In the journal RSC Advances, researchers Manman Yuan, Jiabao Wang, Gang Wu, Pingping Wu, Chengshun Wang, Chuang Liu, Qi Miao, and Yixiang Sun conducted a comprehensive meta-analysis evaluating how biochar application influences crop secondary- and micro-nutrient acquisition. Deficiencies in essential secondary nutrients and micronutrientsThese are essential nutrients that plants need in small amounts, kind of like vitamins for humans. They include things like iron, zinc, and copper. Biochar can help hold onto these micronutrients in the soil, making them more available to plants.   More present global challenges for agricultural yield, crop health, and human dietary nutrition. While biochar has gained traction as a sustainable 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 capable of modifying nutrient dynamics, previous individual studies yielded highly variable findings depending on environmental conditions and biochar properties. To resolve these inconsistencies, the authors analyzed 144 paired observations from peer-reviewed field and pot experiments spanning seven key elements: calcium, magnesium, sulfur, iron, manganese, copper, and zinc.

The synthesized results demonstrate that biochar application significantly increases crop aboveground biomass by an average of 30.8%. This substantial expansion in plant biomass drives a 12.8% increase in total secondary- and micro-nutrient accumulation across crops, even though overall combined nutrient concentrations remain statistically unchanged. Vegetables displayed the strongest positive response to biochar amendment, exhibiting a 42.1% increase in aboveground biomass alongside enhanced element accumulation. Cereals and other cash crops also demonstrated consistent, albeit moderately lower, positive increases in biomass and total nutrient uptake.

Despite the stability of total overall nutrient concentrations, the meta-analysis uncovered distinct element-specific regulatory patterns. Biochar application significantly increased tissue concentrations of iron by 13.3%, copper by 20.3%, and zinc by 9.6%. Conversely, biochar amendment reduced plant concentrations of magnesium by 8.3%, manganese by 15.5%, and sulfur by 4.7%, while leaving calcium concentrations essentially unaffected. These element-specific shifts stem from biochar-induced changes in soil 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 and chemical speciation, which alter nutrient bioavailability, complexation, and root uptake pathways.

The intrinsic properties of biochar proved to be the dominant regulators determining the magnitude of nutrient acquisition. Biochar produced at medium pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More temperatures between 400°C and 500°C yielded optimal structural porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More and surface functional groups, driving the highest overall nutrient concentration and accumulation improvements. Wood-derived biochars outperformed straw, herb, and manure or sludge feedstocks. Furthermore, lower application rates of 1% or less by weight and alkaline biochar pH provided the strongest benefits, whereas higher application rates above 3% tended to excessively raise soil pH and restrict nutrient availability.

The regulatory trends remained highly consistent across varying external environmental conditions. Subgroup analyses revealed that soil texture classes, soil pH levels, and experimental testing methods did not alter the fundamental response directions of nutrient concentration or accumulation. The authors concluded that biochar acts as a reliable regulator of crop secondary- and micro-nutrient status, offering actionable parameters for sustainable agricultural management.

Source: Yuan, M., Wang, J., Wu, G., Wu, P., Wang, C., Liu, C., Miao, Q., & Sun, Y. (2026). Biochar-mediated uptake of secondary- and micro-nutrients in crops: a meta-analysis. RSC Advances, 16, DOI: 10.1039/d6ra03366k.