Soybean Fertilizer Rates in Ontario
Nitrogen, phosphate and potash guidance for soybean in Ontario, taken from the OMAFRA Agronomy Guide for Field Crops (Publication 811) soil-test sufficiency tables.
Typical Ontario yield goal: 50 bu/ac. Micronutrient to watch: Mn.
Nitrogen: zero
Money is better spent on inoculant for fields new to soybean, on potash where the soil test calls for it, and on Mn where deficiency is confirmed.
Phosphate (P₂O₅) by soil test
Find your Olsen P value and read across.
| Soil test | P₂O₅ rate | P₂O₅ rate | Expected response |
|---|---|---|---|
| 0–3 ppm | 80 kg/ha | 71 lb/ac | High response |
| 3–5 ppm | 60 kg/ha | 54 lb/ac | High response |
| 5–7 ppm | 50 kg/ha | 45 lb/ac | High response |
| 7–9 ppm | 40 kg/ha | 36 lb/ac | High response |
| 9–12 ppm | 30 kg/ha | 27 lb/ac | Medium response |
| 12–15 ppm | 20 kg/ha | 18 lb/ac | Medium response |
| 15–30 ppm | 0 kg/ha | 0 lb/ac | Low response |
| 30–60 ppm | 0 kg/ha | 0 lb/ac | Rare response |
| over 60 ppm | 0 kg/ha | 0 lb/ac | No response |
Potash (K₂O) by soil test
| Soil test | K₂O rate | K₂O rate | Expected response |
|---|---|---|---|
| 0–15 ppm | 120 kg/ha | 107 lb/ac | High response |
| 15–30 ppm | 110 kg/ha | 98 lb/ac | High response |
| 30–45 ppm | 90 kg/ha | 80 lb/ac | High response |
| 45–60 ppm | 80 kg/ha | 71 lb/ac | High response |
| 60–80 ppm | 60 kg/ha | 54 lb/ac | Medium response |
| 80–100 ppm | 40 kg/ha | 36 lb/ac | Medium response |
| 100–120 ppm | 30 kg/ha | 27 lb/ac | Medium response |
| 120–150 ppm | 0 kg/ha | 0 lb/ac | Low response |
| 150–250 ppm | 0 kg/ha | 0 lb/ac | Rare response |
| over 250 ppm | 0 kg/ha | 0 lb/ac | No response |
Timing and placement
No N needed — inoculate seed well with rhizobium, especially on fields out of soybeans 3+ years. Apply P & K in fall or spring (banding shows little benefit over broadcast). If nodulation fails and plants are pale, 50 kg/ha N at first flower can rescue the crop.
No soil test?
Without one you are guessing. As a fallback, soybean removes roughly 14.5 kg P₂O₅ and 25.5 kg K₂O per tonne of grain, so replacement rates can hold soil levels steady — but replacement is not a recommendation. It cannot tell you whether you are already at 20 ppm and wasting money, or at 5 ppm and losing yield. Get a test from an accredited lab.
Cutting the fertilizer bill on soybean
- Credit manure before you buy anything — see available nutrients in manure and compost.
- Credit the nitrogen carried in MAP or DAP against your N requirement.
- Stop applying phosphate and potash where the soil test says no response is expected.
- Compare products on cost per unit of nutrient, not price per tonne.
Related guides
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