Effect of a low rank coal inoculated with coal solubilizing bacteria for the rehabilitation of a saline-sodic soil in field conditions

Abstract

The aim of this research was to assessing changes on some chemical, biological and physical properties of a Salidic Calciustolls, in response enhanced by treatment with low rank coal (LRC) and coal solubilizing bacteria (CSB): Bacillus mycoides, Microbacterium sp and Acinetobacter baumannii, that release humified organic matter (HOM) due to biotrasnsformation of this coal. Over field conditions, plots of 5m2 were treated with the addition of LRC at a dose of 5kg/m2 and the inoculum of coal solubilizing bacteria in suspension of 1x108 bacteria.mL-1 at a dose of 100 mL/m2. Soil respiration, microbiological activity, lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase (Lac) enzyme activities were determined. The variables associated with saline sodic soils (electrical conductivity – EC, sodium adsorption ratio – SAR and exchangeable sodium percentage – ESP), cation exchange capacity (CEC) and bulk density (BD) also were determined. The LRC application contributed to the decrease of EC, SAR and ESP, but were not observed significant changes in pH. No significant changes were found in the BD; however, treatment was able to increase soil respiration, microbiological activity, and stimulation of LiP, MnP and Lac enzymes activity, as well as an increase in soil CEC. These results suggest the possibility of using the LRC as HOM source for the rehabilitation of degraded saline soils, considering that this kind of involvement is a common problem in soils of the Cesar River Valley in the Colombian Caribbean dry lands influenced by coal mining opencast. Keywords: lignite, humic substances, biotransformation coal, soil salinity