Evaluation empirical models of competitiv ability of four wheat varieties (Triticum aestivum L.) to Japanese borom (Bromus japonicus L.)

Background and objectives Weed management is one of the effective methods to maintain capacitance of production. weed density is a quantitative effective factor in competition with crop. nowadays in the management of weed communities, instead complete elimination weed of farm, work to recognition and quantitative assessment of the behavior and effects of weed in crop ecosystemse. This requires is knowledge of crop-weed properties during the growing season and their interaction and quantify of the competition. So far, several experimental models to express the relationship between crop yield loss in the presence of weed suggested. These models are used to understand concepts such as the intensity of competition and thresholds of weed control. Hence this study was done in order to assess the competation of various densities Japanese borom weed and four varieties of wheat (Hamun, Hirmand, Bolani and Kalak afghani) and prediction of yield loss using experimental models and compare its performance.
Materials and Methods This study was carried out to evaluate empirical models of competition, as based on a factorial arrengment using arandomized complete blocks design (RCBD) with 4 replications at field experiment was conducted at the Chah Nimeh field experiment station University of Zabol, in 2014-2015 growing season. In this experiment Hamun, Hirmand, Bulani and Kalak afghani cultivar were planted with density of 400 plants m-2. Simultaneously with planted of wheat, Japanese borom (Boromus japonicus L.) with densities of 0, 100, 150, 200. 250 and 300 plants m-2 were planted. At the end of the growing season, the final harvest of the lower half of each plot was performed by observing the marginal effect and in the area a square meter. To estimate grain yield loss of wheat cultivars in different levels of weed density was used of density-yield loss model, one-parameter and two-parameter models of relative weed leaf area and one-parameter and two-parameter models of relative weed dry weight. In this reaserch was used to softwares SAS and Sigmaplot and Excel to analysis of variance and estimation of model parameterse and plot graphs.
Results Our results based on yield loss models confirmed that biological yield decreased less than grain yield (Grain yield was more susceptible).Obtained relative damage coefficients (q parameter) of one and two-parameter models based on relative leaf area and relative dry matter were indicative of high competitive ability of japanese borom than wheat cultivars.Comparison of several empirical yield loss models showed that models based on relative leaf area and relative dry matter of Japanese borom with Minimum regression root mean square error, had more efficiency in predict of wheat grain yield loss in compared with yield loss-density model.
Conclusions Overall our results of this study showed that Japanese borom weed is exist a strong competitor to wheat cultivars. Also addition of weed density reduced grain yield and biological yield wheat varieties investigated linearly. Wheat cultivars were different of sensitivity to weed interference. Compare the performance models was suggested excellence of weed relative leaf area and dry weight relative models to density-yield loss model. As a result of these models can be used to a good measure to predict of wheat yield loss in interference with the Japanese borom weed.