Biochar turns rice straw into a stronger tool for farming salty soils
A two-year field study shows that straw-derived biochar outperformed direct straw return in helping rice cope with saline-sodic stress, use nitrogen more efficiently, and produce higher yields
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Straw-derived biochar was more effective than direct straw return in mitigating soda saline-sodic stress and improving nitrogen use efficiency in rice grown in saline-sodic fields
view moreCredit: Feng Jin, Chuchu Wang, Xudong Wang, Yang Song, Qingyu Wang, Hange Liu, Hongyue Wang, Tao Wu, Wenzhu Jiang, Yu Lan, Ting Cao, Xinquan Hou, Shuang Hua & Chao Huang
Rice straw is often returned directly to fields to improve soil health, but in highly saline-sodic soils, where salt, alkalinity, and poor structure slow decomposition, that strategy may not work fast enough. A new study published in Biochar reports that converting rice straw into biochar before returning it to the field can offer a more effective route for sustainable rice production in salt-affected regions.
The study, led by Feng Jin and colleagues, compared three straw management strategies in saline-sodic paddy fields: straw removal, direct rice straw return, and rice straw-derived biochar return. The researchers also tested four nitrogen fertilizer levels, including no nitrogen, low nitrogen, a locally common nitrogen rate of 225 kg ha⁻¹, and a higher rate. The field experiment was conducted over two rice-growing seasons from 2023 to 2024 in Baicheng City, Jilin Province, China, an important region of soda saline-sodic soils.
“Our results show that biochar is not simply another form of straw return. It changes how the rice plant responds to salt stress and how efficiently it uses nitrogen,” said corresponding author Feng Jin. “For saline-sodic paddy fields, straw-derived biochar combined with moderate nitrogen input could provide a practical strategy for improving yield while making better use of fertilizer.”
Saline-sodic soils create several problems for crops. High sodium levels disrupt the balance between sodium and potassium inside plants, while salt and alkalinity can trigger oxidative stress and reduce nutrient uptake. In this study, both direct straw return and biochar helped rice plants under stress, but biochar produced stronger and more consistent improvements.
Compared with straw removal, biochar reduced sodium accumulation in rice leaves and lowered the Na⁺/K⁺ ratio, a key indicator of salt injury. At the same time, it increased potassium concentration and improved stress-related protective responses, including higher soluble protein and proline contents and stronger antioxidant enzyme activities. Biochar also reduced oxidative stress markers such as malondialdehyde, hydrogen peroxide, and superoxide anions.
The benefits extended beyond stress protection. The researchers found that straw-derived biochar enhanced nitrogen metabolism by increasing the activity of key enzymes, including nitrate reductase, glutamine synthetase, and glutamate synthase. It also upregulated genes involved in nitrogen uptake and assimilation, such as OsNR1, OsNRT1;1, OsNRT2;1, OsGS1;1, OsGS2, OsGDH2, and OsFd-GOGAT.
These physiological changes translated into measurable gains in nitrogen use and yield. Under biochar return, total nitrogen accumulation increased by 22.44% to 39.58%, and nitrogen use efficiency increased by 16.49% to 22.07% compared with straw removal. Grain yield under biochar return was 16.25% higher than straw removal and 4.04% higher than direct straw return.
The study also found that direct straw return showed delayed benefits. A significant yield difference between direct straw return and straw removal appeared only in the second year, not in the first. By contrast, biochar had a stronger overall effect across the measured plant stress, nitrogen metabolism, and yield indicators.
Using structural equation modeling, the authors identified a pathway linking biochar application to improved rice performance: biochar first alleviated physiological stress, then enhanced nitrogen metabolism, which improved nitrogen efficiency and ultimately increased grain yield.
The authors conclude that rice straw-derived biochar combined with 225 kg ha⁻¹ nitrogen was the most effective strategy tested. The findings suggest that turning straw into biochar could help farmers make better use of crop residues while improving productivity in saline-sodic paddy fields.
