Rooting for Success: Fall Soil Sampling & Fertilizer Tips
Soil Sampling
Soil sampling is the critical first step for soil fertility planning. Fall soil samples should be collected when soil temperature is consistently below 10 °C. This is to ensure soil microbial activities has slowed down and minimal changes occur between fall and spring. Taking samples in the fall also allows enough time for lab analysis, creating a detailed fertility plan for each field, and potentially taking advantage of fertilizer pricing.
When variability exists in a field, a composite sample of the whole field may not be representative. If that is the case, collecting soil samples by landscape position (hilltops, mid-slopes, depressions) is a very useful strategy. Twenty to 25 samples per landscape position should be collected for each field.
If a field is uniform, or if it’s a newer piece of ground and you need an idea of soil characteristics such as pH, electrical conductivity, or % organic matter, taking 20-25 samples and compositing them together to send to the lab will suffice.
Keep your eye out for a more in-depth Grain Exchange article featuring sampling strategies based on goals.
Video - Growing Smarter: Soil Sampling
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Fall Fertilizer Application
Soil test results combined with crop nutrient removal rates can create a more accurate soil fertility plan. When applying fall fertilizer, consider a few tips to minimize nitrogen loss throughout winter:
Apply when soil temperature is below 5 °C. This minimizes microbial activities that convert nitrogen to more loss-prone forms
Use subsurface banding instead of surface broadcast. Urea can quickly gas off especially under hot, dry, and windy conditions.
Use enhanced efficiency fertilizers. If nitrogen loss is a concern, use a urease inhibitor or dual inhibitor product such as SuperU, ESN or N-Serve.
If applying anhydrous ammonia in the fall, deep band into the soil and make sure the band is properly closed
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