbens plants that were protected from grazing produced more fruits, and more secondary tubers that were large in size. There was a positive correlation between above ground basal cover by other plants and below-ground root mass which negatively correlated with the number and weight of secondary tubers, suggesting that competition with specifically long-rooted shrubs is a threat to maximum tuber production in Harpagophytum procumbens Seeds pre-treated in Effective Microorganisms (EM) resulted in a germination rate of 32, whilst those pretreated with H2SO4 germinated to 17 compared to 5.3 that germinated from the control. The combination of EM and H2SO4 resulted in a lower germination percentage than as expected It is concluded that fruit production in H.procumbens is neither influenced by the period a plant is left without harvesting, nor by parent tuber size,but rather by protection of H.procumbens from grazing. The study therefore recommends fencing for stakeholders who wish to maximize fruit production of the species The study also concludes that five years of not harvesting H.procumbens produces more and large secondary tubers than two years. It is therefore recommended that H.procumbens should not be harvested after every two years but rather after five years when the plant is able to produce more and larger secondary tubers. A shifting harvesting practice is therefore recommended for sustainable management of H.procumbens The study further concludes that protection of H.procumbens from grazing benefits the plant to produce more and lager secondary tubers which subsequently benefit involved stakeholders The study recommends fencing of H.procumbens during their active season and allowing animals to forage again when the plants are dormant The study also concludes that H.procumbens with larger parent tubers produce more and larger secondary tubers. The study recommends that even after not harvesting H.procumbens for five years whilst protecting the plants from grazing when they are active, parent tuber diameter must be what determines the choice of plants to be harvestedIt is also concluded that the presence of shrubs around H. procumbens is a threat because their long roots negatively correlate with the number and weight of secondary tubers. It is therefore recommended that shrubs be removed around H.procumbens, leaving grasses which were found to coexist wit H.procumbens Lastly, the study concludes that sulphuric acid and effective micro-organisms enhance germination in H.procumbens. It is therefore recommended that the two treatments be considered to H.procumbens stakeholders who have been struggling with germination of the species.

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