Nitrogen levels and application methods affect weed biomass, yield and yield components in Tir’ wheat ( Triticum aestivum )

Abstract Nitrogen (N) fertilisation is an important component of integrated weed management systems in wheat ( Triticum aestivum ). This study was conducted to determine the effects of N and application methods on the weed‐crop competition in ‘Tir’ winter wheat ( T. aestivum var. leucospermum ) in the absence of herbicide. The trial was conducted in a factorial randomised complete block design with 4 replications in 2 years (2005–06 and 2006–07). Three N rates (0, 60, and 120 kg N ha −1 ) and three application methods ((1) broadcast on the soil surface; (2) banded 10 cm broadcast between every crop row; and (3) banded 10 cm deep between every crop row) were applied. Weed flora composition and density, weed biomass, grain yield, biological yield, plant height, spike length, number of seeds per spike, 1000 seed weight, and protein ratio in grain and shoot were investigated. The differences between treatments for weed density were not significant in either year. However, application of N up to 120 kg ha −1 increased total weed biomass to 1020 and 2009 kg ha −1 in the 2 respective years, whereas weed biomass of 643 and 862 kg ha −1 was obtained with 0 N ha −1 . Greatest weed biomass was recorded with N applied by broadcast and banded between crop rows, whereas weed biomass was least for N banded 10 cm deep with values of 722 and 1139 kg ha −1 in 2 successive years. Highest grain yields were obtained with 120 kg ha −1 N (1568 and 1190 kg ha −1 ) and for N banded 10 cm deep (1263 and 1132 kg ha −1 ) in the 2 successive years, respectively. Information gained from this study will be used to develop more efficient fertilisation levels and application methods in winter wheat as components of integrated weed management in the absence of herbicide.