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Journal Reference: Jin, F., Wang, C., Wang, X. et al. Straw-derived biochar was more effective than direct straw return in mitigating soda saline-sodic stress and improving nitrogen use efficiency in rice grown in saline-sodic fields. Biochar 8, 125 (2026).
https://doi.org/10.1007/s42773-026-00619-7
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
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Journal
Biochar
Method of Research
Experimental study
Article Title
Straw-derived biochar was more effective than direct straw return in mitigating soda saline-sodic stress and improving nitrogen use efficiency in rice grown in saline-sodic fields
Article Publication Date
6-Jul-2026
Waste cotton stalks and eggshells transformed into reusable biochar for antibiotic removal from wastewater
A new study reports a microwave-assisted biochar adsorbent that removes tetracycline from water while combining experimental chemistry, machine learning, quantum calculations, and life cycle assessment
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Microwave-assisted β-cyclodextrin modified calcium-rich biochar for tetracycline removal from wastewater: mechanistic, machine learning, density functional theory calculations and life cycle assessment
view moreCredit: Chong Liu, Grégorio Crini, Ricardo Bello-Mendoza, Lee D. Wilson, Ali H. Jawad, Paramasivan Balasubramanian, Xuan Cuong Nguyen, Qingfu Zheng & Fayong Li
Antibiotic residues in water are an increasing environmental concern, especially as widely used medicines can pass through human, livestock, and aquaculture systems and enter rivers, groundwater, and soils. Tetracycline, a common broad-spectrum antibiotic, is one such pollutant. Although effective for treating bacterial infections, it can persist in the environment and contribute to ecological risks.
Now, researchers have developed a promising material that turns two abundant wastes, cotton stalks and discarded eggshells, into a high-performance adsorbent for removing tetracycline from contaminated water. The study, published in Biochar, presents a β-cyclodextrin modified calcium-rich cotton-stalk biochar, named Ca@CBC/β-CD, prepared through a microwave-assisted crosslinking process.
“Our goal was to design a practical adsorbent that is not only efficient, but also built from low-cost and waste-derived resources,” said corresponding author Prof. Fayong Li. “By combining cotton-stalk biochar, eggshell-derived calcium, and β-cyclodextrin, we created multiple ways for the material to capture tetracycline molecules.”
The new material works through a combination of physical and chemical interactions. The cotton-stalk biochar provides a porous carbon framework. Eggshell-derived calcium introduces active mineral sites. β-cyclodextrin, a ring-shaped molecule produced from starch, adds cavity-like structures and hydroxyl groups that can help trap organic pollutants.
In laboratory tests, Ca@CBC/β-CD showed its best tetracycline adsorption near pH 6, a condition relevant to many natural and wastewater systems. Its maximum adsorption capacity reached 161.91 mg g⁻¹ at 45 °C, higher than the capacity measured at lower temperature. The material also showed good resistance to common coexisting ions in water and maintained about 84 to 86% of its initial adsorption capacity after five reuse cycles, suggesting potential for repeated operation.
To understand why the adsorbent performed well, the team used spectroscopic analyses and density functional theory calculations. The results showed that tetracycline removal was driven by calcium-mediated inner-sphere complexation and surface bridging, β-cyclodextrin host-guest inclusion, and multi-point hydrogen bonding. In simpler terms, tetracycline molecules are not captured by just one mechanism. They are held by several cooperative interactions across the biochar surface.
The study also incorporated machine learning to predict adsorption behavior under different experimental conditions. Among six tested models, the gradient boosting decision tree model performed best, achieving a test-set R² of 0.9914. The model identified initial tetracycline concentration, adsorbent dosage, and contact time as the most important factors controlling adsorption capacity. The researchers also developed a Python-based graphical interface for rapid prediction and experimental design.
“Machine learning helped us move beyond single-factor experiments,” said co-author Prof. Grégorio Crini. “It provides a faster way to estimate performance and can guide future optimization before costly experiments are performed.”
The researchers further evaluated the environmental footprint of producing the adsorbent. A life cycle assessment found that the preparation stage generated 5.44 kg CO₂-equivalent per kg of adsorbent, with electricity use as the main environmental hotspot. This points to a clear improvement pathway: reducing energy demand during production could make the material more sustainable.
The authors note that the work is a proof of concept and that future studies should optimize the eggshell-to-biochar ratio, β-cyclodextrin dosage, microwave conditions, and test the material in continuous-flow systems.
Together, the findings offer a waste-to-resource strategy for antibiotic pollution control and provide a design framework for developing next-generation biochar adsorbents for real-world wastewater treatment.
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Journal Reference: Liu, C., Crini, G., Bello-Mendoza, R. et al. Microwave-assisted β-cyclodextrin modified calcium-rich biochar for tetracycline removal from wastewater: mechanistic, machine learning, density functional theory calculations and life cycle assessment. Biochar 8, 124 (2026).
https://doi.org/10.1007/s42773-026-00640-w
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
Follow us on Facebook, X, and Bluesky.
