EFFECT OF RATE, TIMING AND PLACEMENT OF N FERTILIZER ON STUBBLED-IN WINTER WHEAT GROWN ON A BROWN CHERNOZEM
Winter wheat (Triticum aestivum L.) production in Saskatchewan has increased in recent years due to the introduction of Norstar, a winter hardy variety, and due to the reduction in winter injury when the crop is seeded directly into standing stubble (stubbling-in). Large variations in the amount and distribution of seasonal precipitation in the Brown soil zone may prove detrimental to the adoption of this system. If implemented, fertilizer recommendations will need to be developed to fit this cropping system. A 4-yr study was conducted at Swift Current, Saskatchewan on an orthic Brown Chernozemic silt loam soil to determine the effect of rate, season of application, and placement of urea-N on grain yields and protein concentration of stubbled-in winter wheat. Plant density was unaffected by N. In 1984–1985 and 1986–1987 adequate weather conditions from seeding to early spring resulted in acceptable plant stands, but in 1985–1986 suboptimal winter temperatures and in 1987–1988 severe drought during fall and early spring reduced over-winter survival of wheat. Only 1 year provided better-than-average growing season weather conditions and thus good yields. Grain protein was < 11.5% (the critical lower level for milling) in two of the 4 years. In 1 year, a dry fall and winter coupled with a prolonged hot, dry early spring resulted in poor grain yields and very high protein concentrations (20–22%). Fertilizer-nitrogen, broadcast at 50 kg ha−1 at seeding, resulted in yields and grain protein concentrations similar to those when N was broadcast in April. Band placement of N was superior to broadcast application only in terms of grain protein concentration and N fertilizer recovery. There was no difference between banding N at 5 and 10 cm depth. In all years studied, application of N at 100 kg ha−1 was excessive for this system. It was concluded that producers should be cautious in attempting to grow stubbled-in winter wheat in the Brown soil zone.Key words: Yield, grain protein, N recovery, plant population, kernel weight