YIELD AND YIELD COMPONENT RESPONSE OF SPRING BARLEY TO FERTILIZER NITROGEN

Barley (Hordeum vulgare L.) is an important cereal crop in eastern Canada, where it is used mainly as a source of energy for monogastric animals. A 4-yr field experiment was conducted to evaluate the effects of N application on the yield of spring barley. Three cultivars, Cadette, Leger (adapted feed types), and Argyle (unadapted malting type) were grown with 0, 50, 100, 150, or 200 kg N ha-1 applied as ammonium nitrate at seeding. Two other treatments consisted of 100 kg N ha -1 at seeding plus 50 kg N ha-1 as ammonium nitrate (broadcast) or urea (foliar spray) applied at Zadoks growth stage 50 (spike emergence). Grain yield generally did not respond to N treatments. Separate determination of main stem (MS) and tiller yield components revealed that the lack of response to progressively higher rates of N was due to the stable nature of MS yield components and to the relatively small contribution of tillers to grain yield. Very high levels of N occasionally reduced the grain set and yield of MS spikes. Mean weight per MS grain showed little variation among growing seasons and N treatments. High rates and split applications of N had few significant effects on tiller yield and yield components. Tiller spike densities were consistently low (81-147 spikes per square meter). Tiller spikes produced only 7 to 15 grains, with individual grains weighing 60 to 75% of the weight of MS grains. Previous cropping practices and environmental conditions seemed to affect spike development and grain-set more than application of fertilizer N.