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Fluid Journal : Fluid Journal 1993-1995
C.L.Mann and Drs.D.B.Mengel andS.E.Hawkins Injection is Most Efficient Method of Injection is Most Efficient Method of Inje ction is Most Efficient Method of Inje ction is Most Efficient Method of Injection is Most Efficient Method of UAN Placement UAN Placement UAN Placement UAN Placement UAN Placement Comparison trials show effects of timing, application methods, and nitrific ation inhibitors on no-till c orn yeilds. Summary: For no-till corn in the eastern Corn Belt, the most efficient time to apply N for uptake is to apply the majority of N at planting or after planting. Early preplant applications of N lead to a high level of N loss in the humid climate of this region. The most efficient method of N placement is injection below the surface. Placing N below the surface minimizes fertilizer residue contact and avoids immobilization and volatilization losses. Split applications, where a portion of N is broadcast and a portion injected later in the growing season, may be an attractive alternative to growers who want to use UAN as a carrier for herbicides, or do not have access to starter equipment, yet still hope to maintain high levels of N-use efficiency and corn yields. Applications of a portion of N as starter appeared to be beneficial in N management systems where N was injected into the soil at or near planting. However, in systems where a sizable amount of N was broadcast prior to emergence of the crop, starter nitrogen responses were minimal. No significant response to the use of DCD or ATS was observed in this study. However, consistent trends to higher N uptake and yield with the use of DCD were observed, suggesting that additional work on this product may be warranted. The project reported here provides a comprehensive evaluation of early preplant UAN applications in no-till corn production systems. It discusses timing and placement of applications, the use of nitrification inhibitors, and the use of starter fertilizers. This project was designed to compare interactions among these components, as well as their interaction with different residues and environments. Objectives of the project were: • Compare efficiency of early preplant UAN applications with at-planting, and delayed (V6 growth stage) • Determine effect of DCD, and DCD + ATS, at enhancing the effectiveness of surface-applied UAN as compared to delayed application or subsurface applications of the fertilizer • Compare the effectiveness of split applications of UAN • Determine the effect of starter fertilizer (N only) on corn growth when used in combination with a number of N application systems. Timing/placement Timing and placement of UAN had a definite effect on all measures taken. Several key observations can be made. Broadcast preplant and at-planting treatments, and injection at planting time produced the best early-season growth. Nitrogen applications delayed until the 6-leaf stage reduced early- season growth and N uptake. However, while broadcast applications gave greatest early-season growth, delaying N applica- tions until the V-6 stage resulted in the highest N uptake and yields (Figure 1). Note also that injecting UAN below the residue at planting produced a yield significantly higher than when broadcasting UAN on top of the residue at planting. These results are consistent with a number of previous studies conducted in Indiana and other states. Early preplant N application resulted in significantly lower total N uptake and yield, as compared to all other application times or 170 160 150 140 130 120 110 Yield N Uptake Yields -bu/A N Uptake - kg/ha Broadcast early Broadcast planting Inject planting Inject V6 190 180 170 160 150 140 130 Figure 1. Effects of timing and placement of UAN on N uptake and yield of no-till corn. Summer 1995
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