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Effect of Nitrogen Rate and Placement and Seeding Rate on Barley Productivity and Wild Oat Fecundity in a Zero Tillage System

^a Agriculture and Agri-Food Canada (AAFC), Lacombe Research Centre, 6000 C & E Trail, Lacombe, AB, Canada T4L 1W1
^b AAFC, Lethbridge Research Centre, 5403 1st Avenue South, Lethbridge, AB, Canada T1J 4B1
^c AAFC, Brandon Research Centre, Box 100A, R.R. #3, Brandon, MB, Canada R7A 5Y3
^d AAFC, Beaverlodge Research Farm, Box 29, Beaverlodge, AB, Canada T0H 0C0

^* Corresponding author (odonovanj{at}agr.gc.ca).

Placing N in the form of urea with the seed allows seeding and fertilizer application to be accomplished simultaneously with minimal soil disturbance. However, seedling damage can occur from excess seed-placed urea. The objective of this study was to compare the effects of seed-placed and side-banded N (urea) applied at different rates on barley (Hordeum vulgare L.) density, maturity, and yield and wild oat (Avena fatua L.) fecundity, and to investigate if increasing the barley seeding rate would improve the ability of barley to overcome urea-induced injury and compete better with wild oat. A field experiment was conducted at three locations in western Canada over 3 yr. Nitrogen was applied as urea at five rates (0, 30, 60, 90, and 120 kg ha^–1 actual N), either directly with the seed or as a side-band, at three barley seeding rates (200, 300, and 400 seeds m^–2). When N was placed with the seed, barley plant density decreased, while time to maturity and wild oat fecundity increased as N rate increased. Barley yield also decreased but only at N rates above 60 kg ha^–1. Placing N as a side-band did not reduce barley density, resulting in shortened time to maturity, increased barley yield, and lower wild oat fecundity as compared to seed-placed N. Increasing the seeding rate increased barley density and reduced time to maturity and wild oat fecundity but did not affect barley yield.

Abbreviations: NBPT, N-(n-butyl)-thiophosphoric triamide • SBU, seed bed utilization

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Received for publication October 20, 2007.