Italian ryegrass (Lolium multiflorum Lam.) density and N fertilization on wheat (Triticum aestivum L.) yield in Argentina

Italian ryegrass (Lolium multiflorum Lam.) is an important and troublesome weed in cereal crops in Argentina. It is present in 46% of the wheat fields of the most important cropped area and its control is mainly performed by selective grass herbicides that represent a significant percentage of total production cost. Designing weed management strategies is necessary to reduce the dependence on herbicides. This requires improving our knowledge of the effect of different management practices such as N fertilization on weed-crop interactions. Given the importance of achieving a sustainable and efficient use of herbicides, field experiments were carried out at wheat field crops in Argentina between 2004 and 2006. The main objective was to evaluate the competitive effect of ryegrass at different densities on wheat yield and its components with different nitrogen fertilization levels. In addition, the effect of N fertilization on weed emergence, growth and fecundity was also studied. N fertilization increased ryegrass competitiveness. Ryegrass densities of 100 plants m−2 reduced wheat yield by 30% and 20% with and without N fertilization, respectively. N fertilization did not modify seedling emergence dynamics but increased ryegrass growth and fecundity. Individual fecundity was 190 and 118 seeds per plant on the average of fertilized and non-fertilized plots, respectively.

► Lolium multiflorum is one of the most troublesome weed in wheat and barley crops in Argentina.
► The dynamic of emergence of ryegrass was studied.
► The effect of N fertilization on ryegrass-wheat competition was studied.
► The effect of N was studied also on weed growth and fecundity.