Biochar has been heralded for improving soil quality, sequestering C, and converting organic residues into value-added amendments. Biochar research in agricultural settings has been primarily conducted on acidic soils, with few studies evaluating biochar effects on alkaline soils. Given the rise of small-scale, sustainable farmers experimenting with biochar in South Florida's alkaline, carbonaceous soil, this study sought to assess biochar use in South Florida using an invasive plant species as a feedstock. (Cav.) S.T. Blake biomass was converted into biochar to measure how application at two rates, 2 and 5% (w/w), affects plant growth, soil macro- and micronutrients, and microbial gas flux (CO) in a potted greenhouse experiment using L. Plant growth was inhibited with biochar addition at the 2 and 5% rates. Dry shoot, pod weight, and pod length decreased significantly between treatments ( < 0.001). Significant reductions in plant-available P, Ca, Mg, Cu, and Zn were observed in the 5% biochar soil postharvest ( < 0.05). Compared with the control, addition of biochar at 2 and 5% rates significantly reduced CO flux during the growing season, but not at harvest ( < 0.01). Our results indicate that those considering biochar application in South Florida's alkaline soil should be cautious in selecting feedstock and temperature for biochar production. Biochar can be produced at lower temperatures to decrease pH, but the concomitant increase in volatile matter (VM) is of concern. Although CO flux may have decreased, the deleterious impacts of biochar (pH = 8.12, VM = 26.5%) on production should not be dismissed.
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