Effect of Amount and Methods of Nitrogen and Phosphorus Fertilizer Applications in Wheat weed Density and Growth

To investigate effect of the amount and the methods of nitrogen and phosphorus application on weed management of wheat، an experiment was performed as factorial، based on randomised complete blocks design with three replications at the Research Farm، Faculty of Agriculture، Ferdowsi University of Mashhad، Iran during 2009. Treatments included nitrogen at (100، 200، and 300 kg ha-1 phosphorus at 100، and 200 kg ha-1 and their application methods (Broadcast and Band application). Phosphorus source for fertilization was triple superphosphate applied soil incorporated before wheat sowing and N2 source was urea: 50% applied pre plant and 50% at shooting stage. The results showed that fertilizer application methods significantly affected wheat yield and weed biomass and density (p≤0. 01). Phosphorus and nitrogen band application method reduced weed biomass and weed density by 54% and 34% respectively and increased wheat biomass and seed yield by 21% and 36% compared to broadcast application method. The interaction effects of nitrogen and phosphorus application rate and also the interaction of phosphorus and nitrogen application methods showed that the fertilizer band application × 200 kg ha-1 phosphorus rate and 300 kg ha-1 nitrogen rate were the best treatment in wheat yield improvement and reducing weeds. These results indicated that by modifying fertilizer application methods and changing the amounts of their application، we may improve fertilizer use efficiency and weed management in wheat.