Combination of Biochar‐Based Fertilisers and Reactive Barriers Improved Soil Carbon Storage, Soil Moisture Retention, and Crop Yield in Short Term

ABSTRACT Climate change threatens long‐term soil health because of increased severity and frequency of drought periods. Applying biochar to soils before a drought can increase non‐biochar soil carbon (C) and water storage over the long term and sustain crop yield. However, the on‐farm benefit of buried solid biochar and applied liquid biochar at low rates remains uncertain. This study examined the effects of two novel biochar‐based soil amendments on soil C, water storage and crop yield. The biochar‐based amendments included a biochar reactive barrier (RB) made by layering wood‐based biochar, straw mulch and cow manure into a series of open surface trenches, and a liquid biochar mineral complex (BMC) applied twice, at low rate (200 kg ha−1) to one side of RB (fertilised area), while the other side of RB received no treatments (non‐fertilised area). Moisture concentration within the RB ranged from 6.76% up to 56.68% after large rainfall, more than double the surrounding soils and gradually started migrating from the RB outwards. Soil within 50 cm distance of the RB showed a 24.5% increase in non‐biochar soil C compared with soil at 600 cm distance of the RB, 2.54% versus 2.04%, respectively, in the non‐fertilised area, which was supported with lowering soil microbial activity. Pasture yield increase was associated with liquid BMC fertiliser rather than proximity to the RB. Pasture yield was 44% higher in the fertilised area compared with the non‐fertilised area 27.89 t ha−1 versus 19.31 t ha−1. Approximately 158 kg CO2e was removed from the atmosphere for each cubic meter of RB and an annual removal of 150 kg CO2e ha−1 was estimated by liquid BMC application. Income earned by increased yield was still profitable even though applied liquid BMC could cost between USD 400–520 ha−1 including shipping costs. Overall, our study suggested biochar‐based RB and BMC fertilisers can effectively increase soil moisture retention while building non‐biochar soil C storage in the surrounding soil. The adoption of biochar‐based techniques has the potential to improve drought resilience while increasing soil C in wide range of non‐irrigated cropping systems.