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Fluid Journal : Fluid Journal 1996-1998
Fall 1997 three years. UAN banded on the ridge at the 140-lb N rate produced the greatest uptake. Similar to grain yield, few and very slight differences in total uptake were found between N sources or among the times and methods of application in 1987 and 1989. In 1986, however, total N uptake was consistently greater for UAN spokewheel injected at preemergence than either preplant anhydrous or UAN band applied at preemergence. Because of the positive effect of spokewheel injected UAN at preemergence, total N uptake was greater with single applications of UAN compared with split applications of UAN and anhydrous ammonia. Three-year averages for the 100-lb/A treatments showed greatest N uptake with spokewheel injection of UAN directly into the ridge prior to emergence. In general, spokewheel injection of UAN, regardless of placement, gave greater total N uptake than did surface banding UAN on the row. N recovery Apparent recovery of N was highest (57 percent) with the single spokewheel injection of UAN into the ridge at preemergence (Figure 3), outperforming injected anhydrous ammonia by 7 percent and 18 percent higher than broadcast UAN. Apparent recovery was calculated on total N uptake of a treatment minus total N uptake in the control divided by the total N application rate. Procedure Site. Research was conducted from 1986 through 1989 at the Southern Experiment Station in Waseca, MN. Soil was a poorly drained Webster clay loam with about 5.5 percent organic matter. Since levels tested high, no additional P or K was applied. Rotation. Corn followed soybeans each year. Ridges were built when soybean height was about 24 inches. Soybean residue was evenly distributed across the experimental area with a straw spreader mounted on the combine at harvest. Ridge height before planting averaged about 5 inches. Plant density. Pioneer 3737 was planted each year in 30-inch wide rows at 30,400 plants/A. Less than 0.5 inches of soil was removed from the ridges during planting. Weed control was achieved each year by broadcasting a tank mix of alachlor and cyanazine at preemergence. Experimental design was a randomized, complete block with either four or five replicates. Plot size was 10 feet wide by 55 feet long. _________________________________ Dr. Randall is professor/soil scientist and Dr. Iragavarapu was formerly research associate at the University of Minnesota Southern Experiment Station, and Dr. Bock is research scientist at the Environmental Resource Center, TVA. ! N recovery -- % 60 55 50 45 40 35 30 25 20 AA, PP, INJ-V UAN, PE, BR UAN, PE, BDCT UAN, PE, PINJR UAN/UAN, PESDV7, BR/PINJV UAN/UAN, PESDV16, BR/PINJV Figure 3. N recovery as influenced by N rate, source, timing, and application method; three-year average, Randall, et al., University of Minnesota. 100 60 100 140 100 100 100 30+70 30+70 30+70 30+70 N Rate --- lbs/A UAN, PE, PINJV UAN/AA, PESDV7, BR/PINJV BR=Band on Ridge, PP=Preplant, PE=Preemergence, BDCT=Broadcast, PINJR=Point Inject in Ridge, PINJV= Point Inject in Valley, SD=Sidedress
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