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Fluid Journal : Winter 2014
5 The Fluid Journal Winter 2014 “Highest NUE achieved with high NRG-N” • Enhanced growth during dry spells • Increased cold and heat tolerance • Increased pest and disease resistance • Maximized plant health and quality • Improved internal circulation of the plant. Foliar application also helps to minimize N mineralization, denitrification, runoff, and leaching- -the pathway of loss association with soil-applied fertilizer. It has been suggested that foliar-applied N is readily taken up, translocated, and utilized. Lower risk of N loss and effective N uptake imply that smaller quantities of fertilizer could be sufficient to satisfy crop N requirements and to effectively correct N deficiency mid-season. Some research results suggest that foliar fertilization could be up to 20 times more efficient than soil application. From the point of view of practicality, the majority of foliar N fertilizers is easy to transport, store, and calibrate. Furthermore, they are compatible with many other fertilizers and chemicals such as herbicides. Combined application of premixed chemicals saves time, labor, and money. Many studies indicate that foliar fertilization is most useful when soil conditions limit nutrient availability. For example, alkaline soils do not readily release most metallic nutrients such as iron (Fe), manganese (Mn), and zinc (Zn). Foliar application has been successfully used to effectively alleviate these micronutrient deficiencies. Nitrogen is a macronutrient needed in much larger quantities compared to micronutrients. Nitrogen is a highly mobile element, both in the soil and within the plant. Some scientists point out that application of N to the soil targeting root uptake makes much more sense, because leaves may not be able to take up N in amounts adequate to satisfy the entire plant’s needs. Furthermore, foliar application of nutrients such as N often results in leaf burn as water evaporates and the fertilizer salts remain behind. Some research suggests that significant ammonia loss may occur following foliar applied N fertilizers, which in fact decreases NUE. Using stream-jet or flood nozzles, mixing the liquid N with additional water, applying less than 65kg N ha-1 per application, and avoiding applications on very warm or very cold windy days were shown to minimize concerns associated with leaf burn. Foliar N products Several foliar N fertilizers are currently available on the market. These products vary in analysis and can include N products or mixtures of N plus other macro and micro nutrients. Some of the N foliar fertilizers include: • Urea ammonium nitrate (UAN) • Liquid urea (LU) • NRG UAN. The most widely used foliar N fertilizer is UAN. Urea ammonium nitrate (28-0 -0 or 32-0 -0) is a non- pressurized solution that can be used in a variety of application practices. The liquid mix of UAN has been on the market for a long time. It provides a fast acting and long-lasting plant nutrient supply in a combination of three forms of nitrogen: • Nitrate-N provides quick response • Ammonia-N provides a longer lasting response • Organic N in urea provides sustained feeding. However, foliar application of UAN has been recognized as the least recommended option for N application by some researchers. Early in the growing season, foliar application of UAN may cause leaf burn, but mid- and late-season applications can reduce grain yields due to burn injury caused to leaves. Liquid urea is a water-based urea solution (20-0-0). LU’s proposed benefits include: slower uptake by the plant, which helps to maintain N levels within the soil plant system. LU is recommended for application during the warm growing months of the year for rapid correction of N deficiency. Research on foliar application of LU to crops is very limited. Generally, it is noted that where dry urea functions effectively, LU should perform equally well or better due to having the advantage of higher uniformity over some dry urea sources. NRG is a proprietary fluid product having an analysis of 27-0 -0 -1S derived from ammonium nitrate, urea, and ammonium sulfate. Additionally, it is said to include trace amounts of secondary/micronutrients as well as proprietary flavonol technology. Montana study The primary reason for foliar N fertilization in wheat is increased grain yield and improved quality-increased grain protein content. As noted earlier, protein yield represents an important parameter for evaluation of NUE in spring wheat. Previous studies in wheat showed that protein content was increased from 11 to 21 percent and from 15 to almost 17 percent. Most success in protein increase has been reported when foliar application was done just before or immediately after flowering. Many wheat growers are already using foliar products or considering including them as a part of their nutrient management plan. These producers are in need of up-to-date and unbiased information about currently marketed foliar N fertilizers. Our study aimed to answer the following questions: • Are LU and NRG agronomically and economically superior to UAN in improving spring wheat grain yield and protein content? • What is the optimum dilution ratio of foliar fertilizers and the threshold at which spring wheat grain yield is reduced to leaf burn? The field study, funded by Montana Fertilizer Tax Advisory Committee, was initiated in the spring of 2012. Three experimental sites were established: • Two dryland, one at Western Triangle Agricultural Research Center (WTARC) near Conrad, MT, and another in a cooperating producer’s field (Jack Patton, Choteau County, MT) • One irrigated at Western