بررسی تأثیر بیوچار فعال‌شده و هیدروچار حاصل از جلبکChlorella vulgaris بر ویژگی‌های زیستی و آنزیمی خاک

نوع مقاله : مقاله پژوهشی

نویسندگان

• جعفر صوفیان ¹
• محمد بابااکبری ¹
• آرمن آوانس ²
• صلاح الدین مرادی ³

¹ گروه علوم خاک، دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران

² گروه شیمی، دانشکده علوم پایه، دانشگاه مراغه، آذربایجان شرقی، ایران

³ گروه کشاورزی، دانشگاه پیام نور تهران، تهران، ایران

چکیده

کلیدواژه‌ها

• اریل‌سولفاتاز
• اصلاح‌کننده خاک
• اینورتاز
• تنفس میکروبی
• میکروارگانیسم‌های خاک

موضوعات

• بیولوژی و بیوتکنولوژی خاک

عنوان مقاله [English]

The effect of activated biochar and hydrochar produced from the algae Chlorella vulgaris on the biological and enzymatic properties of the soil

نویسندگان [English]

• Jafar Sufian ¹
• mohammad babaakbari ¹
• Armen Avanes ²
• Salahedin Moradi ³

کلیدواژه‌ها [English]

• Arylsulfatase
• Invertase
• Microbial respiration
• Soil amendment
• Soil microorganisms

Introduction

 Soil microorganisms play a vital role in nutrient cycling and biochemical processes, largely relying on available carbon sources. Organic amendments like biochar and hydrochar can enhance microbial and enzymatic activity in soils. This study evaluated the effects of activated biochar and hydrochar from Chlorella vulgaris at 0.5% and 1% concentrations over 90 days, aiming to compare their effectiveness in improving microbial respiration, enzyme function, biomass carbon, and microbial populations.

Materials and Methods

 The microalga Chlorella vulgaris was cultured under controlled laboratory conditions and harvested after two weeks. The biomass was processed to produce biochar through pyrolysis at 450 °C and hydrochar via hydrothermal carbonization at 200 °C. Both biochar and hydrochar were activated using potassium hydroxide (KOH) to enhance surface characteristics. The activated materials were then mixed with soil at 0.5% and 1% concentrations. Soil incubation was conducted in a dark, controlled environment at 25 °C and 70% field capacity. Measurements included microbial respiration at set intervals, pH and microbial populations across 12 weeks, and final enzymatic assays evaluating seven key soil enzymes.

Results and Discussion

Significant shifts in soil pH were observed across treatments. Hydrochar treatments caused an initial rise in soil pH, while biochar treatments led to a gradual decline by the end of the experiment. The highest pH value of 7.82 occurred in the 1% hydrochar treatment during the first week, whereas the lowest pH of 7.53 was recorded in the 1% biochar treatment at week 12. Regarding microbial populations, both bacteria and fungi responded positively to hydrochar, particularly at higher concentrations. The bacterial population peaked at 6.33×10⁶ CFU g^-¹ dry soil in the 1% hydrochar treatment during the second week. Similarly, fungal populations reached their maximum in weeks two and three, also in hydrochar-treated soils, indicating enhanced microbial proliferation due to improved carbon and nutrient availability. All treatments exhibited an initial sharp decline in microbial respiration, which later stabilized. This rapid early drop is attributed to the consumption of readily available carbon compounds. The 0.5% hydrochar treatment showed the highest substrate-induced respiration, with a value of 858 mg CO₂ kg^-1 dry soil day^-1, significantly outperforming the control treatment, which measured only 186 mg CO₂ kg^-1 dry soil day^-1. In terms of microbial biomass carbon, the highest amount was found in the 1% hydrochar treatment at 596 mg C mic kg^-1 soil, while the control had the lowest at 213 mg C mic kg^-1 soil. These results indicate that hydrochar is particularly effective at promoting microbial growth and activity, likely due to its favorable nutrient profile and porous structure that supports microbial colonization. The study showed that both biochar and hydrochar enhanced enzyme activities in soil, with hydrochar demonstrating a stronger influence overall. Alkaline phosphatase activity was highest in the 1% hydrochar treatment, recording 2225 μg P.N.P g^-¹ soil h^-¹, while the control had the lowest activity at 1303 μg P.N.P g^-¹ soil h^-¹. Acid phosphatase activity also peaked in the hydrochar 1% treatment at 772 μg P.N.P g^-¹ soil h^-¹. Arylsulfatase activity was most elevated in the 0.5% hydrochar treatment at 286 μg P.N.P g^-¹ soil h^-¹, while the control showed only 166 μg P.N.P g^-¹ soil h^-¹. Invertase activity followed a similar trend, with the highest value recorded in the 1% hydrochar treatment at 450.5 µg glucose g^-¹ soil h^-¹. Other enzymes such as β-glucosidase, dehydrogenase, and protease also increased in activity across all treatments, with hydrochar-treated soils showing the most substantial gains. The microbial metabolic quotient (qCO₂), an indicator of microbial efficiency in carbon use, decreased with both amendments, particularly hydrochar. Lower qCO₂ values reflect more efficient microbial communities converting carbon to biomass with less energy loss. This suggests reduced soil stress and better resource availability, likely due to a shift toward more efficient groups like fungi.

Conclusion

The results of this study clearly demonstrate that activated hydrochar derived from Chlorella vulgaris outperforms biochar in improving soil biological activity. It significantly boosts microbial biomass, enzyme activity, and respiration while promoting more efficient microbial carbon utilization. These findings highlight hydrochar’s potential as an effective and sustainable soil amendment for improving soil fertility and ecological health, especially in agricultural systems seeking environmentally friendly management practices.

Author Contributions

For research articles with several authors, a short paragraph specifying their individual contributions must be provided. The following statements should be used “Conceptualization, J.S. and M.B.S.; methodology, J.S. and M.B.S.; software, A.A.; validation, J.S., M.B.S. and A.A.; formal analysis, J.S.; investigation, S.M.; resources, A.A.; data curation, S.M.; writing—original draft preparation, M.B.S.; writing—review and editing, J.S.; visualization, J.S.; supervision, J.S.; project administration, S.M.; funding acquisition, M.B.S. All authors have read and agreed to the published version of the manuscript.

All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.

Data Availability Statement

Data available on request from the authors.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The author declares no conflict of interest.