Question

What processes/climate/etc. increase or decrease soil carbon sequestration? What are the limits of management practices for sequestering carbon in soils?

Answer 1

Soil Carbon Storage levels result from the interactions of several ecosystem processes, of which photosynthesis, respiration, and decomposition are key. Photosynthesis is the fixation of atmospheric CO2 into
plant biomass. Soil carbon storage input rates are primarily determined by the root biomass of a plant, but also include litter deposited from plant shoots. Soil C results both directly from growth and death of
plant roots, as well as indirectly from the transfer of carbon-enriched compounds from roots to soil microbes.

Technical potential of soil carbon sequestration using recommended management practices
Transfer of atmospheric CO2 into the pedologic pools by use of judicious management of soils and vegetation,
involves numerous agronomic interactions. Principal agronomic techniques include:

• use of crop residues or synthetic materials as surface mulch in conjunction with incorporation
of cover crops into the rotation cycle;
• adoption of conservation-effective measures to minimize soil and water losses by surface runoff and
accelerated erosion bioengineering;

• enhancement of soil fertility through integrated nutrient management (INM) that combines practices
for improving organic matter management (in situ), enhancing soil biological processes involving
biological nitrogen fixation (BNF), and mycorrhizae, and additions of organic wastes (biosolids, slurry)
and synthetic fertilizers;
• conservation of water in the root zone to increase the green water component by reducing losses
through runoff (blue water) and evaporation (grey water), and increasing use efficiency through
application of drip irrigation/fertigation techniques;
• improvement of grazing systems that enhance the diet of livestock and reduce
their enteric emissions; and
• better use of complex farming systems including mixed crop-livestock and agroforestry techniques
that efficiently use resources, enhance biodiversity and mimic the natural ecosystems.