By Mitchell Japp, PAg, Provincial Specialist Cereal Crops, Regina
The 4Rs, right rate, right source, right place and right time, are a simple slogan to encourage producers to conscientiously apply fertilizer effectively, efficiently and economically. Given the many nitrogen (N) products on the market and countless combinations to apply them, applying N safely in a mid-row or side-band at seeding time remains prudent.
When it comes to efficiency, many farms experience logistical issues with supplying enough N to the air drill with minimal downtime. Limitations include on-farm fertilizer storage, trucking capacity and stops to fill that are too frequent. One option that may be overlooked is planning to include a top-dress or in-crop application of N.
A project evaluating post-emergent N applications was summarized in the last issue of CPN. Many projects have looked at post-emergent N applications, but with varied results. While results vary, applying N at seeding in a side-band or mid-row band is consistently as effective and economical as various combinations of post-emergent applications along with some at seeding.
A post-emergent N application is just one of the many combinations of 4R treatments being evaluated in a five-year project underway in Saskatchewan and Alberta. The project, Integrating N fertilizer technologies with superior genetics to optimize protein in CWRS wheat without compromising yield, 4R principles, and environmental health, was introduced in a Crop Walk video last year.
The project evaluates the following four timing and placement treatments of N:
- 100 per cent at seeding in a side-row band;
- 30 per cent at seeding, 35 per cent at Feekes GS4 (called "green up") and 35 per cent at Feekes GS10 (boot);
- 65 per cent at seeding and 35 per cent at Feekes GS10; and,
- Control with no added fertilizer.
Like many other studies on post-emergent N applications on the Prairies, the first year results showed variations. There were clear effects at all locations from timing and placement, but they weren't consistent at all locations. Three of five sites indicated the treatment with all N applied at seeding as high-yielding, but only in one location the yield was significantly higher than treatment three. The other two sites reported the highest yields with a post-emergent application (treatments two and three) – although they weren't significantly different. Growing season precipitation likely influenced the results, which ranged from excessively wet to extremely dry, and it is always difficult to draw conclusions from only one growing season.
There were no fertilizer treatments that were substantially penalized at four of five locations. So, if spring N logistics are challenging good N stewardship, consider applying N as a top-dress application. Generally, it seems to work best if about 2/3 of the crop N requirement is applied at seeding time, either in a mid-row or side-band. Top-dress N rates can be adjusted based on growth conditions, the amount of precipitation, tissue test results or measurements of the crop greenness by a GreenSeeker. Top-dressed urea and ammonium nitrate may burn leaves, but this will likely not alter yield and can be reduced by using streamer nozzles instead of spray or flat-flan nozzles. Timing of top-dressed N applications can vary, depending on the desired outcome. Earlier applications, such as Feekes GS4 or GS10 as used in this project, will contribute more to crop yield. Later applications, such as after anthesis, will contribute more to protein content. Rain is needed after the application to prevent volatilization losses from the applied N, which can increase the risk of delaying fertilizer application. However, the use of stabilizer in conjunction with granular or liquid applications reduces this risk.
Integrating N fertilizer technologies with superior genetics to optimize protein in CWRS wheat without compromising yield, 4R principles, and environmental health also evaluates varieties, N rate and N source, including several options of enhanced efficiency fertilizers. The project will continue at Lethbridge, Barrhead and Edmonton in Alberta, as well as Indian Head and Scott in Saskatchewan until 2023.
For more information about crop staging visit the Guide to Crop Protection or the Purdue University's article on Managing Wheat by Growth Stage.
For more information on N management, visit the Nitrogen Fertilizations in Crop Production page.