Biochar Field Study: Greenhouse Gas Emissions, Productivity, and Nutrients in Two Soils

Abstract

Application of biochar to soil has potential to reduce greenhouse gas (GHG) emissions, store C for long‐term and provide agronomic benefits. However, the extent of these benefits are dependent on the type of biochar used and the environmental system in which it has been placed. While there are a large number of laboratory and glasshouse experiments, the number of biochar field studies is still limited. We conducted a 2‐yr field study to evaluate the effect of a wood‐based (blue mallee; Eucalyptus polybractea) biochar on GHG fluxes, pasture biomass, soil nutrient leaching, and nutrient uptake under different fertilizer rates in two soils (Arenosol and Cambisol) under a perennial pasture. Three rates of biochar were used in full factorial combination with 50 and 100% of the recommended fertilizer rate. Greenhouse gas fluxes (CO2, CH4, and N2O) were measured using static gas chambers on a monthly basis during the first year, then a bimonthly basis during the second year. Pasture biomass, nutrient uptake, and soil solution chemistry were determined on a regular basis over the 2‐yr period. The biochar induced no or minimal effects on GHG fluxes, pasture biomass, nutrient uptake or soil solution chemistry. In most instances, the significant differences between treatments were due to soil type. Fertilizer significantly increased pasture biomass for the first 8 mo, but thereafter there was no effect. There were also no adverse effects from the biochar. This biochar would be most suitable for enhancing soil C storage, as opposed to improving grassland production.Core Ideas A wood‐based biochar was added to two soil types in a 2‐yr field study. Biochar had minimal effect on soil greenhouse gas emissions. Biochar had no effect on plant biomass or soil leachate nutrient concentration.