This is the fifth in a series on slow release fertilizers for turf and landscapes. This post contains information on ureaformaldehyde reaction products.
Ureaformaldehyde Reaction Products, also known as Nitroform, Ureaform, UF, Methylene Urea, Blue Chip, Nutralene or Methex, represent one of the oldest controlled-release nitrogen technologies, having been first produced in 1936 and commercialized in 1955.
Ureaform is the oldest class of UF reaction products. Ureaform is sparingly soluble. It contains at least 35% total nitrogen with at least 60% of the total nitrogen as cold water-insoluble nitrogen (CWIN). Further, it must have an Activity Index (AI), i.e., the percent of CWIN that is soluble in hot (100°C) water, of not less than 40%. Ureaform is composed largely of longer-chained UF polymers, primarily tetramethylene pentaurea (TMPU) and longer. Unreacted urea nitrogen content is usually less than 15% of the total nitrogen. This product is commonly marketed under the following names: Nitroform, UF, Blue Chip, Powder Blue or Methex.
Methylene Ureas are a class of sparingly soluble products which evolved during the 1960s and 1970s. These products contain predominantly intermediate chain-length polymers, primarily trimethylene tetraurea (TMTU) and tetramethylene pentaurea (TMPU). The total nitrogen content of these polymers is 39 to 40%, with between 25 and 60% of the nitrogen present as CWIN. The unreacted urea content generally is in the range of 15 to 30% of the total nitrogen. This product is typically marketed under the trade name Nutralene.
UF solutions are clear water solutions. They contain only very low molecular-weight, water soluble UF reaction products plus unreacted urea. Various combinations of the UF solutions are produced. They contain a maximum of 55% unreacted urea with the remainder as one or more of methylolureas, methylolurea ethers, MDU, DMTU, or triazone. One of the commercial names under which this product is currently marketed as CoRon.
Agronomic Properties and Nutrient Release Mechanism of UF Products:
The conversion of UF reaction products to plant available N is a multistep process, involving dissolution and microbial decompositon. Once in the soil solution, UF reaction products are converted to plant available N through either microbial decomposition or hydrolysis. Microbial decomposition is the primary mechanism of N release with the carbon in the methylene urea polymers providing the site for microbial activity. Environmental factors such as soil temperature, moisture, pH and aeration affect the rate of N release.
The rate of N release from UF reaction products is directly affected by polymer chain length. The longer the methylene urea polymer, the longer it takes for the N to become available. For ureaform and methylene urea products, the rate of mineralization is reflected by the cold water insoluble N (CWIN) content and its Activity Index. It is questionable if the very long methylene urea polymers are effectively used by the plant.
Reprinted from Selected Fertilizers Used in Turfgrass Fertilization by J. B. Sartain and J. K. Kruse, University of Florida Extension.
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