Influence of Rice Straw Incorporation on the Microbial Biomass and Activity in Coastal Saline Soils of Bangladesh

Abstract

Coastal soils of Bangladesh are affected by salinity. This study investigated salinity as a stress factor on coastal soils in Bangladesh. It was also observed if incorporation of rice straw could remediate negative impacts of soil salinity (if any) on microbial activ-ity. The microbial biomass carbon ranged from 137.85 to 614.88 μg/g among the soils (n = 11). Microbial biomass carbon content and number of both cultivable bacteria and fungi decreased in the soils with higher EC e s (electrical conductivity). Respiration was measured over 30 days with each soil pre incubated at 50% of water holding capacity. Basal respiration rate as well as soil organic carbon content ( r = 0.88, p < 0.05) increased with increasing ECe of soils. The cumulative basal soil respiration was higher in the soils with higher salinity (4.81 - 37.73 mS/cm) (12.91 - 16.89 mg CO2/g dry soil) than in the nonsaline soils (0.98 - 2.33 mS/cm) (5.79 - 6.51 mg CO2/g dry soil). Application of rice straw at 0.50%, 1.00%, 1.50% and 2.00% reduced the negative impact of soil salinity especially at higher EC e s (6.63 - 37.73 mS/cm). Application of 1.00% rice straw appeared to be acceptable for successful amelioration of saline soils of the study area.