Agriculture Reference
In-Depth Information
carbon, thickness of soil layer and volume
of fraction >2 mm) to calculate the soil car-
bon stocks for Kenya and Upper Tana, re-
spectively.
Kamoni
et al
. (2007) used a modelling
approach using Century and Roth C models
and the Intergovernmental Panel on Climate
Change (IPCC) system to predict soil or-
ganic carbon stocks and changes in Kenya
between 1990 and 2030. Stratified random
sampling of herbaceous standing crops have
been carried out in Nairobi National Park to
estimate the primary production of the
grassland savannah (Desmukh, 1986; Kin-
yamario and Imbamba, 1986), although
their results were not converted to carbon
stocks. The Carbon Benefits Project, devel-
oped between 2009 and 2012 by a consor-
tium of partners including Colorado State
University in collaboration with Kenya,
Brazil, Nigeria, Niger and China, provides
tools to estimate carbon stocks and green-
house gas (GHG) emissions.
atmospheric cycling, or a net positive radiative
forcing that triggers an increase in tem-
perature, which eventually affects climatic
patterns like rainfall, pressure or cyclones,
and later interacts with whole spheres of
the earth (SCC-VI Agroforestry East Africa,
2008). GHGs are the gases released by
human activity that are responsible for cli-
mate change and global warming. Agricul-
ture (through improved management prac-
tices) and forestry provide, in principle, a
significant potential for GHG mitigation.
Improved and sustainable crop husbandry
practices increase productivity, leading to
increased SOC storage (SCC-VI Agroforestry
East Africa, 2008). Examples of agronomic
practices in western Kenya include using
improved crop varieties, extending crop
rotations, notably those with perennial
crops that allocate more C belowground,
and avoiding or reducing the use of bare
unplanted fallow among others. This al-
lows for better vegetation cover, protec-
tion of the soil and spread of the harvest
within the farm. Forests can store
20-100
times more carbon than other vegetation
types on the same land area, or around
30-60
t C ha
-
1
.
Management of Organic
Carbon
Land management practices that increase
net primary productivity, reduce the rate of
heterotrophic respiration, or both, lead to
an increase in ecosystem C storage. Ex-
amples include the planting of trees, redu-
cing the intensity of tillage on cropland or
restoring grasslands on degraded (SCC-VI
Agroforestry East Africa, 2008) land. Soil
fertility improvement increases plant bio-
mass, hence increasing carbon sequestra-
tion (the storage of carbon dioxide usually
captured from the atmosphere), and con-
trols climate change. Decline in soil fertility
causes substantial net losses of soil carbon,
resulting in increased carbon flux to the at-
mosphere. Increasing SOM content can
both improve soil fertility and reduce the
impact of drought, improving adaptive cap-
acity and making agriculture less vulnerable
to climate change, while also sequestering
carbon. Burning of fossil fuels (coal, oil and
gas) and land-use conversion (agriculture, de-
forestation) releases GHGs that influence
Conclusions
Population pressures, declining plot sizes
and resource constraints in Africa have led
to agricultural intensification and continu-
ous cropping with insufficient inputs, lead-
ing to rapid decline in SOC stocks. Sustain-
able management of organic resources will
require interventions by regional govern-
ments to help farmers access inputs cheaply,
as well as educating farmers on sustainable
land management practices. Specific strat-
egies to increase the soil carbon pool have
been identified and include degraded land
restoration and vegetative regeneration, no-
till farming, cover crops, organic residues,
composting, nutrient management, manur-
ing, improved grazing, water conservation
and harvesting, efficient irrigation, agrofor-
estry practices and growing energy crops on
fallow land.
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