Pedosphere 25(1): 46--56, 2015
ISSN 1002-0160/CN 32-1315/P
©2015 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Dynamics of CO2 emission and biochemical properties of a sandy calcareous soil amended with Conocarpus waste and biochar
M. EL-MAHROUKY1, A. H. EL-NAGGAR1,2, A. R. USMAN1,3 and M. Al-WABEL1
1Soil Science Department, College of Food & Agriculture Sciences, King Saud University, P. O. Box 2460, Riyadh11451 (Saudi Arabia)
2Department of Soil Science, Faculty of Agriculture, Ain Shams University, P. O. Box 68 Hadayek Shobra, Cairo 11241 (Egypt)
3Department of Soils and Water, Faculty of Agriculture, Assiut University, Assiut 71526 (Egypt)
ABSTRACT
      Biochar is a carbon-rich product obtained by biomass pyrolysis and considered a mean of carbon sequestration. In this research, a sandy calcareous soil from the Farm of the College of Food & Agriculture Sciences, King Saud University, Saudi Arabia, was amended with either woody waste of Conocarpus erectus L. (CW) or the biochar (BC) produced from CW at rates of 0 (control), 10, 30 and 50 g kg-1. The effects of the amendments on soil pH, dissolved organic carbon (DOC), microbial biomass carbon (MBC), CO2 emission and metabolic quotient (qCO2) of the sandy calcareous soil were studied in a 60-d incubation experiment. The results showed that the addition of CW led to a significant decrease in soil pH compared to the control and the addition of BC. The CO2-C emission rate was higher in the first few days of incubation than when the incubation time progressed. The cumulative CO2-C emission from the soil amended with CW, especially at higher rates, was higher (approximately 3- to 6-fold) than that from the control and the soil amended with BC. The BC-amended soil showed significant increases in CO2-C emission rate during the first days of incubation as compared to the non-amended soil, but the increase in cumulative CO2-C emission was not significant after 60 d of incubation. On the other hand, CW applications resulted in considerably higher cumulative CO2-C emission, MBC and DOC than the control and BC applications. With the exception of 0 day (after 1 h of incubation), both CW and BC applications led to lower values of qCO2 as compared to the control. The power function kinetic model satisfactorily described the cumulative CO2-C emission. Generally, the lowest values of CO2 emission were observed in the soil with BC, suggesting that the contribution of BC to CO2 emission was very small as compared to that of CW.
Key Words:  dissolved organic carbon, metabolic quotient, microbial biomass carbon, power function kinetic model, soil pH
Citation: El-mahrouky, M., El-naggar, A. H., Usman, A. R. and Al-wabel, M. 2015. Dynamics of CO2 emission and biochemical properties of a sandy calcareous soil amended with Conocarpus waste and biochar. Pedosphere. 25(1): 46-56.
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