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Surface organic carbon enrichment to explain greater CO2 emissions from short-term no-tilled soils

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Relation http://oar.icrisat.org/8673/
http://dx.doi.org/10.1016/j.agee.2015.02.001
 
Title Surface organic carbon enrichment to explain greater CO2 emissions from short-term no-tilled soils
 
Creator Chaplot, V
Abdalla, K
Alexis, M
Bourennane, H
Darboux, F
Dlamini, P
Everson, C
Mchunu, C
Muller-Nedebock, D
Mutema, M
Quenea, K
Thenga, H
Chivenge, P
 
Subject Soil Science
 
Description The impact of agricultural practices on CO2 emissions from soils needs to be understood and quantified to
enhance ecosystem functions, especially the ability of soils to sequester atmospheric carbon (C), while
enhancing food and biomass production. The objective of this study was to assess CO2 emissions in the
soil surface following tillage abandonment and to investigate some of the underlying soil physical,
chemical and biological controls. Maize (Zea mays) was planted under conventional tillage (T) and
no-tillage (NT), both without crop residues under smallholder farming conditions in Potshini, South
Africa. Intact top-soil (0–0.05 m) core samples (N = 54) from three 515m2 plots per treatment were
collected two years after conversion of T to NT to evaluate the short-term CO2 emissions. Depending on
the treatment, cores were left intact, compacted by 5 and 10%, or had surface crusts removed. They were
incubated for 20 days with measurements of CO2 fluxes twice a day during the first three days and once a
day thereafter. Soil organic C (SOC) content, soil bulk density (rb), aggregate stability, soil organic matter
quality, and microbial biomass and its activity were evaluated at the onset of the incubation. CO2
emissions were 22% lower under NT compared with T with CO2 emissions of 0.90.10 vs 1.10.10mg
C–CO2 gC1 day1 under NT and T, respectively, suggesting greater SOC protection under NT. However,
there were greater total CO2 emissions per unit of surface by 9% under NT compared to T (1.150.03 vs
1.050.04 g C–CO2m2 day1). SOC protection significantly increased with the increase in soil bulk
density (r = 0.89) and aggregate stability (from 1.70.25mmto 2.30.31, r = 0.50), and to the decrease in
microbial biomass and its activity (r =0.59 and 0.57, respectively). In contrast, the greater NT CO2
emissions per m2 were explained by top-soil enrichment in SOC by 48% (from 12.40.2 to
19.10.4 g kg1, r = 0.59). These results on the soil controls of tillage impact on CO2 emissions are
expected to inform on the required shifts in agricultural practices for enhancing C sequestration in soils.
In the context of the study, any mechanism favoring aggregate stability and promoting SOC allocation
deep in the soil profile rather than in the top-soil would greatly diminish soil CO2 outputs and thus
stimulate C sequestration.
 
Publisher Elsevier
 
Date 2015
 
Type Article
PeerReviewed
 
Format application/pdf
 
Language en
 
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Identifier http://oar.icrisat.org/8673/1/Agriculture%2CEcosystems%20and%20Environment_203_110%E2%80%93118_2015.pdf
Chaplot, V and Abdalla, K and Alexis, M and Bourennane, H and Darboux, F and Dlamini, P and Everson, C and Mchunu, C and Muller-Nedebock, D and Mutema, M and Quenea, K and Thenga, H and Chivenge, P (2015) Surface organic carbon enrichment to explain greater CO2 emissions from short-term no-tilled soils. Agriculture, Ecosystems & Environment, 203. pp. 110-118. ISSN 0167-8809