In a detailed investigation published in the journal Sustainability, researchers Yassin M. Soliman, Wagdi Saber Soliman, and Ahmed M. Abbas explored the potential of integrated soil management to overcome the inherent limitations of sandy soils. These soils, which cover a significant portion of the Earth’s surface and are prevalent in Egypt’s arid regions, typically suffer from low fertility and poor water retention. To address these challenges, the team conducted a two-year field study focused on spearmint, a high-value aromatic herb. Their research examined the synergistic effects of biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More, a carbon-rich 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, alongside traditional mineral fertilizers and a natural seaweed-based biostimulant. By measuring growth traits, biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More accumulation, and essential oil production, the scientists aimed to establish a more efficient and environmentally friendly cultivation protocol.

The results of the study indicate that the application of biochar at a rate of twelve and a half tons per hectare serves as a foundational improvement for crop performance. When used alone, biochar significantly enhanced all vegetative growth parameters, including plant height and leaf area, while nearly doubling the dry weight of the harvested herb compared to untreated soil. Specifically, biochar application led to an increase in fresh weight of over fifty-eight percent and dry weight by approximately ninety-five percent in the first season. These improvements are attributed to biochar’s ability to enhance soil structure and nutrient availability, which in turn supports more vigorous plant development. The study also noted that biochar-treated plants showed higher concentrations of vital nutrients such as nitrogen, phosphorus, and potassium in their leaves.

The peak performance was achieved through a combined treatment strategy that integrated biochar with foliar sprays of nitrogen, phosphorus, and potassium fertilizer and a seaweed extract biostimulant. This specific combination produced the highest essential oil yield per plant, reaching zero point four zero three milliliters in the first season and zero point four nine zero milliliters in the second. This represents a massive improvement over plants that received no treatment at all. Furthermore, the researchers found that the concentration of photosynthetic pigments, such as chlorophyll and carotenoids, was highest in plants receiving this integrated treatment. By combining these different inputs, the study demonstrates that farmers can maximize the economic value of medicinal crops like spearmint while maintaining a focus on soil health and sustainability.

Source: Soliman, Y. M., Soliman, W. S., & Abbas, A. M. (2026). Biochar-NPK-Seaweed Integration as a Sustainable Strategy to Boost Productivity of Spearmint in Sandy Soils. Sustainability, 18(3), 1665.