Cultivar Specific Fertility Management to Improve Nitrogen Yield in Wheat Seed.

Nitrogen (N) is the most limiting nutrient in crop production systems and N fertilization increases yield.  However, when N fertilizer is not used by crop plants it can enter the soil, water and atmosphere where it causes environmental degradation.  Small plot field research trials were conducted to measure N yield in the harvested grain of 12 different wheat cultivars, in 9 site years, at 5 different growing environments across Alberta, Canada.  The N fertilizer rate applied at seeding was based on soil tests and the growing environment’s yield potential.  In addition to N applied at seeding, there were 2 in-crop N treatments, an untreated control or 34kg N ha^-1 dribble banded as Urea Ammonium Nitrate at BBCH 30.  Percent N yield was calculated as = (seed N content * seed yield) / N fertilizer applied.  Percent N yield is used to allow comparisons between locations with different N fertilizer application rates. Nitrogen yield averaged 104% and ranged from 73 to 153% based on the site year, with higher N yield at locations with higher precipitation and/or irrigation.  There were significant differences between cultivars in 8 of 9 site years (p≤0.05).  The Canadian Western Red Spring wheat cultivar, AC Harvest had the lowest N yield in the harvested grain (average 93%) in 3 of 9 site years.  In contrast, a Canadian Western Special Purpose cultivar Sparrow had the highest N yield in the harvested grain (average 124%) in 5 of 9 site years.  The high N yield of Sparrow was attributed to consistent high yields (6.5 t ha^-1, 16% higher than the average) with moderate protein content (average 11.6%).  Sparrow was bred at the KWS-UK Research and Breeding Center in the United Kingdom and released in 2008.  If N fertilizer application rates are based on the cultivar needs, environmental degradation attributed to excess N use could be reduced while still achieving high yields.