Journal
Biochar
Method of Research
Experimental study
Article Title
Microwave-assisted β-cyclodextrin modified calcium-rich biochar for tetracycline removal from wastewater: mechanistic, machine learning, density functional theory calculations and life cycle assessment
Article Publication Date
2-Jul-2026
Green manure and biochar help farmers cut nitrogen use while rebuilding soil health
A multi-year field study shows that pairing legume green manure with biochar can improve soil quality, support maize yield, and reduce dependence on nitrogen fertilizer
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Synergistic effects of green manure and biochar for a win-win in nitrogen reduction and soil health: insights from multiple assessment frameworks
view moreCredit: Lianhao Zhao, Xinjian Zhang, Xiaoguang Ning, Wen Yin, Qiu Zhao, Pan Li, Feier Wang, Hailong Qiu, Zhilong Fan, Falong Hu, Qiang Chai, Heyu Chen, Mohamed Abdalla, Saeed Karbin & Pete Smith
A new study published in Biochar shows that combining green manure with biochar can help farmers reduce nitrogen fertilizer use while improving soil health, water retention, carbon storage, nutrient supply, and microbial activity.
The research, titled “Synergistic effects of green manure and biochar for a win-win in nitrogen reduction and soil health: insights from multiple assessment frameworks,” was conducted by Lianhao Zhao and colleagues through a three-period field experiment from 2021 to 2024 in a maize cropping system on the North China Plain. The team tested winter fallow, green manure, and green manure plus biochar under conventional fertilization and different levels of controlled-release fertilizer reduction.
Modern crop production has often relied on heavy fertilizer inputs to secure yields, but excessive nitrogen use can worsen soil acidification, disrupt nutrient balance, reduce biological activity, and increase environmental losses. The new study points to a more balanced path: moderate nitrogen reduction combined with organic field practices that restore the soil’s natural functions.
“Our results show that nitrogen reduction does not have to come at the cost of soil health or crop productivity,” said corresponding author Wen Yin. “When green manure and biochar were used together, they created a stronger and more resilient soil system, especially under moderate controlled-release fertilizer reduction.”
The strongest performance was found when green manure and biochar were combined under a 30% reduction in controlled-release fertilizer. Under this treatment, the soil showed the greatest improvements in water retention, carbon sequestration, nitrogen fixation, nutrient supply, microbial diversity, and overall soil quality. The study also found that maize yield could be maintained under this moderate fertilizer reduction, while nitrogen fertilizer productivity increased.
In contrast, a 45% fertilizer reduction created risks of excessive nitrogen cutback, lowering key nutrient functions and reducing yield. This finding suggests that fertilizer reduction should be carefully calibrated rather than applied as a simple across-the-board cut.
A key innovation of the study was its use of multiple soil quality assessment frameworks. The researchers measured 22 soil indicators, including physical, chemical, and biological properties, and built a soil function-based evaluation system covering five core functions: water retention, carbon sequestration, nitrogen fixation, nutrient supply, and microbial diversity provision. They also compared this approach with two minimum dataset methods based on principal component analysis and network analysis.
The soil function-based framework provided the highest accuracy, while the principal component-based minimum dataset offered the best balance between efficiency and accuracy. The network-based method maintained reasonable accuracy using only four indicators, making it promising for rapid screening across larger areas.
One of the most important findings was that soil microbial diversity emerged as a central driver of improved soil quality. Green manure and biochar appeared to work mainly by strengthening microbial diversity and water retention, which then indirectly supported carbon sequestration and nutrient supply.
“Healthy soil is not only about adding nutrients,” said corresponding author Qiu Zhao. “It is about restoring the biological and physical processes that allow soil to store water, cycle nutrients, protect carbon, and support stable crop production.”
The study provides a practical framework for designing sustainable maize systems in the North China Plain and similar agricultural regions. By integrating green manure, biochar, and moderate controlled-release fertilizer reduction, farmers may be able to reduce fertilizer inputs, maintain yield, and rebuild degraded soils at the same time.
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Journal Reference: Zhao, L., Zhang, X., Ning, X. et al. Synergistic effects of green manure and biochar for a win-win in nitrogen reduction and soil health: insights from multiple assessment frameworks. Biochar 8, 123 (2026).
https://doi.org/10.1007/s42773-026-00638-4
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
Follow us on Facebook, X, and Bluesky.
Journal
Biochar
Method of Research
Experimental study
Article Title
Synergistic effects of green manure and biochar for a win-win in nitrogen reduction and soil health: insights from multiple assessment frameworks
Article Publication Date
2-Jul-2026
