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Optical sensors have potential for determining nitrogen fertilizer topdressing requirements of canola in Saskatchewan

Holzapfel, C.B., Lafond, G.P., Brandt, S.A., Bullock, P.R., Irvine, R.B., James, D.C., Morrison, M.J., May, W.E. (2009). Optical sensors have potential for determining nitrogen fertilizer topdressing requirements of canola in Saskatchewan, 89(2), 411-425. http://dx.doi.org/10.4141/CJPS08127

Abstract

Holzapfel, C. B., Lafond, G. P., Brandt, S. A., Bullock, P. R., Irvine, R. B., James, D. C., Morrison, M. J. and May, W. E. 2009. Optical sensors have potential for determining nitrogen fertilizer topdressing requirements of canola in Saskatchewan. Can. J. Plant. Sci. 89: 411-425. An important challenge in N management is matching fertilizer inputs to crop requirements for specific environmental conditions. Field experiments were completed over 3 yr at two locations in Saskatchewan to evaluate the feasibility of using optical sensors and high-N reference plots along with topdressed liquid urea ammonium-nitrate (UAN) to arrive at more optimal N rates for canola (Brassica napus L.). Treatments included N management strategies where the timing and methods of application were varied along with the total quantities of N applied. Sensor-based N management was compared with the predominant practice of banding predetermined amounts of N at seeding. On average, sensor-based N management resulted in a 34 kg N ha-1reduction in fertilizer use with no effect on seed yields except at Indian Head in 2006 where dry conditions resulted in yield reductions of 370 to 454 kg ha-1compared with applying canola's entire N requirements at seeding. Sensor-based N management or split-N applications never increased yields relative to applying all N at seeding. Adopting this technology in western Canada will more likely result in reduced N inputs without reducing yield than increased seed yield. While sensor-based N management did not reduce post-harvest residual soil NO3-N levels, agronomic N use efficiency (ANUE) was increased 33% of the time and was never lessened. When significant, the increase in ANUE ranged from 4.8 to 7.8 kg seed kg N applied-1. Overall, optical sensors have potential as a tool for managing N fertility more efficiently in canola production.

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