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Fluid Journal : Fall 2012
Fall 2012 The Fluid Journal 04 of crop nutrients with fluid application equipment as compared to other dry and ammonia equipment. As a result, it is much easier, accurate, and cheaper to variably apply UAN across fields in modern precision agriculture systems as compared to other sources of fertilizer N. Adaptability. The ease of adaptability of UAN to a very wide range of crop production systems (no-till, reduced-till, perennial forages, etc.), crop nutrient placements (subsurface band, surface applied, surface bands, etc.), methods of fertilizer application (broadcast and incorporated, included in starter fertilizer, fertigation, etc.), and time of N application relative to crop growth (preplant, at planting, post-plant, etc.) have had a large effect on the increased adoption of UAN in modern crop production systems. While other N fertilizer products can be fit into some of these cropping situations, UAN is the only common N source that can be easily and affordably fit to all of these situations. Visit with researchers who study various crop nutrient application methods and you will most likely find that UAN is the product of choice due to the ease and cost of adapting equipment to various placements and timings. Agronomics Agronomic advantages of UAN relative to other N products are not due to the forms of N present in the product since it is no more than a combination of urea, ammonium nitrate, and water. However, there are many benefits associated with the fact that UAN is a non-pressure, fluid N source. It is the adaptability of UAN to a wide variety of cropping systems, a large array of efficient application equipment, and an accompanying multitude of nutrient placements and timings that sets UAN apart. '4R' concept. With continued increased emphasis on crop profitability and environmental stewardship, a relatively new term has come to the forefront in this regard---'4R' Nutrient Stewardship'. The 4R Nutrient Stewardship concept, initially developed by the International Plant Nutrition Institute, is increasingly being adopted by agriculture as a way of promoting and communicating fertility related best management practices (BMP's) to the public, agribusiness, and farmers. While the promotion of fertility BMP's is certainly not new, the 4R Nutrient Stewardship concept provides a clear, concise, and simple approach to increasing the adoption of BMP's in agriculture- -applying the appropriate rate of crop nutrients, in an efficient manner, at the right time, using crop nutrient products that are right for a specific situation. When 4R Nutrient Stewardship is mentioned, UAN should immediately come to mind. Relative to the '4R' concept, there are many methods/times of N application that come to mind: • preplant subsurface/band • surface band • surface dribble • starter application • sidedress • topdress • pivot fertigation • drip irrigation fertigation • weed and feed application • split applications • variable N rate application • spoon feeding • broadcast unincorporated • broadcast incorporated There has been much research conducted over the years on a variety of crops relative to various application methods and timings. While a few examples are detailed in the following discussion, it is beyond the scope of this brief review to discuss all of the relevant application methods and timings that have been studied. The Fluid Journal has published articles on many of these application methods/timings and can easily be searched in the Fluid Journal archives: (http://www.fluidjournal.org/ subscribe_archives.php) NUE. It has been known for a very long time that nitrogen use efficiency (NUE) can often be improved by subsurface banding of fertilizer N. Placement of N bands below the soil surface helps manage the immobilization of fertilizer N in decomposing crop residues and eliminates the potential for urea N volatilization losses. Additionally, placement of N bands below the soil surface provides for better 'positional availability' in the event that adequate rainfall does not occur to move surface-applied fertilizer N into the root zone. A few common N application methods that place fertilizer N below the soil surface include knifed applications, simultaneous application with tillage Table 3. Effect of UAN Application Method on Bermudagrass Production Habey et al., Texas A&M - 3 year average Bermudagrass Apparent UAN Method Yield Forage N NUE Lbs/A % % Surface Broadcast 13,927 1.55 51.7 Surface Band 15,007 1.6 61.9 Subsurface Band 14,110 1.62 55.8 Table 4. Application Method Effects on Bromegrass Lamond and Whitney, Kansas State University 5 site year average Bromegrass Forage Yield N Treatment 1987 1988 1989 1990 1991 5 yr average Pounds per Acre N Check 3034 1905 2530 2630 2950 2610 UAN Broadcast - 60 Lbs N/A 6085 3296 2930 6540 5050 4780 UAN Surface Band - 60 Lbs N/A 6258 4341 3330 7680 5510 5424 UAN Broadcast - 120 Lbs N/A 7083 4795 3060 8740 6320 6000 UAN Surface Band - 120 Lbs/A 7199 4736 3440 8780 5930 6017 Significant Level 0.1 0.05 0.05 0.05 NS ---
Late Spring 2012