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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-NAGGAR^1,2, A. R. USMAN^1,3

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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