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Fluid Journal : Fluid Journal 2002-2004
Fall 2003 Alternatives To Fall N Applications Via Fluids Dr. Gyles Randall and Jeffrey Vetsch Summary: Due to favorable weather conditions, corn yields exceeded 200 bu/A. In a one-pass field cultivate sys- tem, greatest yields were obtained when 40 lbs/A of N as UAN was dribbled at planting or broadcast preemergence ("weed and feed") in combination with 60 lbs/A of N sidedressed at the V3 stage. Lowest yields occurred when 20 to 40 lbs/A of N as UAN was dribbled next to the row at planting in combination with 80 or 60 lbs/A of N applied as anhydrous ammonia in the fall. In the strip-till system, highest yields were obtained when all of the N was sidedressed as UAN or split between 40 lbs/A of N as UAN broadcast ("weed and feed") during preemergence and 60 lbs/A of N sidedressed as UAN. Lowest yields occurred when 40 lbs/A of N as UAN was applied close to the seed row at planting in combination with 60 lbs/A of N sidedressed as UAN. all application of nitrogen (N) is under severe scrutiny throughout the Corn Belt largely because of greater potential for N loss in the spring before crop uptake. Numerous studies have documented significant loss of nitrate-N in subsurface tile drainage water during February through June. Some long-term studies show that 65 to 70 percent of the an- nual drainage discharge and nitrate losses occur in April, May, and June. These early-season losses are being associated with development of the Study looks at different application timing under two distinctly different corn tillage systems. hypoxic zone in the Gulf of Mexico. For these reasons, fall application of N is being questioned and is in jeopardy throughout much of the Mississippi River Basin. Soil erosion and sediment delivery to surface water bodies are also burning issues as society looks for improved water quality. Agriculture has a signifi- cant role to play in this process and for years has advocated the use of conser- vation--till practices to minimize erosion and sediment loss to surface water bod- ies. Two different conservation-till sys- tems involving no primary tillage after soybeans were used in this project. One, and the newer of the two, is a strip-till system that spaces strips on 30-inch centers tilled about 8 inches deep with knives mounted on a tool bar much like an anhydrous ammonia appli- cator. The knife tills an area 4 to 6 inches wide and leaves a 1- to 2-inch berm of residue-free soil. The inter-strip area is left untilled and is covered with residue. Placement of fertilizer, espe- cially P and K, about 6 inches deep at the time of strip preparation is consid- ered to be an agronomic and environ- mental benefit of strip-till. The other is a one-pass system that involves a full-width field cultivator just prior to planting corn. This is a popular system that creates a favorable, weed- free seed bed and is extremely suitable for incorporating spring preplant fertiliz- ers and herbicides. The objectives of this study were to determine the effect of planting time and sidedress applications of UAN as alternatives to traditional single fall and spring preplant N treatments on corn after soybean in two different tillage systems. YIELDS AT 200+ One-pass, field cultivate. Corn yields for 2002 in Table 1 exceeded 200 bu/A for some N treatments. These high yields were due in part to favorable rain- fall (20.18 inches) during the May to September growing season, especially in August (6.08 inches). Also contrib- uting was 6 percent above-normal grow- ing degree units (GDU) for the growing season, which ended on September 24. Wet conditions during June (7.15 inches) caused some leaching and deni- trification. In general, greatest yields were ob- tained with: • UAN split-applied between plant- ing and sidedress • Fall-applied anhydrous ammonia in combination with 20 or 40 lbs/A of N sidedressed as UAN. • Fall-applied anhydrous ammonia with N-Serve • Single preplant applications of anhydrous ammonia, urea or UAN. Lowest yields occurred for split treat- ments of fall anhydrous ammonia plus either 20 or 40 lbs/A of N as UAN dribbled on the soil surface near the row at planting. Fluid Journal F
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