Influence of biochar doses and application methods on soil fertility and bean productivity

The conversion of agro-industrial waste into biochar can reduce pollution and sequester carbon in the soil, contributing to climate change mitigation. In agriculture, its use improves the chemical, physical, and biological properties of the soil. Although extensively studied, the effects of low doses and application methods on grain yield are still underexplored in real field conditions. This study evaluated the most efficient dose and application method of biochar in the production of beans (Phaseolus vulgaris L.). The experiment followed a randomized block design with a factorial scheme of 4 × 2 + 2, testing four doses (600, 900, 1,200, and 1,800 kg ha⁻¹), two application methods (surface and incorporated), and two controls (fertilized and unfertilized). The biochar, produced by NetZero via pyrolysis of coffee husks (Coffea arabica L.), was applied at planting. Soil samples were collected before and after cultivation for chemical analysis. Yield was estimated after harvest, standardizing the moisture content of the grains. Data were analyzed in R Studio using analysis of variance and mean comparison tests (Scott-Knott and Dunnett, p ≤ 0.05). The application of biochar increased grain yield and improved K, Ca, CEC, and V% levels compared to the fertilized control. The average increases were 96% for yield (539 vs. 275 kg ha⁻¹), 13.2% for K (256 vs. 226 mg dm⁻³), 7.8% for Ca (2.48 vs. 2.30 cmolc dm⁻³), 9.5% for CEC (4.3 vs. 3.9 cmolc dm⁻³), and 13.3% for V% (52.8% vs. 46.6%). The dose of 900 kg ha⁻¹ incorporated resulted in a yield three times greater than surface application (326 vs. 919 kg ha⁻¹). However, high variability in yield was observed, along with a relatively low yield in the winter crop. To deepen the understanding of the effects, more growing cycles will be evaluated. The results indicate that biochar in low doses improves soil fertility and productivity, as well as contributes to the Sustainable Development Goals (SDGs) by promoting climate change mitigation and encouraging a more sustainable agricultural model through carbon sequestration and the utilization of agro-industrial waste.