BIOCHAR | Effects of Biochar Amendment on Microbial Nutrient Limitations and Carbon Use Efficiency in Saline–Alkaline Soils: Insights Based on Ecological Enzyme C:N:P Stoichiometry
2025-06-03 17:23
Abstract
Biochar application is known to improve soil quality, enhance nutrient bioavailability, and increase carbon sequestration; however, its effects on ecological enzyme activity and stoichiometric relationships in saline–alkaline soils remain unclear. This study investigated the impacts of biochar amendment on microbial stoichiometry, nutrient limitation, and carbon use efficiency in saline–alkaline soils. Two types of biochar were compared—acid-modified biochar (pH 2.3) and alkaline biochar (pH 8.8)—applied at rates of 1%, 2%, and 5%. Results showed that alkaline biochar increased enzymatic C:N stoichiometry at higher application rates, whereas acid-modified biochar reduced C:N stoichiometry at lower rates. Both biochar types reduced enzymatic C:P and N:P stoichiometry; alkaline biochar shifted microbial metabolism from nitrogen limitation to phosphorus limitation, while acid-modified biochar alleviated nitrogen limitation at 2% and 5% application rates. Furthermore, alkaline biochar at 1% and 2% rates reduced microbial carbon limitation and improved carbon use efficiency, whereas acid-modified biochar showed no such effect. At the same application rates, microbial carbon use efficiency was consistently higher in soils amended with alkaline biochar compared to acid-modified biochar. These findings indicate that biochar’s influence on soil microbial processes depends on feedstock type, with differences in surface adsorption properties, nutrient supply, pH, and liming effects driving changes in soil properties, microbial community dynamics, and plant growth. This study provides new insights for optimizing nutrient cycling and carbon sequestration in saline–alkaline soils, demonstrating biochar’s potential for sustainable soil management.
Highlights
1.Alkaline biochar enhanced the activity of C/P-acquiring enzymes, whereas acid-modified biochar reduced the activity of N-acquiring enzymes.
2.Alkaline biochar shifted microbial nutrient limitation from nitrogen to phosphorus, while acid-modified biochar alleviated nitrogen limitation at 2% and 5% application rates.
3.Alkaline biochar at 1% and 2% application rates reduced microbial carbon limitation and increased carbon use efficiency (CUE); acid-modified biochar showed no such effect.
Conclusions
1.Although both types of biochar influenced microbial nutrient dynamics, alkaline biochar was more effective in enhancing microbial carbon use efficiency than acid-modified biochar.
2.Alkaline biochar shifted microbial nutrient metabolic limitation from nitrogen to phosphorus, whereas acid-modified biochar alleviated nitrogen limitation at higher application rates (2% and 5%).
3.Alkaline biochar, due to its higher content of active carbon and lower surface adsorption capacity, alleviated microbial carbon limitation and enhanced nutrient cycling.
4.Biochar indirectly regulated soil biochemical responses through its effects on soil properties, microbial communities, and plant traits.
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