By John Ippolito, PAg, Crops Extension Specialist, Kindersley
Post-emergent nitrogen applications are used to increase wheat protein and sometimes yield when yield potential is high. The two suggested timings for post-emergent applications are pre-boot and post-anthesis. Pre-boot applications are used to increase yield and possibly protein while the late application will contribute to an increase in grain protein.
In 2018, a number of the AgriARM sites collaborated with SaskWheat to conduct the study "Increasing Wheat Protein with a Post Emergent Application of UAN."
Nitrogen rates used were 70, 100 and 130 pounds per acre side banded. An additional 30 lbs nitrogen per acre was applied post-emergently as both foliar and dribble band applications at pre-boot and post-anthesis timing. These treatments were only applied to the initial side band treatments of 70 and 100 lbs of nitrogen per acre.
The in-crop application of 30 lbs nitrogen per acre tended to increase yield and often resulted in a significant increase in grain protein content. The increases were no greater than if the additional 30 lbs nitrogen per acre had been applied in the side-band at seeding. Figures 1 and 2 show the yield and protein response across all sites.
The protein increases from post-emergent applications were roughly 0.8 per cent for the treatments where 70 lb nitrogen per acre was the sideband treatment. When the side band treatment was 100 lb nitrogen per acre the protein increase from post-emergent applications was 0.6 per cent on average. Whether this practice provided an economic benefit will have to be further evaluated.
In 2018, we had below normal seasonal precipitation at all locations that may have impacted the results. In a wetter year, results may have differed due to more losses from sideband applications and less potential for loss from the post-emergent applications.
Post-emergent nitrogen applications provided a benefit in a situation where the original nitrogen application was less than required to meet the crop yield potential. Otherwise applying the appropriate amount at or before seeding appears to be the best management strategy.