Effects of biochar on corn yield1

ABSTRACT Biochar has been widely used as a soil conditioner to enhance the growth and yield of short-cycle crops; however, its effects on soils degraded by mining and logging remain insufficiently studied. This study aimed to evaluate the impact of seven biochar formulations on maize (Zea mays L.) yield in two localities characterized by highly degraded soils. Residues of branches, coastal slabs, leaves, and stumps were pyrolyzed and applied at doses of 1 and 2 kg m-2, in a randomized complete block factorial design. Germination, growth, biomass, and ear production were analyzed using linear mixed models. The biochar significantly increased germination, with values exceeding 79 % in all active treatments, when compared to 41.7 % in the control. Consistent increases in plant height and total dry biomass were also observed, especially in treatments derived from mixed residue formulations, which exhibited greater water-holding capacity, higher pH, and increased nutrient contents. Although stem diameter did not exhibit overall statistical differences, higher doses indicated a positive trend. Ear production increased with biochar application, although absolute yields remained below the national average, due to the severe soil degradation and high rainfall of the region. Biochar, particularly when applied in mixed formulations, has a strong potential to improve maize yield in degraded tropical soils, although its effectiveness depends on edaphoclimatic conditions and duration of soil incorporation.