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Fluid Journal : Fluid Journal 1993-1995
Drs. R.E. Lamond, W.B. Gordon, D.L. Fjell Subsur Subsur Subsur Subsur Subsurface Placement Best In face Placement Best In face Placement BestIn face PlacementBestIn face Placement Best In R RRRReduced- educed- educed- educed- educed-Til l Til l Till Till Till Kansas researchshowimportance ofnutrient management/hybrid selection in boosting crop yield Winter 1995 140 130 120 110 100 90 80 70 60 Yield (bu/A) Figure 1. Effect of placement method on yield of no-till grain sorghum, North Agronomy Farm, Lamond et al., Kansas State University, four-year averages. Check Broad- Dribbled Knifed cast Summary: Heavy residue cover can affect efficiency of surface applied nitrogen in conservation-till production systems. Research in Kansas has shown that placement of UAN is important in these systems. Best efficiency has been achieved with placement methods that put the UAN below surface residue. Placement of UAN in the soil away from the residue greatly reduces potential for nitrogen losses due to immobilization and volatilization. Heavy residue cover also results in cooler, wetter soils, particularly early in the growing season. Kansas research has shown that some short-season hybrids have responded to starter N-P applications when planted early in no-till production systems, even though residual soil fertility levels were high. Conservation-till production systems are used by an ever-increasing number of farmers across the United States. Conserva- tion tillage is really a catch-all designation that includes any production system that strives to leave a protective residue cover on the soil surface. Examples include no-till, reduced-till, ridge-till, and others. The value of residue in protecting top soil from wind and water has been well documented. On any soil that is highly erodible, December 31, 1994 was the date set for implementation of an approved farm conservation plan, in which residue cover is a major component. The efficiency of surface-applied nitrogen (N), for example, can be affected by such residue cover. Potential for immobilization (tie-up of N in decomposing residue) and volatilization is increased. Soils covered by a residue layer also tend to be cooler and wetter, particu- larly early in the growing season, which can affect N and phosphorus (P) needs. Mineral- ization release of N and other nutrients from organic matter will be slowed. P availability will also be affected. Subsurface band superior Several years of research evaluating N rates and methods of application for UAN in continuous no-till production systems have been conducted in Kansas. Results of a four-year trial involving dryland continuous no-till grain sorghum are shown in Figure 1. N was applied in late May every year. An excellent response to N was noted and placement of UAN below the residue (knifed in 4 to 5 inches deep on 20-inch centers) was superior to surface broadcast applica- tion. Surface banding (dribble on 20-inch centers) performed better than broadcast but not as well as the knifed placement. Differences in N efficiency due to placement were noted in leaf N concentrations (sampled at boot stage) and in grain protein concentrations. Research evaluating placement of UAN in dryland continuous no-till corn also has been ongoing. In the three-year study, N was applied in late April every year. Both placement methods that placed UAN below
Fluid Journal 1996-1998