Soil taxonomical classification and organic carbon sequestration potential of coastal acid sulfate soils: Kari and Kayal ecosystems of Kerala, India

A study was carried out to understand the carbon sequestration potential of the coastal acid sulfate soils of wetland agroecosystems Kari and Kayal of Kuttanad, Kerala.

Soil profiles excavated in these lands were studied for their physico-chemical and morphological properties and classified according to USDA based soil taxonomy.

The soils were very deep with moderately deep (97 cm) and moderately shallow (75 cm) solum thickness and both the soils were acidic,sulfuric and/or sulfidic and saline.The BaCl₂ acidity,exchangeable Al,total exchangeable bases and cation exchange capacity were higher in Kari soils.Both the soils recorded high sulfate S,which was higher in Kari soils.Based on the USDA soil taxonomy, Kari soils were classified to ferrihumic, euic, isohyperthermic, Typic Sulfohemists and Kayal soils to loamy, mixed, super-active, isohyperthermic, Salidic Sulfaquepts at the family level.

The organic carbon stock was higher in the sub-surface layer (30-100 cm) which recorded 2769.63 and 645.45 Mgha^− 1 in Kari and Kayal lands respectively. The soil carbon sequestration potential was higher in Kari soils and the highest rate of C sequestration was at the depth 30–60 cm(656.09 kgm^− 3) and soil layer was proved to have the capacity to hold 20.40 TgC with a total of 58.86 TgC in 11,250 ha of Kari lands for a thickness of 150 cm, while Kayal soils recorded the maximum at the depth 60-90 cm (163.43 kgm^− 3) with a capacity to hold 3.29 TgC with a total of 21.02 TgC in 13,000 ha of Kayal lands for a thickness of 150 cm in 13,000 ha of Kayal lands.