Characterization of olive pomace biochar produced at different temperatures and their temporal effects on soil aggregation and carbon content

Abstract

The properties of biochar may vary depending on feedstock type and producing temperature. The aim of this research was to understand the short-term effects of different pyrolysis temperatures and application rates of olive pomace biochar (OPB) on soil carbon (C), aggregate stability (AS), and aggregate size distribution for sandy loam soil. OPB was produced at low (350 °C) and high (700 °C) temperatures and incorporated into the soil at different rates and incubated for 6 months under controlled temperature and moisture conditions. OPB350 had low pH, high carbon, and nitrogen (N) values compared to OPB700. As the temperature increased the concentration of zinc, iron, manganese, copper, sodium, potassium, and magnesium in biochar increased. The BET surface area of OPB350 was 1.076 m2 g−1, and OPB 700 was 107.7 m2 g−1. Application of OPB improved soil aggregate stability and carbon content while the proportion of > 4 mm-aggregates and aggregate mean weight diameter decreased. OPB addition to soil increased microaggregate percentages and decreased macroaggregate percentages. OPB produced at high temperatures significantly increased soil AS value compared to OPB350.