Descriptive of a compound manufactured in such a way that its effect will be kept uniform over an extended time period; this not only provides more effective control, but also reduces the waste involved in using unnecessarily high concentrations. This principle has been applied successfully to fertilizers, pesticides, pharmaceuticals, flavors, and fragrances. It may involve (1) encapsulation of the agent; (2) incorporating it into a neutral matrix such as a rubber or plastic; (3) coating the particles with sulfur (fertilizers); (4) absorbing the agent into substrates of various types.