The Natural Fix?

TROPICAL AGRICULTURE

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.

Conventional agriculture: pasture

Agroforestry system

Net C uptake (photosynthesis minus respiration)

1.5 - 3.5

Net C uptake (photosynthesis minus respiration)

0,2

C emission (by erosion, food production)

C emission (by erosion, food production and decay of slash)

C stored in above-ground biomass

82

C stored in above-ground biomass

4

C stored in below-ground biomass

C stored in below-ground biomass

1

18

C stored below-ground (soil and biomass)

C stored below-ground (soil and biomass)

42

63

Carbon fluxes and stocks (Tonnes of C per ha per year for fluxes, tonnes of C per ha for stocks)

Source: Kirby and Potvin, 2007

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.

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