Estimation of net carbon sequestration potential of citrus under different management systems using the life cycle approach
Date
2013-04-15
Authors
Bwalya, jackson Mwamba
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Abstract
A study was conducted to determine the net carbon sequestration potential of citrus to
mitigate climate change. Perennial crops such as citrus have the potential to absorb and
sequester carbon dioxide from the atmosphere, save for the carbon released back through
the application of agro-chemical inputs and use of fossil fuels in running farm machinery
in the management of citrus production systems. The main objective of this study was to
determine the net carbon sequestration potential of sweet orange (Citrus sinensis (L.)
Osbeck), orchards under different management systems. The biomass densities and the
carbon stocks (carbon sequestration) of citrus trees were determined and orchard carbon
emissions estimated and converted to carbon equivalents. Carbon stocks were estimated
using standard carbon inventory methods. Allometric equations were used to transform
citrus tree diameter into biomass. Farmers from the ten fields used in this study analysis
were asked over input application history to the orchards. Life cycle assessment based
carbon foot-printing methods were used to determine citrus orchard carbon emissions.
The carbon emission factors were calculated in conformity with PAS 2050. Results
obtained showed that citrus trees carbon sequestration in biomass ranged from 23.99 Mg
CO2e/ha for young trees to 109 Mg CO2e/ha for mature trees.
The carbon emissions from fertilizer, pesticides, water, electricity and fuels production,
delivery and use was estimated to range from 0.22 Mg CO2e/ha for low input orchards to
4.28 Mg CO2e/ha for high input management. The net carbon sequestration potential
were calculated to be between 15.35 Mg CO2 eq/ha and 95.14 Mg CO2 eq/ha for input
application ranging from two years to 16 years. Continous application of agro-chemical
inputs beyond the optimum fruit bearing age could result in net carbon emissions and is
not justified. The carbon sequestered (biomass accumulation) in trees was observed to
increase with age (r2 = 0.55) and was not seen to increase directly with the increase in
carbon emissions (r2 = 0.44), but it was apparent that increase in inputs especially
fertilizer, pesticides and electricity resulted in increased greenhouse gas emissions. An
opportunity exist in the growing of citrus especially with low input management and
under well managed high input management systems to mitigate climate change by
reducing CO2 from the atmosphere through carbon sequestration in citrus biomass.
Description
Keywords
Citrus fruits--Zambia