Comprehensive study of biochars from different vegetative feedstocks: influence on soil properties and development of Zea mays L.

The pursuit of remediation strategies aligned with the principles of the circular economy and the Sustainable Development Goals has encouraged the use of soil organic amendments, including biochar. Biochar has the potential to enhance plant growth, improve soil fertility, and contribute to carbon sequestration. Its properties determined by the feedstock and pyrolysis conditions, and are typically characterized through proximate and ultimate analyses. However, comprehensive evaluations of biochars as soil amendments remain limited, complicating their appropriate selection for field-scale applications. The current study evaluated the properties of two commercial biochars—Ideale (IDL; derived from biomass waste) and Intermarcom (INT; derived from wood waste)—applied at 3%, 5%, and 7% rates, as influenced on soil properties and Zea mays L. growth. Soil parameters assessed included pH, total organic carbon (TOC), P2O5, NO3−, NH4+, K, Ca, electric conductivity, and permanganate oxidizable carbon. Plant performance was evaluated based on leaf area, yield, chlorophyll content, and antioxidant capacity in a pot experiment. Experimental treatments included soil-only, soil–biochar, soil–plant, and soil–biochar–plant systems to monitor biochar behavior under different conditions. Application of 3% IDL significantly promoted Z. mays growth, increasing biomass production by up to 73.2%. Higher application rates of IDL did result in further improvements. In contrast, INT negatively affected Z. mays development, reducing leaf and stem biomass by 30.7% and 49.9%, respectively. Both biochars increased soil pH and TOC but had contrasting effects on soil nitrogen dynamics. IDL incorporation led to a dose-dependent reduction in NH4+ (up to 77.3%), while NO3− levels remained largely unaffected. Conversely, INT decreased NO3− content (up to 36.6%) and increased NH4+ concentrations. Water adsorption–desorption tests confirmed the preferential adsorption of NO3-N by INT. Optimal Z. mays growth was achieved with 3% IDL, whereas INT negatively impacted plant growth at all tested application rates. These findings underscore the importance for thorough pre-application assessment of biochar properties to ensure effective and sustainable field-scale utilization.