Preferential Alternatives to Returning All Crop Residues as Biochar to the Crop Field? A Three-Source ¹³C and ¹⁴C Partitioning Study

Abstract

The simultaneous effects of biochar on soil organic matter (SOM, C4) and sweet potato (SP) residue (Ipomoea batatas, C3) mineralization were studied over 180 days via 13C and 14C isotopic label partitioning. Upon concomitant SP residue addition, biochar mineralization decreased by 11% of the total added biochar-C. Compared to positive priming effects induced by biochar amendment alone on SOM (0.46 mg C g–1 soil) at 180 days, amendment solely with SP residues induced significantly larger effects (1.5 mg C g–1 soil). Combination biochar and SP residue addition reduced SOM mineralization by 20.5% and increased SP residue mineralization by 10.1%. Biochar addition caused preferential uptake of SP residues over SOM by microbes. Thus, the lower priming effects on SOM and CO2 emission induced by biochar amendment with or without SP residues compared to that from SP residue addition alone may result in crop residues being partly pyrolyzed to biochar in the cropland.

Realizing United Nations Sustainable Development Goals for Greener Remediation of Heavy Metals-Contaminated Soils by Biochar: Emerging Trends and Future Directions

“…The release of volatiles at high temperatures may explain the impact of pyrolysis temperature on such characteristics. According to many researchers [27][28][29], higher pyrolysis temperatures resulted in a larger biochar surface area, higher pH, and higher percent C content but lower percent N content. As a result, choosing an appropriate pyrolysis temperature involves a tradeoff between the specified surface and chemical characteristics [27][28][29].…”

“…According to many researchers [27][28][29], higher pyrolysis temperatures resulted in a larger biochar surface area, higher pH, and higher percent C content but lower percent N content. As a result, choosing an appropriate pyrolysis temperature involves a tradeoff between the specified surface and chemical characteristics [27][28][29].…”

Biochar—A Panacea for Agriculture or Just Carbon?

“…There have been various studies in which BC produced at lower temperature ranging from 450 to 550 • C stimulated positive priming when added to sandy loam (Table 3). Overall, BC promoted increases in C sequestration, organic carbon retention, SOM, mineralization, phosphorous and potassium content, and plant biomass [136][137][138][139]. Conversely, one study reported a decrease in soil microbial biomass and SOM mineralization when crop residue-derived BC (450 • C) was applied to sandy loam soil [140].…”