NITROGEN-FERTILIZATION OF SPRING WHEAT BY POINT-INJECTION

Point-injection is a new method of fertilizer application with possible advantages for wheat (Triticum aestivum L.) growing areas of the Northern Great Plains. A study was conducted to evaluate point-injection for N fertilization of spring wheat in southern Alberta. Field experiments at seven site-year combinations compared point-injection of urea NH4NO3 solution with the following conventional methods of granular N application: banded urea, banded NH4NO3, broadcast urea, and broadcast NH4NO3. Banded treatments were applied only as a preplant application, while broadcast and point-injection treatments were applied at one of five times, including preplant. There were no yield differences among any of the preplant application methods, nor was there a consistent significant difference among methods at individual sites. When averaged across sites and common application times, grain yields in point-injection treatments were 2 bu/acre higher than those in broadcast NH4NO3 treatments. Regardless of application method, wheat yields declined significantly when N was applied at the tillering stage or later. At three sites showing significant differences in 1989, grain yields in treatments receiving N at the five-leaf, tillering, booting, and flowering stages, averaged 98, 91, 81, and 70%, respectively, of those receiving N at seeding. At two sites, protein concentration was significantly increased by delaying application of N but protein yields were not increased because of lower grain yields. Point-injection is a viable alternative to conventional methods of N application for spring wheat. Because it provides effective N placement after seeding, point-injection af fords some flexibility in application time and allows adjustment in fertilizer rates in accordance with growing conditions.