SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/183915
FieldScience A NITROGEN CYCLE that shows where the various fertilizers' work is useful. and while urea used to be the product that was almost always coated, other fertilizer sources may now be coated (such as potassium sulfate). Slow-release N sources that are slow-release because urea has been converted via chemical processes into a slow-release N source. Slow-release fertilizers created by chemical reactions all start as urea. The most common product currently on the market in the turfgrass industry is ureaformaldehyde (UF), formed by reacting urea and formaldehyde to produce chain molecules of varying lengths. The length of the chains controls N release, with shorter chains having quicker N release for turfgrass use. Ureaformaldehyde reaction products are also often called Methylene ureas (MU) (as if it was a synonym with UF) but it is really not. Specifically, methylene-ureas tend to be the group of ureaformaldehyde reaction products that are intermediate in chain length, and have an N content of 39 to 41%. In comparison, a ureaformaldehyde that has long been on the market, Ureaform, has the longest chains, and is thus very slow in the release of N for plant use. Regardless of the chain length, N release occurs as microorganisms break the chains, releasing N which is available for plant use. The release patterns of ureaformaldehyde products are controlled by the length of the chains; the shorter the chain, the quicker the release. Additionally, some short-chain UFs are frequently marketed as liquid slow-release materials, such as triazone. Ureaformaldehyde fertilizers are quite popular in the turfgrass market, and there is a wide variety of products available for your use. Before choosing a specific fertilizer you should consult the fertilizer label to determine the relative N percentages that are rapidly or slowly available for plant use. 10 SportsTurf | October 2013 The other slow-release N fertilizer that is chemically slow release is isobutylidene diurea (IBDU). A combination of urea and isobutyraldehyde, IBDU does not depend on soil microorganisms for release but is broken down by water (hydrolysis) into urea. The rate of urea release from IBDU varies with particle size, temperature and moisture. The smaller the particle, the faster the release. The higher the temperature, the faster the release. Recent discussions with turfgrass managers reveal that few use IBDU, often because it is difficult to obtain. If available, it is an excellent material for cool-season use for long-term N supply because it does not require microbial activity for N release. Slow-release N sources that are slow-release because they are a 'true' natural organic material in which the N must be released via the biological process of mineralization. These natural organic slow-release N sources are generally manufactured from some type of waste material. Sometimes the material is composted to help reduce odors, or the material may be dried and granulated to improve handling and spreading characteristics. Common organic fertilizer waste materials include sewage sludge, poultry litter, meat-processing waste and other animal by-products such as fish or feather meal. Much of the N in such fertilizers is organic N in the form of relatively complex chemical compounds, and is not available for plant uptake until microbes have converted it into nitrate and ammonium. Soil temperature greatly influences microbial activity and the rate at which N is mineralized from these organic fertilizers. In cold soils, little activity will occur; an organic N fertilizer applied during winter in the northern US will just sit there with little N available for plant use until the soil warms. By contrast, fresh poultry litter applied to turf during hot weather is relatively quickly available, as most of the organic N is rapidly converted to nitrate and ammonium. Some relatively new N fertilizers on the market are blends of organic wastes, such as fish meal, feather meal or poultry litter, and a water-soluble inorganic N such as ammonium sulfate. Such a product would produce a rapid greening response from the inorganic N and an extended response from the organic N. These "hybrid" materials can still burn turf if you apply them at high rates, and the labels usually have a warning to that effect. Read the guaranteed RESEARCH TRIALS are often conducted to evaluate N release of various fertilizers over time. In this study, different N sources are applied to hybrid bermudagrass, and each week color, quality and clipping yield data is collected from each plot. www.sportsturfonline.com