Forage Crop Fertilization Guidelines
Soil Testing
For accurate fertilizer recommendations, conduct soil testing prior to forage establishment or on established stands.
- 0–6 inch depth: Use for established stands when sulphur levels are known to be adequate.
- 0–24 inch depth: Use before establishment or for full nutrient assessment.
Fertilizing Forage During Establishment
Phosphorus is most effective when banded 1 inch to the side and 1 inch below the seed. If banding is not possible, incorporate phosphorus and all other fertilizers into the soil before seeding.
Fertilizing Established Grass Stands
Annual broadcast applications of P, K, and S may be made in late fall or early spring. Avoid application to frozen soils where runoff may occur.
Nitrogen rates can be based on soil tests or economic considerations.
General Recommendations — Grass
Nutrient |
Rate |
Nitrogen (N) |
0–20 lb/ac following fallow; 40–60 lb/ac following stubble at establishment. For established stands: 90–110 lb/ac when forage prices are high and soil moisture is adequate. |
Phosphate (P₂O₅) |
25–40 lb/ac at establishment; 20–30 lb/ac on established stands. |
Potassium (K₂O) |
On sandy or organic soils: 45–90 lb/ac at establishment; 30–60 lb/ac on established stands. |
Sulphur (S) |
15 lb/ac sulphate-S on well‑drained or grey luvisol soils. Soil tests are recommended due to variable S availability. |
Nitrogen Sources and Management
- Ammonium nitrate is typically 10–15% more efficient than urea for the first cut.
- When volatilization risk is low, urea performs as well or better for late‑season and multi‑cut systems, often increasing forage crude protein levels.
- Volatilization losses are highest when urea is applied to moist thatch under warm, windy weather.
- Urease inhibitors can reduce volatilization for up to 14 days.
- N solutions perform best when surface‑banded, dribble‑banded, or injected. Broadcast N solutions are not recommended for established forages.
Timing for Grass Hay or Pasture
Relative efficiency of broadcast granular N:
- Spring (Apr–mid May): 100%
- Fall (October): 78%
Split applications (half in spring, half after first cut) provide similar yield to full spring application and help maintain consistent forage quality. Avoid split applications below 45 lb/ac N.
Fertilizing Legume Stands
Broadcast fertilizer may be applied in fall or early spring, avoiding frozen soils with runoff risk.
General Recommendations — Legumes
Nutrient |
Rate |
Nitrogen (N) |
Not recommended. Inoculate seed at planting. |
Phosphate (P₂O₅) |
55–75 lb/ac at establishment; 45–55 lb/ac on established stands. |
Potassium (K₂O) |
On sandy/organic soils: 55–150 lb/ac at establishment; 40–100 lb/ac on established stands. |
Sulphur (S) |
30 lb/ac sulphate-S on well‑drained and grey luvisol soils. Soil testing recommended. |
Micronutrients
- Boron is important for alfalfa. Deficiency symptoms include yellowing or reddening of young leaves.
- Deficiency is more common on high‑pH, sandy soils under drought stress.
- Confirm through soil and tissue testing.
- Where required, apply 1–2 lb B/ac, avoiding excess due to potential toxicity in sensitive follow‑up crops (e.g., oats, beans).
Grass–Legume Mixtures
- >50% legume: Nitrogen fertilization is unnecessary.
- <30% legume: Treat as a pure grass stand; N response is expected.
- Where feasible, re‑seeding mixtures with legumes is often more economical than applying nitrogen fertilizer.
Fertilizing Grass Stands
Annual broadcast applications of phosphorus (P), potassium (K), and sulphur (S) on established grass stands may be applied in late fall or early spring. Avoid applying fertilizer to frozen soils that are prone to runoff.
Nitrogen rates should be determined using soil test results or based on forage value and fertilizer cost.
Nitrogen rates should be determined using soil test results or based on forage value and fertilizer cost.
General Fertilizer Recommendations for Grass
Nitrogen (N)
- At establishment:
- 0–20 lb/ac following fallow
- 40–60 lb/ac following stubble
- Established stands:
- 90–110 lb/ac when forage prices are favourable and soil moisture conditions are good.
Phosphate (P₂O₅)
- 25–40 lb/ac at establishment
- 20–30 lb/ac on established stands
Potassium (K₂O)
- Sandy-textured or organic soils:
- 45–90 lb/ac at establishment
- 30–60 lb/ac on established stands
Sulphur (S)
- Apply 15 lb/ac sulphate-S on well‑drained soils and grey luvisol (grey wooded) soils.
- Sulphur deficiency can occur across many soil types and regions; a soil test is recommended to determine field S status.