EFFECTS OF NITROGEN APPLICATION ON YIELD AND QUALITY OF BROMEGRASS HAY IN CENTRAL ALBERTA

Abstract

Field experiments were conducted at four locations in central Alberta to determine the effect of N applications on dry matter yield and quality of bromegrass (Bromus inermis L.) hay. Ammonium nitrate was broadcast in early spring for 5 yr at rates of 0, 50, 100, 150, 200 and 300 kg N ha−1. In addition, fertilizer N was applied at 200 and 400 kg ha−1 only in the initial year to determine residual effects. Total dry matter yield (TDY) increased with increasing fertilizer N rates maximizing at 150 to 200, 100 to 150, 50 to 100 and 100 to 150 kg N ha−1 at Lacombe, Joffre, Botha, and Rocky Mountain House, respectively. Protein concentration and protein yield in bromegrass hay also increased with increasing N applications. Over the 4-yr period, TDY with initial N applications were generally lower than with the same total amount of N applied with annual rates. The residual effect of initial rates of N lasted only 2–3 yr following fertilizer application. With the exception of the Botha location, levels of NO3-N potentially toxic to livestock (>0.226%) were produced only in the first year. Potentially toxic NO3-N levels did not generally occur at those rates required to maximize TDY.Key words: Ammonium nitrate fertilizer, Bromus inermis, dry matter yield, nitrate-N concentration, protein concentration, protein yield