With harvest wrapping up this fall our attentions are being drawn to the next growing season already. Now’s the time to choose what seed hybrid to plant, which tillage method to implement, how much fertilizer to apply, and in some cases what source of that fertilizer to use. Controlled release fertilizers (CRF) have been on the market for some time now and have shown good results in certain situations. Before you jump in, consider how a CRFs work and whether it would be a good fit for your operation. What are the main forms? CRFs fall under a broader group of fertilizers called enhanced efficiency fertilizers (EEFs). This group includes: Controlled release fertilizers. Physical barrier such as a resin or polymer. Release affected mainly by temperature, but also by thickness of the coating, moisture, handling, and placement. Rate of release is fairly consistent. Slow release fertilizers. Microbial or chemical barrier effected by temperature, moisture, soil pH, and microbia