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Fluid Journal : Winter 2011
Winter 2011 The Fluid Journal 10 heavier-textured Brandon site, the upper slope position may have drained and warmed sufficiently by the late seeding date to allow rapid, uniform emergence, as indicated by the higher stand density, while the lower slope position may still have contained excess moisture. At the Phillips site, biomass yield tended to be higher at the upper slope position with early seeding, but not with late seeding. The upper slope position would be better drained with somewhat warmer soil temperatures than the lower slope position, therefore would perform better with early seeding than would the lower slope position. Biomass yield at heading increased with N application at both locations, but the magnitude of the increase was small at the Brandon site (Table 1). At the Brandon site the split application of N, with the in-crop N applied late in the growing season, produced a lower biomass yield than when all N was applied at seeding on the late-seeded lower slope. The same trend occurred in the other slope positions and seeding dates, so the effect was significant overall. The half rate of N applied as urea at seeding gave yield similar to the full rate, so the reduction in biomass yield from the late split application may have been due to foliar burn. On the upper slope position, biomass yield at heading was also higher with CRU than with the early split application. There was greater response of biomass yield at heading to N application at the Phillips farm, particularly on the lower slope position, reflecting lower available N at this site (Table 2). The yield with the split application was similar to that with the half rate of N, indicating that the extra N added in-crop with the split application was not used efficiently by the crop. Grain yield. Grain yields at both locations were average to above average due to the adequate moisture and relatively cool growing conditions. On the Brandon site, the early seeding date produced significantly lower yields than the late seeding date (Table 3). In the preceding years, early seeding led to higher yields, so the abnormal results in this season were likely related to the unusual environmental condition that occurred in 2009. Very cool early- season temperatures and late-spring fronts led to poor early growth, which Table 4. Effect of nitrogen source, rate and timing on wheat grain yield (bu/A) of upper and lower slope postions, with early and late seeding dates, Phillips 2009 Lower Upper Source Rate Timing Early Late Mean of Lower Early Late Mean of Upper Site Mean Control 0 Control 32.4 35.8 34.1 37.9 42.7 40.3 37.2 Urea 1 Fall Band 43.4 46.1 44.8 47.6 44.3 45.9 45.4 CRU 1 Fall Band 46.2 47.1 46.6 46.2 47.4 46.8 46.7 Urea 0.5 Spring Band 40.6 42.5 41.5 43.4 43.6 43.5 42.5 Urea 1 Spring Band 47.6 48.8 48.2 45.8 51.1 48.5 48.3 Urea 1.5 Spring Band 51.9 54.4 53.2 48.0 53.1 50.6 51.9 CRU 0.5 Spring Band 42.8 44.6 43.7 45.3 44.6 45.0 44.3 CRU 1 Spring Band 48.3 46.2 47.3 47.4 44.3 45.9 46.6 CRU 1.5 Spring Band 54.1 52.7 53.4 43.4 47.3 45.3 49.4 SuperU 1 Spring Broadcast 47.5 43.5 45.5 47.7 44.2 45.9 45.7 Agrotain 1 Spring Dribbled 41.9 45.0 43.5 43.6 45.3 44.5 44.0 Urea-UAN 1 Split-Early 45.3 43.6 44.4 46.2 43.6 44.9 44.7 Urea-UAN 1 Split-Late 45.7 50.4 48.0 45.0 43.9 44.5 46.2 translated into reduced final grain yields with early seeding. There was no significant difference in grain yield between the upper and lower slope positions, however there was a slope-by- date interaction where the grain yield was particularly low on the early seeding date on the upper slope position. Grain yield only increased with N application at late seeding and there were no significant differences among N treatments. Grain yield was increased with N application at the Phillips site at all positions and with all seeding dates, but there were interactions between treatment and date and treatment and slope position (Table 4). On the lower slope position, grain yield increased with each increment of spring-banded urea up to the 1.5 times rate. Grain yield was higher when N was banded in the spring than in the fall. The fall-banded CRU produced grain yields that fell between the fall-banded and spring- banded urea, indicating that there was some benefit using CRU for fall application. Grain yield with broadcast Super U was lower than with spring-banded urea with the late seeding on the lower slope position. Similarly, use of Agrotain and surface- banded UAN produced lower yields than the spring-banded urea, with early seeding on the lower slope position. Application of half of the N as UAN in an early split application produced lower grain yield than spring-banded urea on the lower slope position with late seeding. Surprisingly, the late split application produced similar grain yields to the spring-banded urea. The spring- banded CRU produced higher grain yield than the Agrotain-treated surface dribble-banded UAN. Yields were similar with spring-applied urea and fall-applied CRU, indicating a benefit of the CRU in reducing losses. The spring-applied CRU produced lower yields than the similar rate of untreated urea. With late seeding, delays in release of CRU may have reduced yield potential. Yields were also lower with Super U and Agrotain Plus than with the untreated urea, indicating that the surface applications led to poorer efficiency than the in-soil banding, even with the use of inhibitors. When averaged over seeding dates and slope positions, use of the enhanced efficiency products did not provide an advantage over in-soil banded urea at the time of seeding on the Phillips site in 2009. Straw yield. Straw yield on the Brandon site was higher with late seeding than early seeding and higher on the upper than lower slope position (Table 5). Straw yield increased with N application but there were no significant differences among N treatments. "Controlled release urea (CRU) may be a more efficient form of N when banded in the fall."
Early Spring 2011