Relationship between greenhouse gas emissions and changes in soil gas diffusivity in a field experiment with biochar and lime

Abstract

Reducing greenhouse gas emissions from arable soil while maintaining productivity is a major challenge for agriculture. Biochar is known to reduce N2O emissions from soil, but the underlying mechanisms are unclear. This study examined the impact of green waste biochar (20 Mg ha−1) and lime (CaCO3; 2 Mg ha−1) application on soil gas transport properties and related changes in these to soil N2O and CO2 emissions measured using automated chambers in a field experiment cropped with maize. In situ soil water content monitoring was combined with laboratory measurements of relative soil gas diffusion coefficient (Dp/D0) at different matric potentials, to determine changes in Dp/D0 over time. Cumulative N2O emissions were similar in the control and lime treatment, but much lower in the biochar treatment. Cumulative CO2 emissions decreased in the order: lime treatment > biochar treatment > control soil. When N2O emissions were not driven by excess N supply shortly after fertilisation, they were associated with Dp/D0 changes, whereby decreases in Dp/D0 corresponded to N2O emissions peaks. No distinct pattern was observed between CO2 emissions and Dp/D0. Cumulative N2O emissions were positively related to number of days with Dp/D0 < 0.02, a critical limit for soil aeration. These results indicate that improved soil gas diffusivity, and hence improved soil aeration, may explain the effect of biochar in reducing N2O emissions. They also suggest that knowledge of Dp/D0 changes may be key to explaining N2O emissions.

Review of Large-Scale Biochar Field-Trials for Soil Amendment and the Observed Influences on Crop Yield Variations

“…Biochar application reduced soil N 2 O emissions by decreasing the concentrations of soil labile N forms and hindering the activities of N-cycling enzymes (Song et al, 2019). A field study on maize crop in Switzerland reported that the enhanced soil gas diffusivity in biochar added soil (and thus improved soil aeration), may lead to reduced N 2 O emission (Keller et al, 2019). However, Suddick and Six (2013) found no considerable change in N 2 O flux with the application of biochar and compost.…”

Reduced Nitrous Oxide Emissions From Drained Temperate Agricultural Peatland After Coverage With Mineral Soil

“…To determine the soil pore volume, on 12 April 2019, 72 undisturbed cylindrical soil samples (100 cm −3 ) were collected at three depths (3-8, 18-23, and 58-63 cm) with 12 replications at each site and transferred to the laboratory. In the laboratory, different pore diameters were measured following the approach by Keller et al (2019). For this, samples were saturated from below and then drained to soil matric potentials of −30, −60, −100, −300, and −1,500 kPa.…”

“…Air porosity was calculated based on the difference between volumetric water content (VWC) and total pore volume. The relative gas diffusion coefficient (D p /D 0 ) was calculated based on air-filled porosity by following the approach by Keller et al (2019). A D p /D 0 of 0.02 has been suggested as the critical threshold for adequate soil aeration, and the D p /D 0 value lower than 0.02 indicates insufficient soil aeration (Schjønning et al, 2003).…”

Impacts of agricultural waste and NPK fertilizers on soil chemical properties, production and phosphorus uptake of sweet corn plants on ultisol soil

“…Biochar application reduced soil N 2 O emissions by decreasing the concentrations of soil labile N forms and hindering the activities of N-cycling enzymes [10]. A field study on maize crop in Switzerland reported that the enhanced soil gas diffusivity in biochar added soil (and thus improved soil aeration), may lead to reduced N 2 O emission [11]. However, Suddick and Six [12] found no considerable change in N 2 O flux with the application of biochar and compost.…”