Impact of biochar application on nitrous oxide and methane emissions in rainfed cropping systems within a semiarid region

Abstract

This study investigated the impact of biochar on Zea mays L. yield and greenhouse gas (GHG) emissions in rainfed maize fields in Northwest China. Four treatments were compared: unmodified control (CK), conventional nitrogen (BC0), nitrogen + 20 t ha⁻¹ biochar (BC20), and nitrogen + 50 t ha⁻¹ biochar (BC50). Results showed significant increases in grain yields with BC20 (11.1%) and BC50 (8.6%) compared to BC0. Emissions of nitrous oxide (N₂O) were reduced by 14.0%–19.5% in biochar treatments compared to CK. Methane (CH₄) uptake by the fields, acting as CH₄ sinks, was not significantly impacted by biochar treatments, clarifying that the biochar did not alter the farmland's inherent ability to uptake CH₄. Over 2 years, the addition of nitrogen fertilizer and biochar did not markedly alter cumulative CH₄ uptake. Both net greenhouse gas (NGHG) emissions and yield-scaled GHG intensity (NGHGI) were lowered by 16.7%–23.5% and 24.2%–30.3%, respectively, with biochar application. The integration of biochar effectively mitigated the GHG emission enhancement due to nitrogen fertilizer, mainly by decreasing nitrogen oxide emissions and boosting maize yields. Thus, proper biochar application would be an economical and effective strategy for mitigating gas emissions from rainfed maize cropping system in semiarid regions.