Nitrogen fertilizer placement and timing affects bread wheat (Triticum aestivum) quality and yield in an irrigated bed planting system

Searching for sustainable cropping systems has often focused on the optimization of system sustainability, yield or ideally both. It is important to also include wheat quality characteristics like grain protein concentration (GPC) and bread-making quality (loaf volume). The effect of placement and timing of nitrogen (N) fertilizer on performance and quality of the bread wheat cultivar Navojoa, was tested in two tillage systems under furrow irrigation: conventionally tilled beds (CTB; new beds formed after disc ploughing and residue incorporation) and permanent beds (PB; only furrows reshaped and residues retained on the surface). N fertilizer (120 kg N ha(-1) as urea) was broadcast, applied in furrows or disk-banded on top of beds. The timing treatments were all fertilizer applied before planting or split between pre-planting and first node. Permanent beds had the highest yield and grain quality was highest with split bed and furrow application. Averaged over four years, N use efficiency and GPC were significantly higher in CTB (24.5 kg kg(-1) and 10.1 %, respectively) than in PB (22.2 kg kg(-1) and 9.9 %, respectively) indicating the necessity in PB for optimal N management to obtain stable yields and acceptable grain quality. A reduced number of cold hours and solar radiation negatively affected grain yield. Broadcast fertilizer application reduced grain quality and N use efficiency. N fertilizer management in furrow-irrigated wheat cropping systems should combine splitting the N dose and disking it on the bed pre-planting and in the furrow later in the season, depending on the crop needs at the application time.