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Fluid Journal : Fluid Journal 2005-2007
10 Fluid Journal EARLY SPRING 2007 seeding, with the balance applied post-emergently, resulted in yields similar to applying all N at the time of seeding. However, the dry year of 2003 showed us that applying 33 percent of needed N at the time of seeding was not enough. Where no N was applied at seeding and all N was applied post-emergent, the yields were better when applied at the 3-leaf stage than the 1- or 5-leaf stage. This may simply reflect better rainfall immediately after the surface application, again emphasizing the need for rainfall to move N into the soil. Scott, SK site 2004. There was no significant overall grain yield or grain protein (Figure 2) response to N. An August frost and elevation differences were probable causes. Indian Head site, 2005. We observed an overall response to N and no differences between treatments where all the N was Figure 3. Effect of N starter levels on spring wheat yield via mid-row banding, Indian Head, SK, 2005. when a coulter was used to place the fertilizer in the soil in a year like 2003, the yield potential was still not regained. In situations of adequate and timely rainfalls, the coulter provided no advantages over the surface dribble bands. The conclusion was that some N would need to be applied at time of seeding and the proportion would more than likely be greater than 33 percent of the recommended N needs. There is also an urgent need to determine the latest crop stage feasible for applying the N fertilizer without jeopardizing the crop's yield potential. The other important aspects of this approach deal with risk management of N applications, especially in the drier areas of the Northern Great Plains. Rainfall unpredictability is such that producers are looking at approaches such as post-emergent N applications where all the fertilizer does not have to be put down at time of seeding. Also, with the development of active optical sensors, it is possible to increase NUE based on crop N need and application timing but we need to understand the risks of post- emergent N applications. The objective of this study was to quantify more accurately the risks associated with post-emergent N and how to reduce them. Spring wheat Indian Head site, 2004. Response to N starter levels on yield is shown in Figure 1. Overall, grain yields were higher where some starter N was used at seeding, with the balance applied as a surface dribble band, than when all N was applied as a surface dribble band. Adding just 33 percent of the total N requirements at time of Figure 4. Effect of N starter levels on canola yield via mid-row banding, Indian Head, SK, 2005. 33 35 37 39 41 43 45 Yield bu/A % N at Seeding Check 100 67 50 33 0 33 35 37 39 41 43 45 47 Yield bu/A % N at Seeding Check 100 67 50 33 0
Fluid Journal 2002-2004
Fluid Journal 2008-2009