The Effect of Nitrogen Fertilizer Application on Wild Oat (Avena ludoviciana L.) Competition Ability with Winter Wheat (Triticum asetivum L.) in Kermanshah Climate Condition

Introduction Cereals are the main agricultural production. Wheat is an annual crop, which plays an important role in human’s source of food. Wheat grains have various nutrients such as carbohydrates, proteins and various amino acids. The annual per capita consumption of wheat is about 232 in Iran, which is about double time of the world capita consumption. Weed interference decrease the quality and quantity of wheat production. Weed management in wheat farms is one of the main cost and time-consuming practices. Wheat yield decrease significantly by weed competition. Therefore, effective weed management dependents on knowledge about the effect of competition on yield and yield components. Response of the yield and yield components to weeds competition is different in crop species during the growth period. Yield components in development stages show the maximum sensitivity to weed competition. Wild Oat is the most important weed in wheat fields. Synchrony in development stages of wild oat with development stages of wheat is much more important reason in reducing of wheat yield and yield component. On the other hand, wild oat damage on wheat yield and yield components depends on several factors including species, plant density, wheat cultivars, nutrients consumption, sowing date, row spacing, and other ecological conditions. Moreover, leaf area index, plant height, leaf area density in canopy determine competitiveness of wild oat among wheat. Therefore, the objective of the present study was to evaluate the effect of wild oat competition in different plant densities and levels of Nitrogen fertilizer consumption on yield and yield components of wheat under Kermanshah climate. Materials and Methods This study was conducted to evaluate the competition of wild oat and winter wheat at the Research Farm of Campus of Agricultural and Natural Resources of Razi University during 2014-2015. The experiment was arranged in a split plots based on randomized complete block design with four replications. Treatments included amounts of 30, 60, 100, and 120 % of wheat demand to nitrogen fertilizer as a main plot and wild oat plant density of 0, 25, 50, 75 and 100 in m-2 as a subplot. Fertilizer applications were based on soil test recommendations at the rates of 250 kg ha-1 urea and 100 kg ha1 super phosphate triple. All phosphate and 1/3 of urea fertilizer were applied at planting, and 2/3 of urea was applied later. The experimental farm was ploughed using a mold board plough and then it was disked twice before sowing. Wheat and wild oat seeds were planted on November 20. Wheat plant density was 400 plants m-2. The experimental plot includes 10 planting row of three meters length with 25 cm row spacing. Wild oat seeds were collected from surrounding farms and pocket companies. In order to breaking wild oat seed dormancy was used KNO3 2% about 24 hours. Irrigation was done using a surface method based on plant demand. Analysis of variance was conducted by SAS software (version 9.4). Also, post-anova analysis performed to slicing interaction of nitrogen fertilizer application and wild oat plant density. The comparison of means was done based on LSD at 5% level. Results and Discussion The results showed that number of spike per square meter (24%), number of grain in spike (31%), 1000 grains weight (19.4%), grain yield (49.82%), wheat total dry weight (54.1%) and wild oat total dry weight (54.2%) improved by increasing of Nitrogen fertilizer application from 30 to 120 % wheat demand. Also number of spike per square meter (12.8%), number of grain per spike (23.5%), 1000 grains weight (21.8%), grain yield (38.9%), and wheat total dry weight (27.7%) decreased by increasing of wild oat plant density from zero to 100 plant per square meter. The results of interaction of nitrogen fertilizer application and wild oat plant density showed that the extent of wild oat damage on yield and yield components of wheat were increased with the increasing of nitrogen fertilizer application. Conclusions Our results demonstrated that higher resources absorption by wild oat and converting them to biomass compare to wheat increased the ability of wild oat in competition for resources and production of higher biomass and, consequently caused to more damage on yield and yield components of wheat especially with more nitrogen fertilizer application. In addition, it can be concluded that an increase in application of nitrogen fertilizer to higher than wheat demand not only did not improve wheat yield and yield components but also wild oat damage increased