Rice cultivation is the foundation of the Cambodian food system, yet farmers increasingly face the double challenge of water scarcity and the rising environmental costs of chemical fertilizers. A new study published in the Journal of Soil Science and Plant Nutrition by Chenda Lai and a team of researchers explores a promising solution: the use of rice husk biochar combined with water-saving irrigation. By recycling agricultural waste into a soil amendmentA soil amendment is any material added to the soil to enhance its physical or chemical properties, improving its suitability for plant growth. Biochar is considered a soil amendment as it can improve soil structure, water retention, nutrient availability, and microbial activity.   More, the researchers demonstrated that farmers can achieve significantly higher productivity while protecting local water sources from pollution. The study focused on how different amounts of biochar affect the harvest and the surrounding environment when used in the most common soil types found in the region.

The researchers discovered that the amount of biochar applied makes a significant difference in the final harvest. When biochar was added at a rate of six tons per hectare alongside standard chemical fertilizers, the dry grain yield of rice increased by 40 percent in clay soils and 35 percent in sandy loam soils under water-saving irrigation. This performance outperformed both the standard fertilizer-only approach and lower rates of biochar application. Beyond just quantity, the quality of the rice also saw a notable improvement. The total protein content in the grains rose by 20 percent in the clay soil and 18 percent in the sandy loam soil. Interestingly, while the protein increased, the starch characteristics remained stable, ensuring that the nutritional boost did not negatively alter the traditional texture or cooking quality of the rice.

Environmental protection is another major benefit of this agricultural technique. Standard chemical fertilizers are prone to leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More, a process where nutrients like nitrogen and phosphorus wash out of the soil and into the groundwater, often leading to water pollution. The study found that the six-ton biochar treatment acted like a sponge, significantly reducing the loss of nitrate, ammonium, and phosphate. In sandy loam soils, which are naturally more prone to nutrient loss due to their porous structure, the biochar was particularly effective at holding onto these vital elements. By keeping nutrients in the root zone where plants can use them, the biochar not only feeds the crop more effectively but also prevents the harmful runoff that contributes to the overgrowth of algae in nearby lakes and streams.

The findings also provide good news for water management. Many farmers are adopting alternate wetting and drying techniques to save water, but there are often concerns that this can lead to lower yields compared to traditional continuous flooding. The results of this study show that biochar effectively offsets these potential losses. The porous nature of the biochar improves the soil’s ability to retain moisture and nutrients during the dry periods of the irrigation cycle. This synergy between water-saving methods and biochar application suggests a path toward a more resilient and sustainable agricultural model. By utilizing local waste products like rice husks to create biochar, Cambodian farmers can enhance their food security while significantly reducing their environmental footprint.

Source: Lai, C., Hin, S., Ket, P., Chaiwanon, J., Degré, A., & Ann, V. (2026). Combined effects of biochar and chemical fertilizers on rice yield, quality, and nutrient loss in Cambodian soils under various irrigation methods. Journal of Soil Science and Plant Nutrition.