A scanning electron microscope study of pressure- and airsprayed sulfur coatings, applied to control the release rate of urea as a nitrogen fertilizer, shouts that the coatings are mixtures of orthorhombic and polymeric sulfur. The observed sulfur textures vary with the thermal history of the coatings and can be correlated with the performance of the product as a controlled-release nitrogen fertilizer. The satisfactory performance of some sulfur coatings and the unsatisfactory performance of others are related to the presence of desirable sulfur textures and the absence of controllable defects. The principal mechanism of controlled nitrogen release is through pores in the coatings. Sealants can minimize the effects of coating defect