Processes Determining the Sequestration and Maintenance of Carbon in Soils: A Synthesis of Research from Tropical India

Abstract

Soil organic carbon (SOC) is the major determinant of soil quality, and it greatly influences global carbon cycling and climate change. This paper is a synthesis of the literature on soil carbon research in India, including soil organic and inorganic carbon stocks, in the form of thematic maps for national and regional level planning at bioclimatic systems and agroecological subregion levels in the country. The potential role of soils in mitigating the global warming effects of atmospheric CO2 is discussed using results from Indian tropical soils. The database on Indian soils collected through natural resource inventory and soil carbon and crop modeling approaches show that sequestration of atmospheric CO2 occurs as pedogenic carbonates and plays role as a soil modifier in enhancing soil organic carbon in the drier parts of the country through management interventions. Clearly, soils can act as a potential medium for sequestering atmospheric CO2 to mitigate the global warming effect.

ICRISAT, India Soils:Yesterday, Today and Tomorrow

“…Manmool Fine, mixed, isohyperthermic, Fluventic Ustropepts intersecting slickensides 19 . These are formed in basaltic alluvium in the valleys showing slow permeability.…”

“…It seems that the cropping and crop management practices in both these soils reduced the rate of formation of pedogenic CaCO 3 and the subsoil sodicity 26 . This scenario of soil resilience suggests how important it is to keep soil and land under vegetative cover to mitigate the adversity of the SAT climate 19 .…”

“…This suggests that these red soils have a potential to sequester >1% SOC even in the semiarid climatic conditions. The major problem in the SAT is the formation of pedogenic CaCO 3 (refs 11, 28) which triggers other associated soil problems 19 that affect crop performance. Over time CaCO 3 formation is considerable and seems stabilized within 0-30 cm depth of black soils (Figure 6 d).…”

“…This is also reflected in reduced Ca/Mg ratio in soils (Figure 6 g). Concentration of extractable Mg down the depth of soil along with extractable Na, especially in red soils (Figure 6 i) indicates the initiation of subsurface sodicity which might affect the entire soil if management intervention is not adopted in SAT areas 11,19,26,28 . Cation exchange capacity is controlled by soil colloids (mostly clay) and organic matter.…”

“…However, the values shown under interventions in these figures emanate from the experience gathered in red and black soil research over the years 19,20,23,26,40 . Our observations suggest a progressive development of subsoil sodicity due to increase in pedogenic carbonates (PCs) under SAT environment with time when anthropogenic activities in terms of sustainable management interventions to raise agricultural crops are not made ( Figure 12).…”