Grain Protein Response of Spring Barley to High Rates and Post‐Anthesis Application of Fertilizer Nitrogen

Barley (Hordeum vulgare L.) is an important feed crop in eastern Canada. Although the grain is used mainly as a source of energy for monogastric animals, high grain protein concentration (GPC) is desirable. Commencing in 1987, a 4‐yr field trial was conducted at the E.A. Lods Agronomy Research Centre of McGill University to evaluate the effects of N application on the GPC of spring barley. Cadette and Leger, which are adapted feed cultivars, and Argyle, an unadapted malting type, were grown with N rates of 0, 50, 100, 150, and 200 kg N ha−1 broadcast at seeding as NH4NO3. Two other treatments consisted of applying 100 kg N ha−1 at seeding and 50 kg N ha−1 as NH4NO3 (broadcast) or urea (foliar solution) 6 to 10 d after awn emergence. Increasingly higher rates of N applied at seeding increased the amount of protein per grain, thereby increasing GPC. The amount of nonprotein dry matter (DM) per grain was consistent among treatments within seasons. In only one instance did fertilizer N increase GPC by reducing nonprotein DM per grain. Split N treatments increased GPC significantly more than a single application of equivalent N at seeding in only two seasons. A foliar‐applied urea topdressing generally increased GPC more effectively than broadcast NH4NO3. With individual cultivars, the GPC response to N treatments could be explained in terms of protein per grain. Cultivar differences in GPC were not always related to protein per grain. Argyle had the highest GPC values (129.1–160.6 g kg−1), but only because of poor nonprotein DM accumulation per grain.