<p>Agronomic benefits of applying biochar into soils, as a sustainable and environment-friendly soil amendment approach, have been well-documented for decades, known for improving soil water and nutrient retention capacity followed by better crop production. Still, research on the effects of certain locally sourced biochar waste and combined use with fertilizer and compost on agricultural lands with sandy soils is rather limited. Therefore, our study attempted to explore the effects of locally produced biochar waste amended with compost and fertilizer on the water retention, pH, and nutrients of the sandy wild blueberry soil in Maine. We found that the studied biochar (either mixed with compost or fertilizer) effectively improved the water holding capacity (WHC) of the sandy wild blueberry field soil, with 15% and 20% application (biochar mix % in soil by weight) showing the highest effect. On the other hand, the studied alkaline biochar caused a significant increase in the soil pH up to 7–8, which would not be favorable for wild blueberry plants naturally growing in acidic soil (pH: 4–5). While our study also attempted to lower the soil pH by treating the studied alkaline biochar with mild acid, it did not lower the soil pH below 7. Our study further revealed that the 50–50 ratio for the biochar-compost/fertilizer mix application could be the most beneficial for the wild blueberry soil. This ratio could enhance WHC significantly while providing the most useful nutrient elements (P, K, Ca, B) for the wild blueberry plants, and keeping the heavy metals (Al, Fe) in check.</p> Graphical Abstract <p></p>