Investigating the Possibility of Reducing dose of Bromoxynil+2,4-D and Nitrogen Fertilizer in wheat (Triticum aestivum L.) in Competition with Mallow (Malva spp.)

Abstract Bachground & objective: The competitive ability of weed is one of the key elements in describing the interactions of crops with weeds and predicting crop yield loss in sustainable agricultural systems. The aim of this study was to quantify the interactve effects of nitrogen fertilizer and reduced dose of bromoxynil+2,4-D on the competition of wheat–mallow.   Materials & Methods: An experiment was conducted in the research field of Agricultural Sciences and Natural Resources University of Khuzestan during 2016-2017 growing season. Experimental design was split block based on completely randomized block design with three replications. Experimental factors consisted of nitrogen level (0, 75, 150, 225 and 300 kg.ha -1 of urea fertilizer) as main plot and reduced dose of bromoxynil+2,4-D (0, 0.25, 0.5, 0.75 and 1 time of recommended dose (1.5 L.ha -1 )) as sub plots.   Results: Results showed that wheat biomass was the most in case of applying more doses of herbicide plus nitrogen fertilizer. However, it was the least without herbicide and fertilizer application. Nitrogen fertilizer (130 Kg.ha -1 )+recommended dose of herbicide (1.5 L.ha -1 ) or 220 Kg.ha -1 nitrogen fertilizer+50% recommended dose of herbicide and/or 300 Kg.ha -1 nitrogen fertilizer+55% recommended dose of herbicide can be used to achieve wheat biomass about 600 (g m -2 ). Mallow biomass was greatest without herbicide application and use of 300 kg ha -1 of urea fertilizer. Competitive ability of mallow (μ) increased with increasing nitrogen fertilizer use and reached maximum with applying of 150 (kg h -1 of urea), but the use of more than this, reduced the competitive ability of mallow.   Conclusion: In this study, wheat biomass was significantly reduced in competition with mallow, which was significantly higher in non-herbicide treatment than other treatments. Therefore, increasing urea consumption without mallow control will significantly reduce wheat biomass.