EFFECTS OF SOIL TEXTURE ON CHEMICAL COMPOSITIONS, MICROBIAL POPULATIONS AND CARBON MINERALIZATION IN SOIL

Abstract

Soil texture plays a key role in carbon storage and strongly influences nutrient retention and availability. The objective of this study was to 1) determine the effects of soil texture on soil chemical compositions and abundance of microbial communities in soils collected from nine different localities of Sulaimani governorate, 2) the correlation between mineralization of carbon and tested parameters. After analysis, soils were classified into six textural classes (sandy loam, loamy sand, silty loam, silty clay loam, clay loam and loam) which are of significant (p≤0.01) effects on concentration of most soluble ions (Ca+2, K+, HCO-3, Cl- and SO4=), and other soil chemicals (PO-4, CaCO3, organic matter and total nitrogen contents); as well as, the distribution of soil bacterial population. Results of carbon mineralization, using CO2 respiration method under laboratory conditions indicate that rates of CO2 in fine soil textures (viz: clay loam, loam and silty clay loam), are significantly (p≤0.01) higher than coarser soil textures (silty loam, loamy sand and sandy loam). Meanwhile, mineralization rates showed a significant positive correlation with the amount of soil organic matter, and total nitrogen content (r=0.62, r=0.61), respectively. In conclusion, this study indicates that (i) the capacity of soils to preserve soil organic matter and total nitrogen in clay and silt sized particles is greater than sandy one, (ii) abiotic factors such as soil texture; chemical components had a marked influence on the structure and activity of microbial population and mineralization of carbon.