RESPONSE OF NO-TILL WINTER-WHEAT TO SEED-PLACED AMMONIUM-NITRATE FERTILIZER

Winter wheat (Triticum aestivum L.) can be successfully overwintered in most regions of the Canadian prairies if it is sown without prior tillage into standing stubble immediately after harvest of the previous crop. Soil nitrogen (N) is usually deficient in this production system and N fertilization is necessary to optimize yield and maintain minimum quality standards. In the present study, the effect of seed-placed (SP), early-spring broadcast (BC), and SP/BC combinations of ammonium nitrate fertilizer (AN) on winter survival, grain yield and protein production of winter wheat was investigated in 15 field trials conducted over a wide range of soil types and environmental conditions in Saskatchewan. Ammonium nitrate fertilizer placed in a 20-mm-wide band with Norstar winter wheat seed produced average grain yield responses for 34, 67, and 101 kg N ha-1 treatments that were 98, 84, and 71% of comparable BC treatments, respectively. Average grain protein yield responses for the 34, 67, and 101 kg ha-1 SP N treatments were 94, 82, and 74% of comparable BC treatments, respectively. Grain protein concentration responses were similar for comparable BC and SP N treatments. Yield responses for 34 kg N ha-1 SP and BC treatments indicated that AN could be seed-placed at low rates without significantly reducing N-use efficiency. However, significant reductions in winter survival potential in all trials where differential winterkill occurred suggested that even rates as low as 34 kg N ha-1 SP AN should be avoided when cultivars with marginal winter hardiness are utilized.