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.