Friday, September 13, 2013

New paper finds sugarcane plantation is a net source of CO2 to the atmosphere

A new paper published in Agricultural and Forest Meteorology finds a sugarcane plantation in Brazil acts as a net source of CO2 to the atmosphere. The paper adds to several other peer-reviewed papers finding various agricultural and ocean sites act as net sources of CO2 rather than sinks.

Fluxes of CO2 above a sugarcane plantation in Brazil

  • a Embrapa Meio Ambiente, CEP 13820-000, Jaguariúna, SP, Brazil
  • b Universidade de São Paulo, R. do Matão 1226, CEP 05508-090, São Paulo, SP, Brazil
  • c Centre for Ecology and Hydrology, Wallingford OX10 8BB, United Kingdom


Seasonal variability of CO2 fluxes in a sugarcane perennial bioenergy crop.
Net carbon balance was measured during two climatically contrasting years.
The dependence of CO2 exchange from light and saturation deficits.
Water use efficiency during the main growth phases of a sugarcane bioenergy system.


Fluxes of CO2 were measured above a sugarcane plantation using the eddy-covariance method covering two growth cycles, representing the second and third re-growth (ratoons) harvested with stubble burning. The total net ecosystem exchange (NEE) in the first cycle (second ratoon, 393 days long) was −1964 ± 44 g C m−2; the gross ecosystem productivity (GEP) was 3612 ± 46 g C m−2 and the ecosystem respiration (RE) was 1648 ± 14 g C m−2. The NEE and GEP totals in the second cycle (third ratoon, 374 days long) decreased 51% and 25%, respectively and RE increased 7%. Accounting for the carbon emitted during biomass burning and the removal of stalks at harvest, net ecosystem carbon balance (NECB) totals were 102 ± 130 g C m−2and 403 ± 84 g C m−2 in each cycle respectively [positive values indicate a net source]. Thus the sugarcane agrosystem was approximately carbon neutral in the second ratoon. Yield in stalks fresh weight (SFW) attained the regional average (8.3 kg SFW m−2). Although it was a carbon source to the atmosphere, observed productivity (6.2 kg SFW m−2) of the third ratoon was 19% lower than the regional average due to the lower water availability observed during the initial 120 days of re-growth. However, the overall water use efficiency (WUE) achieved in the first cycle (4.3 g C kg−1 H2O) decreased only 5% in the second cycle.

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