High adsorption efficiency of residue-based biochar along with organic fertilizer improves dry matter and yield of pennywort (Centella asiatica L. Urban) by removal of heavy metals

Pennywort [Centella asiatica (L.) Urban] is a herbaceous perennial crop. Heavy metals (HMs) are considered to significantly influence the growth, yield, and quality of pennywort. The present study evaluated the adsorption efficiency of residue -based biochar and organic fertilizer on pennywort dry matter yield and removal of heavy metals (Cd and Pb) within soil -plant system. The laboratory and pot studies were set up in a protected warehouse following randomized complete block design with four replicates. Biochar prepared from pyrolysis of rice husk and peanut shell residues along with organic fertilizer (rice husk+peanut shell) was applied at different rates viz. 0, 1, 2, 3, 4, 5% on weight basis. The dry matter and economic yield, soil and plant HMs contents were recorded using appropriate procedures. Rice husk biochar (RHBC) showed the highest adsorption efficacy in removal of Cd and Pb from soil. This potential of biochar and organic fertilizer was also reflected in pot study where application of these organic adsorbents significantly (p<0.05) reduced the HMs in soil and shoot of pennywort. Application of 5% peanut shell biochar (PSBC) produced highest dry matter yield of pennywort, while application of 5% RHBC reduced Cd by 26.4% and 33.9% Pb from soil and 81.0% Cd and 60.9% Pb in pennywort shoot. Thus, RHBC with high adsorption efficiency can be a promising alternative source in reducing the HMs accumulation in the soil -plant system.