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 (N_{0 + 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 (N_{120 + 0}), or when half was applied during pre-sowing and half during early crop tillering (N_{60 + 60}), the Lolium rigidum biomass recorded was the same (although less than obtained with the N_{0 + 120} schedule). The N_{60 + 60} schedule led to greater barley biomass and nitrogen accumulation than the N_{120 + 0} schedule. When rainfall was well distributed over the growth season, the barley grain yield did not vary with respect to fertilization schedule. However, when rainfall was intense during the autumn/winter, the greatest grain yield was achieved with the N_{60 + 60} schedule, followed by the N_{120 + 0} and N_{0 + 120} schedules.

Keywords::

• annual ryegrass
• barley
• competition
• nitrogen fertilization