Investigation of biochar application in the growth enhancement of Oryza sativa and the associated soil microbial ecology through PLFA characterization

Abstract

In this study, biochar was produced in a Top Lift Up Draft (TLUD)gasifier system from three types of biomass feedstock viz; fruits of Cassia fistula and Caesalpiniasp. and barks of Eucalyptus globulus. The samples of the obtained biochars were characterizedfor pH,physio-chemical properties, surface morphology and surface functional groups. The obtained
biochar samples were further studied for their plant growth enhancement properties including on germination studies and effect on shoot and root growth of rice plants. Furthermore,
combinations of urea and biochar application on the soil were also studied for its effect on plant growth enhan cement. Biochar produced from Cassia fistula fruits at 1.5% concentration increased the plant shoot height 18% higher than the control plants.Eucalyptussp. barks’ biochar application at 0.5% concentration also increased the plant shoot height 12% longer than the control. However,the biochar produced from Caesalpinia sp did not result in increase in shoot length. Yet,a comprehensive increase in root length was observed with the application of biochar. The combined application of nitrogen fertilizer urea) and biochar together reverted the effect of biochar on the shoot length increase. The reasons could be adsorption of nitrogen on the biochar or increased efflux of N2O that affect the nitrogen metabolism in plants. Phospholipid- derived Fatty acid (PLFA) characterization of soil revealed that soil biota shifts when soil was supplemented with the biochar. The bacterial community increased,and a loss of fungal community was observed with the application of biochar. However,the application of biochar and nitrogen fertilizer combination increased the fungal community rather than the bacterial community. This increase in the fungal community could be due to the indirect effect of biochar on soil physio-chemical characteristics.