Abstract:
Mangifera indica (MI), Alstonia macrophylla (AM), and Calophyllum inophyllum (Cl) are
medicinal plants with specific chemical compositions in leaves, roots, stem, and fruits/nuts.
Among these, MI is known to have astringent, acrid, and refrigerant roots ancf bark, whereas
AM and Cl are been reported for the presence of Alkaloids and Flavonoids, respectively, in
stem-bark. These chemicals have specific characteristics that might interfere with and
thereby change some soil properties. The objective of this study was to examine the effects of
woody debris on soil hydrophobicity and wetting behavior using fine woody dusts. Arable top
soil (0 -10 cm) (Udults) used for the experiment was air dried and sieved through 2 mm sieve.
Air dried and ground woody dusts were sieved through 1 mm sieve prior to mixing with
sieved soil to obtain § and 50% contents. Samples were exposed to four temperature levels
(27, 60, 100, and 200°C) for 6 h. Hydrophobicity of soils was determined, in three replicates,
with sessile drop contact angle of a water drop on a monolayer of samples fixed to a glass
slide using a double-sided adhesive tape. Microphotographs of the drops were taken within 1
s by digital microscopic camera. Samples mixed with 5% woody dusts did not show a
measurable contact angle within 1 s due to lateral wetting of the monolayers. Contact angle in
samples with 50% woody dusts was highest with Cl, followed by AM and MI. Presence of
flavonoids might be the reason for Cl to show a high hydrophobicity. The hydrophobicity of
all the samples increased with time after heating which was measured up to 7 d. Contact
angles of samples with 50% woody dusts increased by 12-16° with increasing temperature
from 27 to 100°C. This can be attributed to changes in organic compounds in the woody dusts
with the increasing temperature. Upon exposure to 200°C, hydrophobicity disappeared in all
the samples showing that the organic materials responsible for causing the hydrophobicity
lost either by evaporation or removal as CO2 and H20 .
