Dr Muhammad Riaz1, Mr. Aqeel Ahmad1, Dr. Muhammad Saleem Arif1, Mrs. Samar Fatima1, Dr. Tahirs Yaseem1, Dr. Muhammad Bilal Shakoor1, Dr. Muhammad Rizwan1, Ms. Maryam Adil1, Dr. Shafaqat Ali1
1Department of Environmental Sciences & Engineering, Government College University Faisalabad, Pakistan, Faisalabad, Pakistan
Biochar is a carbon (C) rich material produced from pyrolysis of biomass under no or limited supply of oxygen. Use of biochar for multiple purposes depends on its physico-chemical characteristics-driven stability and decomposition. We investigated abiotic and microbial mineralization of a range of low-pyrolysis temperature (400 °C) biochars at 15, 30 and 45 °C incubation temperatures. Biochars were developed from eucalyptus leaves (ELB), wheat straw (WSB), poultry manure (PMB), cotton sticks (CSB), vegetable waste (VWB), lawn grass (LGB) and citrus leaves (CLB). In addition to elemental composition, biochars were characterized for pH, electrical conductivity (EC), labile organic C (L-OC) and LOC characteristics including specific ultraviolet absorbance (SUVA), aromaticity, hydrophilic and hydrophobic C fractions and total phenolic contents. Carbon mineralization was measured for seven days using abiotic (sterile incubation with mineral nutrients) and microbial (microbial inoculum with mineral nutrients) experimental conditions. We found that abiotic degradation of biochars were generally less than microbial degradation, however, these patterns significantly varied between feedstocks and incubation temperatures. Both abiotic and microbial C mineralization was also strongly controlled by incubation temperatures. However, increase in incubation temperature was not always associated with acceleration in abiotic and microbial CO₂ efflux. Percent C mineralized (PCM) of L-OC was higher under microbial incubation at 30 °C and higher for PMB, CSB and CLB. Water extractable OC (WEOC) also showed significant variations with respect to biochars and incubation temperature whereas WEOC correlated significantly positively with CO₂ efflux under abiotic and microbial incubation conditions. Characteristics of L-OC seem to have strong influence on both abiotic and microbial biochar degradation; positive relationships with pH, volatile matter, L-OC and total phenolics and negative relationships with EC and SUVA. These observations warrant the consideration of abiotic (chemical & photo-oxidation, solubilization) and microbial decomposition of biochars before its application to soils.
Dr. Muhammad Riaz is working as an Associate Professor in the Department of Environmental Sciences & Engineering, Government College University Faisalabad (GCUF), Pakistan. He earned his PhD in Environmental Sciences from the University of York, UK. His research is mainly focused on soil biogeochemistry, CNP cycling in agroecosystems, biochar as a tool for soil C sequestration and soil quality management, and dynamics of soil organic matter cycling and recycling in semi-arid and arid agroecosystems.