Build and Maintain your soil
Soil testing is a valuable tool for managing crop nutrition, especially in Ontario where nutrient levels play a crucial role in crop yields. According to the Ministry of Agriculture, Food and Rural Affairs (OMAFA), fertilizer recommendations based on soil test results can vary depending on the approach chosen.
One common method is the "Build and Maintain" approach, which focuses on building up soil nutrient levels over time, particularly for phosphorus (P) and potassium (K). This method often requires higher fertilizer inputs initially, but aims to ensure that nutrient levels are sufficient to support crop growth in future years.
Recent research by Dr. Dave Hooker at the University of Guelph-Ridgetown Campus compared this method with a sufficiency approach, which only applies enough fertilizer to match the crop's immediate needs.
The study showed that building soil test levels to moderate values (20 ppm P and 120 ppm K) improved yields across multiple crops, including corn, soybeans, and wheat. For instance, yields of corn increased by 5.9 bushels per acre, soybeans by 0.8, and wheat by 6.7 bushels per acre when moderate soil test levels were maintained.
When deciding how much fertilizer to apply, the crop's nutrient removal and economic factors such as fertilizer prices and long-term field goals must be considered. For example, a corn crop yielding 200 bushels per acre will remove about 84 lbs of phosphorus and 56 lbs of potassium per acre. Applying 15% more than the crop’s removal rate will help build up nutrient levels in the soil.
However, there are risks associated with building soil levels, particularly the potential for nutrient runoff. To mitigate this, it’s recommended to incorporate fertilizers into the soil or apply them via subsurface banding to reduce the risk of loss through water runoff.
The timing of nutrient application also plays a role, with spring and summer applications being more effective than fall or winter applications.
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