The effect of ryegrass (Lolium italicum L.) stand densities on its competitive interaction with cleavers (Galium aparine L.)
Italian ryegrass (Lolium italicum L. cv. Tetraflorum) seed production is an important industrial activity in Serbia. Cleavers (Galium aparine L.) interferes in Italian ryegrass seed production as well as in many other crops. The effect of stand density of Italian ryegrass on its competitive interaction with cleavers was investigated in western Serbia in the 2005-2006 and 2006-2007 cropping seasons. The established density treatments of Italian ryegrass were 5 kg ha-1 seeding rate with 60 cm row spacing (SD1), 5 kg ha-1 with 20 cm (SD2), 20 kg ha-1 with 60 cm (SD3), and 20 kg ha-1 with 20 cm (SD4). The interaction between Italian ryegrass and cleavers was evaluated by SPAD reading, relative nitrogen content (RNC) in the leaf, total nitrogen content (TNC) in the leaf, and seed yield. The rank order of the competitive ability of Italian ryegrass was SD4 > SD3 > SD2 > SD1 under optimal weather conditions for crop development. Under climatic stress conditions, however, neither effect of ryegrass densities nor cleavers was pronounced on competitive ability of ryegrass with different stands.
Key words: Relative nitrogen content (RNC) in the leaf, SPAD reading, total nitrogen content (TNC)