Integrating biochar, compost, and chemical fertilizer improves maize yield and soil health in the guinea savannah: evidence from two cropping seasons in Northern Ghana

Maize production by smallholder farmers in sub-Saharan Africa is constrained by declining soil fertility due to low input use and poor nutrient management. This study evaluated the individual and combined effects of biochar, compost, and chemical fertilizer on maize growth, yield, and soil chemical properties during the 2023 and 2024 cropping seasons in Northern Ghana. A randomized complete block design was used with six treatments: control, biochar alone (B), compost alone (C), chemical fertilizer (CF), biochar + compost (½ B + ½ C), and biochar + compost + chemical fertilizer (½ B + ½ C + ½ CF). Data were analyzed using analysis of variance (ANOVA), and treatment means were separated using the least significant difference (LSD) test at a 5% probability level. The biochar + compost + chemical fertilizer (½ B + ½ C + ½ CF) treatment significantly increased maize grain yield by 105.7% in 2023 and 127.4% in 2024 compared to the control. Soil organic carbon, nitrogen, and phosphorus improved by 115.8%, 685%, and 40.2%, respectively, under this integrated treatment. The SPAD chlorophyll index, cob number, seed weight, and harvest index also increased significantly. Grain yield correlated strongly with soil pH (r = 0.88***), electrical conductivity (r = 0.94***), organic carbon (r = 0.84***), and phosphorus (r = 0.86***). The results demonstrate that integrating biochar, compost, and mineral fertilizer enhances maize productivity and soil fertility, while biochar addition contributes to increased soil carbon storage in semi-arid, low-input systems of West Africa.