Contrasting effects of different <scp>pH</scp> ‐raising materials on <scp> N <sub>2</sub> O </scp> emissions in acidic upland soils
Yi Cheng, Huimin Zhang, Zhaoxiong Chen, Jing Wang, Zejiang Cai, Nan Sun, Shenqiang Wang, Jinbo Zhang, Scott X. Chang, Minggang Xu, Zucong Cai, Christoph Müller
Abstract
Abstract Acidic soils, occupying ca. 40% of the world's arable soils, often need to be managed (e.g., to raise their pH and to improve crop productivity); however, the environmental impact of raising soil pH is often difficult to assess. Increasing soil pH stimulates the reduction of N 2 O to N 2 , thus lowering N 2 O emissions associated with denitrification, but can also increase autotrophic nitrification rates and related N 2 O emission. Using a 15 N tracing technique, we provide process‐based insights into the effects of two acid‐neutralizing materials (quicklime [CaO] vs. pig manure) on N 2 O emissions in an acidified upland soil that had experienced excessive N application. Without pH adjustments we found that N 2 O emissions, stimulated by supply of reactive N, were related to denitrification‐ and heterotrophic nitrification‐derived N 2 O emissions, whereas autotrophic nitrification‐derived N 2 O emissions declined with decreasing soil pH. These effects were reversed by increasing soil pH via liming. However, increasing the soil pH via application of pig manure significantly increased soil N 2 O emissions from both nitrification and denitrification. Our study highlights that pH‐amelioration practices may enhance N 2 O emissions depending on the type of material applied to the soil. Therefore, both pH remediation and greenhouse gas mitigation options need to be considered together to avoid adverse environmental effects. The effect of different acid‐neutralizing materials on soil N 2 O emissions should be incorporated into ecosystem models to better estimate global N 2 O emissions when pH amelioration is practised. Highlights Enhanced N 2 O emission by N input was from denitrification and heterotrophic nitrification. Chemical N input and liming have reversible effects on N 2 O emission. Soil N 2 O emission was decreased by liming but increased by animal manure input. Careful consideration of pH raising substrates is needed to avoid adverse effects.