Recently, the Innovation Team for Soil Fertility Improvement and Amelioration at the Institute of Agricultural Resources and Regional Planning (IARRP), Chinese Academy of Agricultural Sciences (CAAS) revealed a dual-win mechanism by which magnesium-modified biochar enhances phosphorus availability while reducing greenhouse gas emissions in degraded red upland soils and black soils. The findings were published in Global Change Biology Bioenergy under the title "Relationship between soil phosphorus fractions and greenhouse gas emissions in degraded red and black soils amended with magnesium treated biochar."

Due to the long-term irrational application of chemical fertilizers—especially nitrogen fertilizers—red upland soils and black soils in China widely suffer from soil acidification and degradation, which in turn suppresses phosphorus activation and aggravates greenhouse gas emissions. Although biochar has been widely studied for its roles in improveing soil fertility and carbon sequestration, the mechanisms underlying its simultaneous regulation phosphorus fraction transformation and greenhouse gas emissions remain unclear, particularly for magnesium-treated biochar (Mg-BC) in enhancing phosphorus availability and mitigating greenhouse gas emissions in acidic soils.

Based on long-term field experiments conducted at the Qiyang red soil upland site of IARRP and the Harbin black soil site in Heilongjiang Province, this study investigated the effects of pristine biochar (BC) and magnesium-treated biochar (Mg-BC) on soil phosphorus fractions and greenhouse gas emissions. The results showed that both BC and Mg-BC significantly improved soil physicochemical properties, increased the labile-P pool, and decreased the moderately labile P and residual P pools, with Mg-BC showing more significant effects.

Compared with the control, both BC and Mg-BC significantly reduced N₂O emissions, with Mg-BC showing stronger mitigation effects: N₂O emissions decreased by 17%–44% in red upland soils and 16%–31% in black soils, respectively. Although biochar application increased CO₂ emissions, the increase was lower under Mg-BC treatment than under BC treatment. Structural equation modeling further indicated that biochar type and application rate had relatively small direct effects on CO₂ emissions, whereas improvements in soil pH, nutrient availability, and enzyme activities played a major role in significantly suppressing N₂O emissions (Figure 1).

This study systematically elucidates the mechanisms by which magnesium-modified biochar simultaneously enhances soil phosphorus availability and reduces N₂O emissions in degraded red upland soils and black soils, providing a solid theoretical basis for the coordinated improvement of acidic soil, enhancement nutrient availability, and mitigation of greenhouse gas emissions.

Figure 1. Pathways through which biochar regulates soil phosphorus availability and greenhouse gas emissions (upper: black soil; lower: red soil).

Muhammad Numan Khan, a Pakistani PhD graduate from IARRP (currently a postdoctoral researcher at the Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences), and Dr. Han Tianfu, Associate Professor at the School of Agriculture and Biomanufacturing, Zhengzhou University, are co-first authors. Professor Zhang Huimin, Professor Liu Wenjie, and Professor Ma Xingzhu are co-corresponding authors. The research was supported by the National Key Laboratory of Efficient Utilization of Arid and Semi-arid Arable Land in Northern China, the National Natural Science Foundation of China, and the National Key Research and Development Program of China, and other projects.

Original article: https://doi.org/10.1111/gcbb.70102