Soil carbon sequestration for sustaining agricultural production and improving the environment with particular reference to Brazil
2005
Lal, R.
Agricultural ecosystems generally contain less soil organic carbon (SOC) pool than their potential capacity because of the low return and high rate of mineralization of biosolids, and severe losses due to accelerated erosion and leaching. Conversion of natural to agricultural ecosystems usually causes depletion of 50 to 75 percent of the antecedent SOC pool, thereby creating a potential sink capacity of as much as 35 to 40 Mg C/ha. The depletion of SOC pool leads to decline in soil quality and resilience with attendant reduction in biomass productivity, decreased capacity to degrade and filter pollutants, increased risks of soil degradation by erosion and other processes, and increase in emission of greenhouse gases (GHGs). The magnitude of depletion of SOC pool is greater for soils of the tropics than temperate regions, and for farms which are resource-based and managed with low-input than those managed with science-based and judicious off-farm inputs. The SOC sequestration, increasing SOC pool through conversion to an appropriate land use and adoption of recommended management practices (RMPs), can reverse soil degradation trends, improve soil quality and resilience, increase biomass production and decrease emission of GHGs. A strong link exists between the labile fraction of SOC pool and soil biodiversity-the activity and species diversity of soil fauna (micro, meso and macro) and micro-organisms. Soil biodiversity is usually higher under pastures and planted fallow systems than under crops, and is likely to increase with adoption of conservation tillage and mulch farming, integrated nutrient management and manuring, mixed farming systems and integrated pest management (IPM) techniques. The gross rates of SOC sequestration through adoption of RMPs range from 400 to 800 kg/ha/y for cool and humid regions and 100 to 200 kg/ha/y for dry and warm climates. The potential of soil C sequestration in Brazil is estimated at about 50 Tg C/y. In addition, 60 Tg C/y emitted by erosion-induced mineralization can also be avoided through effective erosion control measures.
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