Carbohydrate Distribution of Particle Size Fractions of Soils in Relation to Land-use Types in Mbaise, Southeastern Nigeria

Abstract

Carbohydrate content of soil particle size fractions provides useful information about soil’s capacity for carbon sequestration. Carbohydrate distribution of particle size fractions of soils of cassava, fallow, bare soil and oil palm land use types in Mbaise, Southeastern Nigeria was evaluated using hydrolysis procedures involving concentrated H₂S0₄, dilute H₂S0₄, hot and cold water. Also relationships between extractable carbohydrates by the different reagents, carbohydrate contents of the bulk soil and the soil particle size fractions and that between the bulk soil and soil properties were determined. Top and sub soil carbohydrate contents of the various land uses differed (LSD 0.05), with concentrations varying in increasing order of cold water < hot water < dilute H₂S0₄ < concentrated H₂S0_4. Whereas, the sand fraction was enriched with and contained the largest concentration of water soluble carbohydrate, the clay fraction was more enriched and dominated the other extractable carbohydrate forms (conc. H₂S0₄, dil. H₂S0₄ and hot water soluble). Besides concentrated H₂S0₄ extractable (total) carbohydrate that correlated distinctly (P < 0.05) with hot water (r = 0.55), relationships between extractable carbohydrates by the other reagents were not significant. Bulk soil carbohydrate contents were closely related to the silt (0.90) and sand (0.77) than the clay (0.42) particle size fractions as indicated by the slopes of the regression equations. Carbohydrate concentrations of the sand, clay and silt fractions accounted for 69, 58 and 47% respectively of that in the bulk soil. Soil extractable carbohydrates correlated with different soil properties. The high carbohydrate concentrations and enrichment of the soil clay fractions indicated that much of the carbohydrates existed in the stable forms and not easily accessible for microbial degradation.   

Keywords: Carbohydrate, Particle size fraction, Soils, Land use and Southeastern Nigeria.