Effect of Common Mallow (Mava spp) Competitiveness on Grain Yield and Yield Components in Wheat under Different Levels of Nitrogen

In order to study the effect of mallow weed competition and nitrogen (N) rates on grain yield and yield components of wheat cv. Chamran, a field experiment was conducted in 2009. The experiment was designed as a split-plot with three replications and additive series. The N application rates were assigned in the main-plots (50, 100, 150 and 200 kg.N.ha-1) and sub-plots consisted of target common mallow (Mava spp) densities (0, 5, 10, 15 and 20 plant.m-2). Result indicated that, the effect of nitrogen (N) treatments, weed density (WD) and N×WD on grain yield (GY) was significant in 1% probability level. Grain yield decreased significantly as the WD increased. Grain yield reduction in high weed densities was due to lower spike per square meter (Sm-2), grain per spike (GN) and 1000-grain weight. Under the density of 20 mallow plant.m-2, GY, Sm-2, GN, spikelet per spike and 1000-grain weight losses was 27%, 15%, 10%, 6% and 6%, respectively. Wheat grain yield loss attributed to mallow weed ranged from 7 to 32% at 50 kg.N.ha-1 to 9 to 21.8% at 200 kg. N. ha-1. The highest and the lowest weed individual dry weight was belonged to 200 and 50 kg.N.ha-1, respectively. Agronomic N efficiency (ANE) of wheat decreased as the weed density increased. Wheat grain yield in mallow infected plot generally enhanced with N fertilization, while the density of mallow weed increased. Wheat competitiveness, GY and ANE were improved as N rate increased.