Biochar and short-term n2 o and co2 emission from plant residue-amended soil with different fertilisation history

Abstract

The effect of biochar application on nitrous oxide (N2 O) and carbon dioxide (CO2 ) emissions from an arable soil amended with maize leaves was studied in a laboratory experiment using soil samples collected from plots with three different fertiliser treatments: no fertilisation (CONT), mineral fertiliser (NPKMg) and farmyard manure (FYM), of a well characterized agricultural experiment established in 1949. Two biochars (BC) used in the experiment were produced in low temperature slow (BCslow) and in high temperature fast (BCfast) pyrolysis, and applied at a rate of 10 t ha-1. Different fertilisation strategies induced significant differences in the soil total carbon (C) and nitrogen (N) contents (CONT < NPKMg < FYM), but at the time of the soil sample collection the soil contained low levels of plant-available nitrogen (<10 mg kg-1 N soil) independent of the fertilisation treatment. A stable suppressive effect of BCslow, but not BCfast application on N2 O emissions was found for maize leaves-amended soil. The short-term effect of residue application on N2 O emission was much stronger than the 60-year difference in the soil fertilisation strategy. Mixing of biochar with maize leaves and the soil was in general more efficient in reducing N2 O emissions than biochar application in layers. Neither of the studied ways of biochar application to the soils systematically reduced CO2 emissions. Compared to BCslow, application of thermally more labile BCfast with wider oxygen and carbon (O:C) and hydrogen and carbon (H:C) ratios did not systematically reduce N2 O emissions and increased CO2 fluxes from the soils, underpinning the role of biochar stability and composition for controlling plant residue-related greenhouse gas (GHG) emissions.