Impact of agricultural land use on soil organic carbon sequestration at sub-catchment scale

D D A E Hemamali,B L W K Balasooriya,S I Nimanthi,U W A Vitharana,W S Dandeniya,C P Attanayake

doi:10.4038/tar.v31i1.8340

D D A E Hemamali, B L W K Balasooriya + Show 4 more

Open Access

https://doi.org/10.4038/tar.v31i1.8340

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Abstract

Soil organic carbon (SOC) pool determines the potential of soil to perform ecosystem services and maintain climatic stability. Land use plays a significant role in determining the carbon (C) sequestration in soil. This study aimed to determine the impact of long-term agricultural land uses on SOC and other physico-chemical properties and to determine interrelationships between SOC stock and topographic variables at sub-catchment scale in upcountry of Sri Lanka. Soil samples were collected from surface (0-30 cm) and subsurface (30-60 cm) at 109 locations from vegetable (n = 42), tea (n = 44) and forest (n = 23) land uses in a sub-catchment (360 ha) in Nuwara Eliya. Average SOC in different land uses were compared by analysis of variance followed by Tukey post-hoc mean comparison. The largest surface SOC stock was observed in forested area (71.8 Mg/ha) followed by vegetable lands (61.8 Mg/ha) and it was significantly lesser in tea lands (50.7 Mg/ha). The forest soils showed the largest subsurface SOC stock (67.1 t/ha) as well, followed by tea (64.8 Mg/ha) and vegetable (57.9 Mg/ha) land uses. No significant relationship was observed between SOC stock and topographic variables, namely elevation, slope, wetness index and stream power index. This study concludes that the land use is a key determinant of the spatial heterogeneity of SOC and forest have the greater ability of sequestering C compared to vegetable and tea land uses in the studied sub-catchment area.

Highlights

Soils are the largest global terrestrial pools of organic C which stores about two times the carbon stored in above-ground biomass (Batjes and Sombroek, 1997)
Significantly higher soil pH was observed in both surface (5.46) and subsurface (5.03) soils in vegetable lands which could be due to the neutralization resulted through liming materials applied by farmers
Comparable Soil organic carbon (SOC) contents were observed in subsurface soils of forest and tea land uses

Summary

Introduction

Soils are the largest global terrestrial pools of organic C which stores about two times the carbon stored in above-ground biomass (Batjes and Sombroek, 1997). Soil organic carbon has received worldwide attention due to the important role played in the global C cycle and its potential feedbacks on the global warming. Carbon sequestration that describes the process of capturing and long-term storage of atmospheric carbon dioxide helps to mitigate global warming and avoid climate change. The "4 per mille” is a global concept which intends to increase the soil organic matter and carbon sequestration through agricultural practices (Minasny et al, 2017). Anthropogenic interferences can alter the carbon cycle causing negative feedbacks on SOC stock. It is believed that land use change is the second main cause of carbon emission after fuel consumption (Watson et al, 2000)

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