Farmland soil is an important source of greenhouse gas emissions, accounting for about 10-12 percent of the total greenhouse gas. It has been a significant strategy for different countries around the world to mitigate greenhouse gas emissions from farmland to ensure food security and cope with global warming. Red soil is the main arable land resource in the hilly areas of southern China; however, various reasons such as soil properties and unreasonable development by humans have resulted in poor soil fertility in the area, particularly in serious magnesium (Mg) deficiency and acidification, which in turn affects greenhouse gases emissions. Biochar is often used as a conditioner to improve soil quality and reduce greenhouse gas emissions from farmland, but the impact of biochar, especially when magnesium-modified, on greenhouse gas emissions during the red soil improvement process is still unclear.

In this study, a long-term fertilization test at the Red Soil Experimental Station of the Chinese Academy of Agricultural Sciences in Qiyang, Hunan Province, pristine wheat straw biochar (WBC) and magnesium modified wheat straw biochar (MWBC) were used to conduct a red soil improvement experiment and study the impact of WBC and MWBC on soil physiochemical properties, urease and phosphatase activities, and microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), as well as on greenhouse gas emissions (CO₂, CH₄ and N₂O). The research found that soil physiochemical properties improved, urease and phosphatase activity increased while dehydrogenase and β-glucosidase activities decreased with the WBC and MWBC application. MWBC2.5 significantly decreased microbial biomass carbon (MBC), while microbial biomass nitrogen (MBN) increased when both biochar materials (WBC1 and MWBC1) were applied at low rates. WBC and MWBC increased cumulative emissions of CO2, but decreased N2O cumulative emissions (Figure 1). Compared to WBC, MWBC decreased cumulative emissions of CO₂ and N₂O. These findings indicate that Mg-modified wheat straw biochar would be an appropriate strategy to reduce greenhouse gas emissions and improve the physiochemical properties of affected soils, especially red dry land soil. The research results are of great significance for guiding red soil fertilization, nutrient management, and carbon sequestration and emission reduction.

Titled “Mitigation of greenhouse gas emissions from a red acidic soil by using magnesium-modified wheat straw biochar”, the research results were published in the journal Environmental Research (2020 Impact Factor: 6.498). Muhammad Numan Khan, a Pakistani doctoral student from the Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, is the first author, and Zhang Huimin, research fellow and doctoral supervisor at the Qiyang Red Soil Experimental Station of the Chinese Academy of Agricultural Sciences, is the corresponding author. The research was funded by a few programs including the National Key Research and Development Program of China and a central-level public welfare project.

Figure 1: Emissions of CO₂, CH₄ and N₂O (L) of different treatments and cumulative emissions (R)

Note: CK is control treatment; WBC₁ and WBC_2.5 are WBC with biochar materials at 1% and 2.5%. MWBC₁和MWBC_2.5 are WBC with biochar doses at 1% and 2.5%.

https://www.sciencedirect.com/science/article/pii/S0013935121011749?dgcid=author