Effect of nitrogen fertilization schedule and herbicide on competition between barley and ryegrass

ABSTRACT This paper reports the effect of different nitrogen (N) fertilization schedules, weather conditions, and herbicide use on the competition between barley (Hordeum vulgare L.) and a weed, ryegrass (Lolium rigidum). The ability of the weed to compete was increased by high rainfall during autumn and winter followed by low rainfall during the spring. Good distribution of rainfall during the growing season, however, favored the crop plant over the weed. In general, competition from Lolium rigidum reduced barley biomass, straw yield, grain yield, harvest index, total nitrogen accumulation, and nitrogen translocation efficiency to the grain. The nitrogen fertilization applied in the growth season was 120 kg ha− 1. Applying the entire complement of fertilizer during early barley tillering (N0 + 120) benefited ryegrass, increasing its ability to compete with the crop; regardless of herbicide use. When the full fertilizer complement was applied during the pre-sowing period (N120 + 0), or when half was appli...