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Fluid Journal : Fluid Journal 1996-1998
Fall 1997 will be enhanced and ammonia volatilization reduced. _________________________________ Interest by researchers in ridge-till for row crop production continues because of its potential for conserving soil and water, and reducing costs of machinery, labor, and herbicides. Ridge-till, a very reduced-till system, allows early planting of corn and soybeans on poorly drained soils of the Midwest. In ridge-till, N placement options are limited for corn because of the absence of primary and secondary tillage, except for ridge scraping at planting and ridge building at cultivation. Consequently, many farmers use a "weed and feed" program where UAN (10 to 15 gal/A) serves as a carrier for herbicides and is band-applied on the crop row at planting. Remainder of the N is usually injected as anhydrous ammonia or sidedressed at cultivation as UAN. Although several N application methods have been evaluated over the years by researchers, none of these studies compared a wide range of N application methods and timing options for corn following soybeans in a ridge- till system. What has facilitated more placement and timing flexibility for N management in conservation tillage systems is development in 1989 of the spokewheel injector by Baker and associates. This injector places fertilizer directly into the root zone with little crop residue incorporation and minimal soil disturbance. Objectives of this study were: • Evaluate the spokewheel injector as a tool for precise UAN placement in a ridge-till system where corn follows soybeans • Evaluate the effects of N placement (band vs. broadcast vs. injection) and timing (single vs. split) on corn yield, net economic return to N, N uptake, and N recovery. Weather favorable Growing season conditions in 1986 and 1987 were ideal. Precipitation was slightly higher than normal. Temperatures were average to warmer than average. Although May to September rainfall was 36 percent below normal in 1989, and June rainfall was 57 percent below normal, timely rains coupled with the absence of high-stress temperatures produced good crops. UAN was moved into the soil profile to minimize volatilization losses of ammonia. Rainfall was also adequate each year to move sidedressed UAN into the active root zone. Because of very dry and abnormally hot conditions in 1988, yields were very low (less than 85 bu/A). Therefore, 1988 was Yield -- bu/A 160 150 140 130 120 110 100 90 AA, PP, INJ-V UAN, PE, BR UAN, PE, BDCT UAN, PE, PINJR UAN/UAN, PESDV7, BR/PINJV UAN/UAN, PESDV16, BR/PINJV Figure 1. Effect of N rate, source, timing and application method on corn yield; three-year average, Randall, et al., University of Minnesota. Check 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
Fluid Journal 1993-1995
Fluid Journal 1999-2001