Biochar and Crop Residue Amendments on Soil Microbial and Biochemical Properties

Abstract

Biochar amendment to soil is a proposed strategy to enhance soil C sequestration and soil fertility. However, to date, knowledge about the specific effects of biochar on soil microbial community, instrumental for soil C dynamics and nutrient cycling is poorly explored. This study evaluates the comparative effect of two doses (equivalent to 2 and 5 t C ha−1) of each of pine needle biochar, Lantana biochar, wheat residue and lentil residue on soil microbial community in a pot culture study at Pantnagar, India. Energy dispersive X-ray spectroscopy revealed higher C content of biochar than that of crop residues. Evaluation of biochemical quality of the biochars and crop residues through acid hydrolysis reflected high recalcitrance indices of C and N of both pine needle biochar and Lantana biochar. Phospholipid fatty acid (PLFA) analysis indicated that PBC at 5 t C ha−1 recorded the highest Gram-positive bacteria and fungi whereas the highest fungi/bacteria ratio was found with the same dose of Lantana biochar. Lentil residue at 5 t C ha−1 recorded the highest Gram-negative bacteria. Principal component analysis of PLFA also distinctly separated biochar and crop residue treatments. Pearson correlation coefficients indicated that particulate organic carbon served as the carbon and energy sources for Gram-negative bacteria, whereas the Gram-positive bacteria and fungi utilized the more recalcitrant fraction of total organic carbon of soil. Pine needle biochar at 5 t C ha−1 reflected the best sustainable co-existence of bacteria and fungi as compared to other treatments.