Q: What are the advantages and disadvantages of top dressing nitrogen?
A: Top dressing nitrogen is one fertilizer option to help achieve yield goals. The advantages include increasing yield potential, increasing time efficiency and diffusing financial risk. Timing is key. The nitrogen needs to be applied early in the growing season and before a rain event to move the nitrogen into the soil.
To apply, use sprayers for liquid applications and spreaders or floaters for granular applications. The speed advantage using this machinery is two to three times faster than banding fertilizer.
Top dressing nitrogen will spread out the fertilizer investment risk. When growing conditions are favourable for high yields, growers can reap the benefits of increased yield potential. Alternatively, growers control total nitrogen applications when conditions are not conducive to high yields (for example, during a drought).
The disadvantages of top dressing include the struggle of applying nitrogen at the correct time and potential for increased nitrogen losses. Although top dressing is a quick job to complete, it often needs to be completed when growers are busy finishing seeding or starting in-crop herbicide. Another challenge is weather not co-operating to complete the application. The largest disadvantage when top dressing is the potential for nitrogen loss due to volatilization (gas-off).
Using a urease inhibitor product to treat nitrogen will reduce the potential for volatilization and increase the efficiency of the nitrogen application. Also, consider the 4Rs of Nutrient Stewardship; apply the “right” nitrogen product at the “right” rate with a urease inhibitor, aim for the “right” time before a rain (using streamer nozzles), and the “right” place, balancing soil-applied fertilizer with foliar applications to manage top dressing nitrogen to its full advantage.
Nathan Trowell, CCA,PAg, is a manager of agronomic services with Nutrien Ag Solutions in eastern Saskatchewan.