Q: Which crop nutrients applied generally provide the most yield response in any given year? What considerations should be made?
A: Crop yield response to nutrients depends on many factors. While the most important factor is moisture availability, other factors like crop selection, soil type, organic matter, residual soil fertility, previous crop, tillage, type of fertilizer and method of application can all impact your end result. Consistent soil testing helps refine the accuracy of fertilizer recommendations. Satellite imagery, yield maps and variable rate fertilization can provide further insight into how and where on your field you may gain enhanced bang for your fertilizer dollar.
While this may seem complicated, sometimes the simple is better approach can provide guiding principles to complex issues. For crop fertility, understanding crop yield response to specific nutrients is one guiding principle. An extensive research study completed several years ago by Crop Production Services reinforced the simple guiding principle that, in most crops, outside of legumes, nitrogen fertilizer is responsible for 70 to 80 per cent of the crop response to fertilizer. Phosphorus followed at 12 to 15 per cent, while potassium, sulfur and micronutrients followed that.
When it comes to fertilizer recommendations, nitrogen is the key nutrient to focus on first. This doesn’t mean we ignore the other nutrients — we simply give nitrogen first priority.
Norm Flore is a manager of agronomic services with Crop Production Services in southern Alberta.