Enhanced Efficiency Fertilizer Technologies
Sulfur-coated urea (SCU) fertilizers are granules of urea coated with sulfur and wax. Imperfections (cracks, fissures, fractures) in the coating allow water to move in and dissolve, then release the urea. For fertilizer particles with coatings that are intact after application, water movement through the coating results in internal osmotic pressure that cracks the coating, releasing nutrients. This process has been called catastrophic release. In addition, microbial degradation of the wax and sulfur allows water to reach the urea, dissolving and releasing it.
Polymer-coated sulfur-coated urea (PCSCU) fertilizers are an evolution of this technology. A polymer layer around the sulfur provides more protection than the wax, resulting in a longer and more predictable nutrient release.
XCU® slow-release fertilizer represents the next generation in sulfur coating technology. The order of coatings has been inverted. Urea is coated by a thin layer of polymer, then sulfur, followed by wax. The sulfur protects the ultra-thin polymer, which helps to regulate nitrogen (N) release via diffusion. The release mechanism of XCU® fertilizer is a hybrid of catastrophic release and diffusion. Because of the improved performance provided by the polymer layer, PCSCU nutrients are released more consistently over a longer time than traditional SCUs.
Reacted urea products are a type of slow-release fertilizer based on complex N compounds. These are commonly known as urea-formaldehyde (UF) and methylene urea (MU). Reacted urea is an uncoated technology that stores N in organic molecules of varying chain lengths and requires microbial activity (linked to soil temperature) for release. This slows the release of N, as only one chain link is released at a time, making it available to the plant over a longer period. Typically these products contain about 30-40% N with longevities of 8 to 26 weeks.
The reaction process during production is controlled to produce varying chain lengths. These chain lengths determine nutrient release and longevity.
Koch slow-release products include: