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There is great potential to restore carbon in tropical agricultural soils through manage-
ment practices that, in the right circumstances, can also increase productivity. Agrofor-
estry can offer particularly large carbon gains, although it can increase water demand.
Agricultural carbon sequestration policies will need to be tailored to particular circum-
stances to allow farmers to benefit.
Many agricultural areas in the tropics have suffered severe de-
pletion of their soil carbon stocks. Some soils in tropical agri-
cultural systems are estimated to have lost as much as 20 to 80
tonnes of carbon per ha, most of which has been released into
the atmosphere (Lal 2004a). Soil erosion, tillage and burning
or removal of crop residues and livestock products reduce soil
carbon levels and over time the soils have become degraded,
often resulting in land abandonment.
TROPICAL AGRICULTURE
Conventional agriculture:
pasture
0,2
Net C uptake
(photosynthesis
minus respiration)
4
1
C stored in
above-ground biomass
42
C stored in
below-ground
biomass
C stored below-ground
(soil and biomass)
C emission
(by erosion, food production)
Carbon fluxes and stocks
(Tonnes of C per ha per year for
fluxes, tonnes of C per ha for stocks)
Agroforestry system
1.5 - 3.5
Net C uptake
(photosynthesis
minus respiration)
C emission
(by erosion, food
production and
decay of slash)
C stored in
above-ground biomass
18
63
82
C stored in
below-ground biomass
C stored below-ground
(soil and biomass)
Source: Kirby and Potvin, 2007