The Effect of Cereal Crop Type on Reducing Emission Intensity With Biochar Application in Monsoon Asia

Biochar amendments can reduce greenhouse gas (GHG) emissions from agricultural soils while helping to maintain food security. However, whether the effect of biochar application on emission intensity (EI) of non-CO₂ greenhouse gas emissions (including methane (CH₄) and nitrous oxide (N₂O)), per unit of crop caloric content, varies for different crops and its driving mechanism remains unclear. Here, we conducted a meta-analysis of EI changes (ΔEI) with biochar application for three major cereal crops: rice, wheat, and maize, based on 202 observations from 41 research publications from Monsoon Asia. Our results showed that biochar application reduced the EI for all three crops by an average of −14.6 kg CO₂ eq M cal⁻¹, with the greatest reduction in ΔEI for rice (−28.9 kg CO₂ equation M cal⁻¹). Biochar application-induced reduction in CH₄ emissions (−0.4 Mg CO₂ eq ha⁻¹) was the main contributor to ΔEI for rice, which was greater than those for upland crops: maize and wheat (−0.1 Mg CO₂ eq ha⁻¹ and 0.3 Mg CO₂ eq ha⁻¹, respectively). Crop type directly affected ΔEI after biochar application. Additionally, crop type indirectly influenced ΔEI by associating with soil organic carbon and clay contents for N₂O emission and CH₄ emission, respectively. This study highlights that biochar application to soil reduces EI across the globally important agricultural region, and these reductions were most pronounced for rice compared to wheat and maize. Our study provides a better understanding of the effects of biochar on GHG emissions for three important crops and can facilitate the development of new strategies for agricultural GHG mitigation while maintaining food security for the future.