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Fluid Journal : Fall 2012
05 The Fluid Journal Fall 2012 Dr. Dale Leikam is President of the Fluid Fertilizer Foundation in Manhattan, Kansas. Table 5. Effect of Including Additional UAN with NPK Starter on No-Till Corn B. Gordon, KSU, 2011 NPK Starter Surface Band and 2 X 2 Placements Corn Yield, Bu/A No Starter 159 5+15+5 187 15+5+5 192 30+15+5 211 45+15+5 210 equipment, coulters, and even spoke wheels. All of these are easily adapted to UAN. As the number of crop acres under complete no-till management continues to increase, the benefits of subsurface placement of fertilizer N continue to increase as well. Managing N loss. Subsurface N placement of all required N is not always the most efficient practice in terms of agronomics and/or logistics. Leaching and denitrification are two soil N loss pathways that affect NUE. Leaching is the movement of nitrate-N through the soil profile and out of the crop rooting zone. Leaching is most common on coarse-textured, sandy soils. Denitrification is the conversion of nitrate-N to plant unavailable forms of N by soil microbes in saturated (low oxygen) soils. Both leaching and denitrification are associated with very wet conditions and UAN can be an integral part of a plan to manage these losses. Split applications that provide a portion of required N at or before planting, and another portion later in the season to the time of crop demand and uptake, can increase NUE and crop yields. Table 2 provides an example of the types of results that are possible when splitting the N application as compared to a single preplant application. Multiple N applications via irrigation systems are another way of improving NUE by minimizing leaching and/or denitrification losses. UAN is the common N source for split and/or multiple N applications since UAN may be easily and affordably adapted to these systems. Surface banding (also termed dribble applications) consists of directing coarse streams of UAN to the soil surface. It is a valuable tool for improving NUE in small grains, reduced- and no-till systems, and forage crops. Surface banding provides fertilizer N performance results approaching subsurface banding, but without the need of soil disturbance associated with subsurface applications. Benefits include reduced potential for immobilization of N in crop residues, reduced potential for urea-N volatilization losses, easy fit with split and/or multiple N applications, and reduced potential for foliage burn. Tables 3 and 4 present examples of surface banding advantages over broadcast N application from a brome grass study in Kansas and a Bermuda grass study in Texas. These same types of results have been demonstrated for field crops in no-till and reduced-till cropping systems. Surface banding of UAN is often overlooked as an improved N management practice in many areas. Along this same line are research findings demonstrating that surface banding (dribbling) liquid NPKS starter fertilizers on the soil surface beside the row at planting is about as efficient as traditional 2 x 2 starter applications. The advantage is that these surface band liquid systems can easily and affordably be retrofitted to existing planters, while 2 x 2 starter equipment cannot. Additionally, research has clearly demonstrated that taking some of the total N to be applied and placing it in the starter program is very beneficial. Adding the UAN to the NPKS starter to make a high N starter material provides consistent yield responses as compared to the NPKS starter by itself- -especially with high residue levels associated with reduced- and no-till systems. Table 5 provides research results that are typical for including a surface banded high N starter fertilizer in the row crop fertility program. An easy choice Over the years there have been many discussions about what N source is the best. Of course, it does depend on the specific field situation being addressed, but in general, what N source tends to be favored? If agriculture was limited to only a single N product to serve the entire marketplace, what should it be? Many would argue that direct-applied anhydrous ammonia should be that single product because it typically has the lowest purchase price per pound of N and it must be placed below the soil surface, which reduces the potential for certain N loss pathways. Others might favor urea, because unlike ammonia it can be easily and safely stored, handled and applied plus the fact that it is the most common N source globally. But specialized equipment is required for ammonia application and that equipment is somewhat costly and not easily adapted to many desired fertility program options. Also, the fact that ammonia is limited to direct application below the soil surface is a huge limitation relative to other N sources. And while urea is the dominant global N fertilizer, that is a reflection of limited infrastructure and equipment for other N sources that are not yet readily available in many regions of the world. Urea is also subject to potential volatilization loss under certain conditions and equipment for subsurface application is not as affordable or common for many producers. As a result, if we could have only one N source in the marketplace, it is an easy choice: UAN solution. Why? Adaptability and flexibility. In addition to issues related to safety, storage, handling, and equipment requirements, the main reason UAN is much more a universal N source than other N sources in the marketplace can be summed up in one phrase: unsurpassed adaptability and flexibility!
Late Spring 2012