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Fluid Journal : Fluid Journal 2005-2007
FALL 2006 Fluid Journal 21 • Prevailing temperatures • Moisture • Soil type. But, regardless of these factors, surface strip applications usually equal or exceed broadcasting as shown in Table 1, and often are similar to AN. Subsurface banding is even better than surface strip because it brings in the added advantage of reduced positional availability from dry surface soils and eliminates the possibility of volatilization losses. A response of corn to the different application methods is depicted in Figure 1. Multiple-nutrient applications in surface or subsurface strip applications may have even more benefits. Including ammonium thiosulfate (ATS) in UAN can affect urea hydrolysis and nitrification with improvements in NUE as well as providing plant nutrient sulfur (S) as shown in Table 2. Combinations of UAN and 10-34-0 have long been recognized as an improved mechanism for delivering both N and P to plants through stimulated ammonium N absorption and slowed P fixation reactions. N-P2O5 ratios of at least 1:1 seem to be a key in these benefits. UAN additives UAN additives admittedly increase N costs but the improved use efficiency offsets that additional investment. Agrotain. UAN is half urea so additives such as Agrotain (NBPT), which is a urease enzyme inhibitor and slows urea hydrolysis, can produce advantages in N management. It keeps N in the urea form longer and provides greater opportunity for incorporation by rainfall or irrigation, an advantage Figure 1. Corn response to UAN application methods. Table 2. Effects of UAN + ATS on no-till grain sorghum yields, 10 percent ATS by volume, Kansas. N rate Method of Yield Tissue N lbs/A application lbs/A % 0 3,584 1.57 50 Broadcast 5,488 2.06 50 Broadcast + ATS 5,768 2.17 50 Dribble 5,544 2.13 100 Broadcast 6,720 2.52 100 Broadcast + ATS 7,504 2.68 100 Dribble 7,280 2.70 Lamond and Whitney, KSU for surface applications that may be subject to ammonia volatilization losses and immobilization. Length of time additive affects urea hydrolysis is related to the amount of material coated on urea or added to UAN. One distinct advantage of this product is it increases the safety margin for broadcast. At the same time, there are a couple of disadvantages in using this product: • Cost ($3 to $6/A) • Limited protection time (5-14 days). N-GUARD is another UAN additive that can increase NUE with both broadcast and strip UAN applications in high-residue situations (Table 3). This high-charge density dicarboxylic copolymer is also effective coated on urea and Table 1. UAN placement compares favorably with ammonium nitrate for fescue at a rate of N at 120 lbs/A. Locations 1 2 3 4 5 yield -- lbs/A Check 4,707 1,257 615 3,664 4,017 UAN broadcast 6,412 4,758 3,274 6,002 6,911 UAN dribbled 6,925 5,787 4,064 5,900 6,872 AN broadcast 6,301 5,389 3,893 6,144 6,658 Kansas 0 20 40 60 80 100 120 140 160 180 200 Corn Yield (bu/A) 90 180 270 N Rate (lbs/A) Broadcast Spray Surface Band Subsurface Band Touchton, Hargrove, 1982 is theorized to provide suppressive effects on the urease enzyme through sequestration of the nickel ions in urease. Recommended concentrations are 1 percent in UAN and 0.25 percent coated on urea.
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