This study determines the effect of N fertilizer placement, N fertiliser rate and N application timing on the competitive ability of wheat (Triticum aestivum L.) in dryland no-tillage cropping system in the Western Australian grainbelt.

The results of this study suggests:

• Whilst the streaming of UAN modestly reduced annual ryegrass N percentage in the tissue, no difference in annual ryegrass biomass or seed production was evident.
• Nitrogen placement did not affect Wheat biomass accumulation (NDVI results), however modest differences in Canopy closure percentage existed. UAN rate and timing however had a greater effect on wheat biomass (NDVI results and wheat biomass cut) and percent canopy closure.
• UAN rate, UAN timing (plus interaction of UAN timing and placement) were found to have significantly affected Radiation interception of the crop in the absence of weeds.
• Nitrogen placement affected the yield and protein content of the grain produced.