In a 2025 Master’s thesis titled, “Impact of nutrient-enriched biochar on soil properties and the yield formation of faba bean (Vicia faba L.),” by Dilruba Yasmin from the University of Helsinki’s Master’s Programme in Agricultural Sciences, Environmental Soil Science, the positive effects of a modified 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 are brought to light . The research, conducted at the Viikki Experimental Farm in Finland, explored how an application of organic nitrogen-loaded biochar influences the critical aspects of faba bean growth and soil health. The study specifically investigated the impact of three different biochar application rates (0, 5+15, and 10 tons/ha) combined with varying NPK fertilizer levels (30%, 65%, and 100% of the recommended dose) on a sandy clay loam soil.

One of the most critical findings relates to how the nutrient-enriched biochar impacts the soil moisture content. The data clearly showed that the application of biochar significantly improved the water-holding capacity of the topsoil layer (0−18 cm). This effect was particularly pronounced during the warmer, drier weeks of the growing season. For instance, during weeks with high temperatures and low rainfall, the plots that received the highest biochar application rate (5+15 tons/ha) maintained a moisture level clearly above the permanent wilting point (PWP). In stark contrast, the control plots, which received no biochar, consistently saw their moisture levels drop below the PWP during these stressful periods, suggesting crop development was restricted by water stress. This highlights biochar’s potential as a sustainable strategy to mitigate drought effects and enhance crop resilience in water-deficient regions

The study found that the application of nutrient-enriched biochar had a substantial positive effect on the faba bean’s vegetative growth. The maximum biochar rate (5+15 tons/ha) was a game-changer for biomass production compared to the control group (no biochar). Beyond the plant, the soil itself benefited dramatically. The nutrient-enriched biochar treatment (5+15 tons/ha) significantly increased the soil’s total carbon concentration by 32.83% compared to the control. This finding is important because biochar, with its stable aromatic structure, is highly resistant to degradation and can retain carbon in the soil for a long time, assisting in carbon storage and soil fertility.

While the biochar had a strong impact on soil moisture and carbon content, its effect on routine soil chemical properties like electrical conductivity (EC) and pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More was not statistically significant. This aligns with previous findings in the same experimental field and may be due to the already fertile and well-managed nature of the soil. Interestingly, the study found that fertilizer application rates (30%, 65%, and 100%) significantly increased concentrations of readily available phosphorus (P), potassium (K), magnesium (Mg), sulfur (S), boron (B), manganese (Mn), and zinc (Zn). However, the interaction between biochar and fertilizer was mostly minimal, suggesting that their effects operate independently for most soil properties and yield components.

It is worth noting that while biochar boosted vegetative growth, the Harvest Index (HI)—the ratio of grain yield to total biomass—did not significantly increase. This suggests that faba bean plants, though healthier and larger overall, did not necessarily reallocate a proportionally higher amount of energy toward grain production. Even so, the yield (seed) under the maximum biochar treatment was 46.51% higher than the control, although this difference was not statistically significant.

This study illuminates the potential for nutrient-enriched biochar as an effective, sustainable soil amendment, especially for boosting biomass and mitigating water stress in crops like the faba bean. Further research on how to better manage biochar application rates could help fine-tune the growth and energy allocation to maximize seed yield while retaining the clear benefits to soil health.

Source: Yasmin, D. (2025). Impact of nutrient-enriched biochar on soil properties and the yield formation of faba bean (Vicia faba L.) (Master’s thesis). University of Helsinki, Finland.