Controlled‐release fertilizer is one of the most critical tools in agribusiness for decreasing environmental impacts. Thus, the development of bio‐based systems able to induce the slow release of fertilizers has become the focus of numerous researchers. In this sense, this work presents a slow‐release fertilizer prepared by melt mixing of poly(butylene succinate) filled with 30 wt % urea and 5 wt % montmorillonite clay. The obtained materials were characterized using FTIR, XRD, and SAXS. Also, the release of urea was investigated using gravimetric and spectrophotometric tests. Finally, a vegetable growth analysis was performed to evaluate the development of lettuce (Lactuca sativa L.). The best composite material can increase the diameter of the lettuce by 67%, whereas the conventional use of urea increased this diameter by 48%. Therefore, the presented materials are useful as fertilizer systems.