Purpose <p>Low soil fertility is the main challenge in crop productivity in calcareous soils. This study investigated the influence of biochars derived from maize straw and sugarcane bagasse and their acidified forms, on soil fertility status and maize (<i>Zea mays</i> L.) growth parameter in calcareous soil.</p> Methods <p>A pot experiment on maize cultivation was conducted. Conditions included control (C), sugarcane bagasse (SB), maize straw (stalk and leaves) (CR), acidified sugarcane bagasse (ASB), and sulfur acidified maize straw (ACR) treatments, at 1% (w/w).</p> Results <p>The results showed that the application of sulfur treated biochar decreased soil pH by 0.40–0.49 units. Simultaneously, it significantly increased the cation exchange capacity (CEC) (11.0–15.8%), soil organic carbon (OC), (96.5–217.6%), dissolved organic carbon (DOC) (44.6–72.5%) compared to control treatment. In addition, biochar application increased soil available N, P, K, Fe, Zn, Mn, and Cu concentration compared to control treatments, which varied based on the feedstock and biochar type. The results revealed that the acidified maize straw biochar was more effective in improving the soil fertility status and maize growth parameters compared to other biochars. CR and ACR application increased the shoot dry matter by 50.9 and 64.8% and root dry matter by 53.2 and 78.6%, respectively, compared to unamended soil. The results also revealed that acidifying biochar increased its efficiency in improving soil attributes and maize growth.</p> Conclusions <p>The findings demonstrated that maize biochar and its acidified biochar can be used as a suitable amendment for improving soil fertility and maize growth in calcareous soils.</p>