Biochar: caracterização, efeito na fertilidade do solo e no crescimento inicial de milho

Abstract

Biochar, obtained through the controlled pyrolysis of plant biomass, has been identified as a promising input for improving the fertility of tropical soils and increasing nutrient- use efficiency, integrating strategies for sustainable, low-carbon, and circular agriculture. The aim of this study was to characterize biochar produced from corn processing residues, denominate biomix and to evaluate its effects on soil chemical attributes and the initial growth of maize (Zea mays L.), including physiological, nutritional, and efficiency parameters. The biochar was produced at 500 °C and characterized for solid composition, SEM-EDS, and thermogravimetric analysis (TGA), presenting an alkaline pH, intermediate ash content, high thermal stability, and a heterogeneous structure with mineral fractions mainly concentrated in potassium (K)—attributes compatible with agricultural lignocellulosic biochars and consistent with the literature.The experiment was conducted in eutroferric Red Latosol (Oxisol) cultivated in pots, using a completely randomized design with six biochar doses (0, 5, 10, 20, 40, and 80 t ha⁻¹). Biochar application increased soil pH, the sum of bases, base saturation, and cation exchange capacity, in addition to markedly increasing phosphorus (P) and potassium (K) availability, evidencing improvements in soil chemical fertility and aligning with expected behavior for acidic and highly weathered tropical soils. Physiological responses indicated an increase in root dry matter, while chlorophyll contents remained stable, suggesting adequate nitrogen (N) supply in the system and reinforcing that initial gains were more pronounced in the root compartment. Mineral nutrition exhibited contrasting patterns among macronutrients, with increases in foliar P and K and no significant response for nitrogen, a pattern coherent with urea fertilization and the low dependence of N on edaphic processes in the short term. Nutrient use efficiency (NUE) and nutritional sufficiency indices (NSI) reinforced that biochar acted predominantly on P and K, enhancing both physiological efficiency and foliar sufficiency, especially at intermediate doses (20–40 t ha⁻¹), suggesting that these doses promoted a better balance between soil availability, plant uptake, and biomass conversion. In summary, the Biomix used in this study acted as a soil chemical conditioner and modulator of nutritional dynamics, with higher response potential for nutrients strongly influenced by edaphic processes, while nitrogen proved to be more dependent on fertilizer management. The results highlight the agronomic potential of biochar in tropical soils and its suitability for low-carbon agriculture, bioeconomy, and circular economy pathways, contributing unprecedented evidence on the use of biochar from corn processing residues and expanding the understanding of its modes of action and potential as a bioeconomic input.