NO-TILL WINTER-WHEAT PRODUCTION - RESPONSE TO SPRING APPLIED NITROGEN-FERTILIZER FORM AND PLACEMENT

No-till seeding into standing stubble immediately after harvest of the previous crop has permitted the successful production of winter wheat (Triticum aestivum L.) on the Canadian prairies. In the present study, 14 field trials were conducted in Saskatchewan between 1986 and 1988 to evaluate the influence of the spring broadcast and the surface banded N fertilizer forms ammonium nitrate (AN), urea, and urea-ammonium nitrate (UAN) solution on grain yield (GY), grain-protein yield (GPY), and grain-protein concentration (GP) of no-till winter wheat. In trials with positive N response, early broadcast urea, surface dribble-banded UAN, and broadcast spray UAN produced GY(GPY) responses that were 90(91), 89(87), and 82(80)%, respectively, of those observed for early broadcast AN. Accumulated surface residues and delayed early spring (May) rainfall reduced the performance of UAN when applied as a broadcast spray. In one trial, the early stimulation of N uptake and growth with early AN proved detrimental under high temperature stress during stem elongation resulting in negative GY and GPY responses with increasing N rate. Delaying broadcast N application by 3 wk prevented early N uptake, reducing both GY and GPY and increasing GP. The results of this study suggest that the reduction in N recovery from commercial rates of urea-based fertilizers, as measured by GPY, can be minimized at uniform levels by ensuring early spring application on no-till winter wheat in western Canada.