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.
