Abstract:
Coconut plantations have been identified as common cultivation providing a
significant contribution to the economy of coastal communities. However,
considering the coconut plantations as a coastal ecosystem, information on the
carbon storage in the soil is scanty. Therefore, the current study aimed to fill that
knowledge gap by assessing the Soil Organic Carbon (SOC) stock of coastal
coconut plantations in Southern coast of Sri Lanka. Soil samples (189) were
collected from selected coconut plantations in Galle, Kalametiya, and
Hambanthota areas (5-soil-cores; 45-soil-samples, each site) while another set of
soil samples was collected from mangrove vegetation’s in Galle (6-soil-cores; 54-
soil-samples) for comparison, as mangroves identified as the most carbon-rich
ecosystem in the world. Soil samples were taken using a soil corer
(diameter=4.8cm, depth=1.8m), following random sampling approach. The SOC
contents of the soil samples (5g) were analyzed in triplicates using the Loss On
Ignition (LOI) method. Wilcoxon signed-rank test was performed to analyze data
using R-statistical software. Results showed that the average SOC contents of
coconut plantations in Galle, Kalametiya, and Hambanthota were
150.51(±44.09), 130.12(±87.00), and 143.91(±13.36) Mg C/ha respectively. The
average SOC content of mangroves was 861.95(±131.3) Mg C/ha. According to
the analysis, SOC content in coconut plantations was significantly lower (p<0.05)
compared to mangroves. Less variation was observed for SOC contents in
coconut plantations between sites. The SOC content of adjacent coconut
plantations was estimated 16% of that of SOC content in mangroves. Therefore,
as a win-win step, coconut plantations are recommended for non-productive
coastal areas (e.g., coastal bare-lands, underutilize-areas) considering their
economic importance and carbon science.
