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Fluid Journal : Fluid Journal 1993-1995
methods. Applying N six to eight weeks prior to the initiation of the corn crop's grand vegetative growth stage makes N vulnerable to loss for a long period. In the humid climate of the eastern Corn Belt, it is likely that denitrification losses would be high most years. DCD/ATS Neither dicyandiamide (DCD), a nitrification inhibitor, nor ammonium thiosulfate (ATS), a reported urease inhibitor, had any statisti- cally significant effect on corn growth or grain yield in these studies, though there was a clear trend for enhancement of yield from the use of DCD (Figure 2), suggesting that additional work may be warranted. There were no indications that ATS had any beneficial effects on corn in these studies. Split vs. single A clear trend towards improved N-use efficiency, as measured by greater N uptake and higher yields, has been noted as a portion of the N is applied subsurface or later during the growing season. Growers willing to use multiple applications can provide excellent fertilizer-use efficiency by broadcasting half of their N early preplant as a carrier for herbicides, and injecting the balance at V-6 (Figure 3). Starters Starter N and its effect on yield was analyzed separately from the total data set because data was available for only one test site in 1993 and both in 1994. Starter N significantly enhanced early- season growth as measured by height at V- 6. While there were no significant effects of starter on nitrogen nutrition of the crop, starter did significantly increase yield. This supports earlier findings from Indiana and Alabama. Interaction between starter use and N timing and placement is shown in Figure 4. Note that when starter was used with injected preplant treatments, a large and highly significant yield response was found. Sidedress-injected N applications with starter enhanced early growth but not yield. This was probably due to extremely dry conditions after planting at both locations both years. Applying N late put N in dry soil with limited root activity and opened soil for further drying. No significant response to starter fertilizer, either in early growth or yield, was observed when starter was used in combination with an early-season broadcast application of N. This supports the findings of many farmers who have reported no starter response in no-till corn when they used UAN as a carrier for their preemerge herbicide applications. The trend toward higher yields with starter when UAN was applied in an early preplant broadcast application is probably due to enhanced N-use efficiency from the later application, and lower loss of N from the starter. Fine-tuning for no-till Weed and feed. No-till growers have a number of options for applying N. These include different fertilizer materials, and timing or methods of application. Many producers spray UAN directly on the soil surface as a preferred method of applying both nitrogen and herbicides. This method is popular because it accomplishes two tasks--weed control and nitrogen applica- tion--in one field operation, lowering machinery, labor, and fuel costs. The early application of herbicide prior to germination and emergence of many annual weeds also reduces the need for a contact or burndown herbicide, saving considerable money. However, little research has been done to date on the effectiveness of early-season applications of N. Past research and observations of farmer's fields suggest that 160 150 140 130 120 110 Treatment Yields -bu/A Broadcast Early Plant Inject at Planting Broadcast Pre-Broadcast at Planting Broadcast Pre-Inject at V6 Broadcast at Planting Inject at V6 Broadcast Pre-Inject at Planting Figure 3. Comparison of split application to single application on no-till corn yield. 156 154 152 150 148 146 144 142 None DCD DCD + ATS Figure 2. Effects of DCD and ATS on no-till corn yield. Yields - bu/A Summer 1995
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