Crop residues under different water regimes
can cause significant alterations in soil organic carbon
fractions, and in turn, soil-atmospheric carbon dioxide
(CO2) emissions. To evaluate the effect of rice straw
application on CO2 emissions and labile organic carbon
fractions under different water regimes, an incubation
experiment was conducted for 90 days. Ten treatments
were developed from the interaction between five water
levels (100, 85, 70, 55, and 40 % of water-holding capacity
(WHC)) with and without incorporation of rice straw.
Peaks of CO2 fluxes were observed after 13 days of rice
straw incorporation, which decreased gradually till the end
of the incubation period. The incorporation of rice straw
caused significant increases in CO2 fluxes by 2.77–2.83
times from the paddy soil. In the presence of rice straw, the
highest CO2 fluxes were generally observed at W3 (70 %
of WHC), whereas the lowest fluxes were occurred at W1
(100 % of WHC). Addition of rice straw under a range of
water regimes markedly improved the transformation of
soil organic carbon and labile organic carbon pools such as
dissolved organic carbon, microbial biomass carbon, light
fraction organic carbon, particulate organic carbon, and
permanganate oxidizable carbon. The significant correlations
between all labile soil organic carbon fractions and
CO2 concentrations confirmed their important roles in the
emission of CO2 from the paddy soil. In summary, the
results suggest that light fraction organic carbon, particulate
organic carbon, and permanganate oxidizable carbon
were more sensitive indicators for CO2 emissions and
organic matter alterations as compared to other carbon
fractions. |
