Sustainable Management Of Harpagophytum Procumbens And The Effect Of Effective Micro-Organisms And Sulphuric Acid On Its Seed Germination

Abstract

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

harvested.

It 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.