Soil management strategies to enhance carbon sequestration potential of degraded lands

Abstract

Reclamation of degraded lands has huge potential for carbon(C) sequestration to counteract the climate change. It was estimated that about 1,947 Mha of land is degraded worldwide and in Asia (excluding west Asia), the degraded soils occupied an area of 747 Mha. In India 59.3 Mha of land is degraded. The major land-degrada- tion processes in the World and in Asia are water erosion, wind erosion, salinity and alkalinity, nutrient depletion and metal pollution. Various management strategies like conservation agriculture, integrated nutrient manage- ment, afforestation, alternate land use, plantations and amendments and use of biochar hold promise for long- term C sequestration. It has been projected that in India the largest potential lies in erosion prevention (33.650.4 Tg/year), secondary carbonates and bicarbonates (21.825.6 Tg/ha), agricultural intensification (12.716.5 Tg/ year) and restoration of degraded soils (9.813.9 Tg/ha). Thus, total potential of soil organic C (SOC) sequestra- tion in India is 77.9 to 106.4 Tg/year. Conservation agriculture has tremendous potential on soil C sequestration to the tune of 1.8 t/ha/year during the first decade of adoption. In dryland agriculture, conjunctive use of crop resi- dues and Leucaena clippings had greater effect on C build up. The C sequestration potential of integrated nutrient management (100% NPK + FYM) was at the tune of 0.95 Mg/ha/year under rainfed agriculture. Overall the C se- questration potential of soils under arid and semi-arid climate is lesser than the soils under humid, per-humid climate. Afforestation could have remarkable increase in C sequestration in tropical climate than in either temper- ate of boreal climate. Alternate land use by adoption of agroforestry system is a promising strategy for enhancing the C sequestration by vegetation as well soil. Agroforestry plant species, e.g. Prosopis juliflora (SW.) DC.,) Vachellia nilotica (L.) P.J.H. Hurer & Mabb.; syn. Acacia nilotica, Casuarina equisetifolia L., Tamarix aphylla (L.) Karst.; syn), Tamarix articulate Vahl, Diplachne fusca (L.) P. Beauv. Ex Roem & Schult.; syn. Leptochola fusca which are well adapted to saline and alkali soils are reported to increase in SOC contents. Certain plantations like Stylosanthes guianensis (Aubl.) Sw., Acacia auriculiformis A. Cunn. Ex. Benth. and Dalbergia sissoo DC. hold promise to reclaim acid soils and enhancing SOC content. From long-term fertilizer experiment, it has been proved that balanced fertilization alone (NPK or NPK + FYM) or with lime (NPK + lime) not only reclaim the Alfisols but also enhance SOC content. Biochar, a pyrolysed product of biomass being resistant to microbial decomposi- tion has huge potential for carbon sequestration in soil. The reclamation of degraded land by various means can be promising for C sequestration and it has greater implications on enhancing yield of crops.