A Controlled-Release Biofertilizer Using Composite of Poly (Urea–Formaldehyde), Date Seeds and Sulfate of Potash-Magnesia (2MgSO4·K2SO4) as All-Biodegradable With Antimicrobial Potentials

Based on the combination of poly (urea-formaldehyde) (UF), Sulfate of Potash-Magnesia (Sul-Po-Mag) fertilizer (2MgSO₄·K₂SO₄), and Date Kernel Seed (DS), a novel slow-release fertilizer in the form of granules called UF/DS/Sul-Po-Mag composite was introduced. The IR, DSC, TG, and X-ray spectra were used to characterize the synthesized composite. Characterizations revealed that the new fertilizer had good compatibility and strong hydrogen-bond interactions with improved mechanical and slow-release properties. An aqueous medium and soil incubation studies (up to 70 days) were used to examine the slow-release behavior. Over time, the accessible SO4⁻², K⁺, and Mg⁺² contents showed significantly lower SO4⁻², K⁺, and Mg⁺² losses than conventional fertilizer, even for low-polymerized materials. The fertilizer composite proved significant antimicrobial activity against all tested pathogens using the broth dilution technique. The minimum inhibition concentration (MIC) for tested bacteria and yeasts was 20 mg, while the maximum inhibition concentration (MAC) ranges from 40 to 60 mg. On the other hand, MIC for tested filamentous fungi was 100 mg, while MAC was 200–500 mg. These antimicrobial properties against harmful microbes and nutritional contents would enhance the growth of beneficial microorganisms and maintain good equilibrium in the microbial community.