Biochar preparation from Parthenium hysterophorus and its potential use in soil application

Abstract

Besides soil carbon sequestration, thermal conversion of weeds like Parthenium hysterophorus to biochar would be a sustainable weed management strategy. Parthenium was charred at different temperature (200–500°C) and residence time (30–120min). With increase in temperature, biochar yield decreased, whereas the stability increased. Stable organic matter yield index (SOMYI) was higher at 300–350°C temperate with 30–45min residential time. Elemental analysis, TGA, and FTIR, indicated the aromaticity and stability of biochar carbon. GC–MS spectra showed that ambrosin, an allelochemical present in Parthenium was lost during pyrolysis. Laboratory experiments on effect of Parthenium biochar (PBC) on soil microbial activity and Zea mays showed an increase in seedling vigour index with PBC addition. Soil dehydrogenase activity (DHA) increased (P<0.05) from 5g/kg PBC onwards; catalase activity increased at lower doses (1 and 3g/kg PBC). Hydrolytic enzyme activities decreased with PBC application. Active microbial biomass carbon was 1.4, 1.7, and 2.1 times higher than control at 1, 3, and 5g/kg PBC treatments, respectively. Basal soil respiration progressively increased up to 20g/kg PBC. The stress indicator or the metabolic quotient decreased with PBC application and no adverse effect was observed even at the highest rate of PBC addition.