<p>Crop production in tropical soils is often constrained by inherent infertility, acidification, and phosphorus sorption, challenges that can be addressed with empty oil palm fruit bunch (EFB) biochar. However, its use in small-scale farming in Ghana is relatively new, and there is limited information on safe application rates for different soils. This study aimed to determine the optimal loading capacity of EFB biochar for various tropical soils, focusing on immediate chemical responses, potential phytotoxicity and nutrient uptake across different application rates. The study examined the effect of EFB biochar application on soil chemical properties, maize phytotoxicity and nutrient uptake in four tropical soils (Acrisol, Brown and Red Ferralsols and Vertisol) in incubation, germination and pot experiments. EFB biochar application increased the pH of all the soil types except Vertisol. At a 2% w/w application rate, available phosphorus increased by 175%, 68.9%, and 49%, and total organic carbon contents also increased by 49%, 22%, and 19% in Acrisol, Brown Ferralsol and Vertisol, respectively. The study observed no phytotoxic effect of EFB biochar on maize germination in all soil types. Additionally, the co-application of EFB biochar with inorganic fertiliser significantly increased N and P uptakes in the Acrisol, but the positive effect was insignificant for the other soil types. Based on the comprehensive amelioration score, the highest application rate of 2% emerged as the ideal rate for Acrisol, Red Ferralsol and Vertisol soil types, whilst a rate of 1% was best suited for the Brown Ferralsol. The findings suggest that EFB biochar has the potential to resolve problems of acidification and phosphorus sorption and can also enhance nutrient uptake in certain tropical soils, without having phytotoxic effects on germination. However, the magnitude of these effects varied with soil types and was more pronounced in the Acrisol.</p>