In a study published in the journal Biochar, lead author Feng Jin and a team of researchers examined alternative straw management strategies to help farmers overcome the severe agricultural constraints of highly saline-sodic soils. In regions like the Songnen Plain in Northeast China, extreme soil salinity and alkalinity drastically lower agricultural productivity, leaving conventional rice paddies with exceptionally poor fertilizer efficiency. Traditionally, returning raw crop straw directly to fields has been used to maintain soil health, but the hostile, high-salt conditions of sodic soils inhibit natural decomposition, heavily delaying any nutritional benefits. To resolve this dilemma, the authors evaluated whether transforming rice straw into a porous, stable biochar could offer a superior pathway for safeguarding crop physiology, maximizing nitrogen fertilizer consumption, and boosting food production.

The field study yielded striking results, demonstrating that returning straw-derived biochar to saline-sodic paddy fields consistently outperformed both direct straw return and conventional straw removal. Over the experimental period, fields treated with biochar achieved a significant 16.25% increase in rice grain yield compared to the control plots where straw was entirely discarded. Furthermore, biochar provided a 4.04% yield advantage over direct straw application. Interestingly, while raw straw return did eventually improve grain production, its positive impacts were completely absent during the first year of application because the tough organic material failed to decompose in the harsh saline environment. In contrast, the biochar amendment provided immediate structural and chemical benefits, resulting in reliable yield enhancements right from the very first harvest season.

The primary driver behind this agricultural success was biochar’s superior capacity to alleviate severe ionic toxicity and oxidative stress within the rice plants. Saline-sodic soils normally force a massive, toxic influx of sodium into plant tissues, which damages cellular membranes and blocks vital nutrient absorption. The researchers discovered that the biochar matrix acted as a highly efficient chemical sponge, utilizing its vast internal surface area and high cation exchange capacity to physically trap toxic sodium ions directly in the soil. As a result, the toxic accumulation of sodium inside the rice leaves dropped by up to 17.13%. Simultaneously, the biochar rapidly released essential potassium into the soil solution, increasing leaf potassium concentrations by 15.73% and allowing the plants to maintain a healthy internal ionic balance. This restored equilibrium stimulated the plants’ natural antioxidant defense systems, dramatically reducing internal stress markers like hydrogen peroxide and preventing cellular deterioration.

With the physical salt stress mitigated, the rice crops exhibited a profound metabolic upgrade, allowing them to absorb and assimilate nitrogen fertilizer with unprecedented efficiency. Sodic stress typically cripples a plant’s internal nitrogen machinery, but the biochar application significantly upregulated key metabolic genes and amplified the performance of critical plant enzymes, such as nitrate reductase and glutamine synthetase. This metabolic boost enhanced total nitrogen accumulation within the crops by 22.44% to 39.58% compared to untreated plots. Ultimately, net nitrogen use efficiency surged by 16.49% to 22.07% under the biochar treatment. Structural equation modeling confirmed that this entire process operated as a beautifully synchronized causal chain, where the initial relief from salt toxicity directly unlocked superior nitrogen metabolism, which subsequently optimized fertilizer transport and maximized final grain weight and panicle numbers. The team concluded that blending straw-derived biochar with a moderate nitrogen fertilizer rate of 225 kilograms per hectare creates the absolute ideal management blueprint for sustainably reclaiming vulnerable saline wetlands.

Source: Jin, F., Wang, C., Wang, X., Song, Y., Wang, Q., Liu, H., Wang, H., Wu, T., Jiang, W., Lan, Y., Cao, T., Hou, X., Hua, S., & Huang, C. (2026). 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), 1-29.