AbstractA new controlled release fertilizer was developed by coating urea particles with bio-based polyurethane. Coating materials were synthesized from liquefied wheat straw, isocyanate, and castor oil. The effects of liquefied solvents, mass ratio of liquid to solid, size of wheat straw, and reaction time during liquefaction process on the nitrogen release rate of polyurethane-coated urea (PCU) were investigated and optimized. The nitrogen release characteristics of PCU were studied in both water and soil. The structural and chemical characteristics of PCU were examined. The PCU coating materials showed high density and good degradability, as well as superior controlled release properties. This product, with excellent controlled release properties, nontoxicity in soil, environmental friendliness, and low cost, could be especially useful in agricultural and horticultural applications.