Forage Crops: Fertilizer
For specific recommendations, have your soil tested. Sample soil at 0-6 inches and 6-24 inch depths before establishment or on established stands. Sampling to 0-6" is useful only on established stands where sulphur levels are known to be sufficient.
When establishing forages, phosphorus fertilizer is applied most effectively by banding one inch to the side and one inch below the seed. If phosphorus cannot be banded, incorporate it and all other fertilizer into the soil before seeding.
Fertilizing grass stands
Annual broadcast applications of phosphorus, potassium and sulphur fertilizer on established grass crops may be made in late fall or early spring. Do not apply fertilizer to frozen soils subject to water runoff. Rate of nitrogen fertilization can be based on soil test levels or value of the crop and cost of fertilizer (refer to Manitoba Agriculture, Food and Rural Initiatives fact sheet Economics of Grass Hay Fertilization).
General Recommendations
| Nitrogen (N): | At time of establishment, apply 0-20 lb/acre N following fallow, 40-60 lb/acre N following stubble. Apply 90-110 lb/acre N to established stands when forage price is high and soils are moist. |
| Phosphate (P2O5) | Apply 25-40 lb/acre at time of establishment and 20-30 lb/acre for established stands. |
| Potassium (K2O) | On sandy-textured or organic soils, apply 45-90 lb/acre at time of establishment or 30-60 lb/acre to established stands. |
| Sulphur (S) | Apply sulphate sulphur at 15 lb/acre on well-drained soils and grey luvisol (grey wooded) soils. Sulphur deficiency may occur in many soils and in any area of the province. A soil test is recommended to establish the available sulphur status of fields. |
Sources of Nitrogen
Ammonium nitrate is generally 10-15% more efficient than urea in increasing the yield of the first cut of grasses. Manitoba studies have found that under conditions of minimal volatilization loss, urea forms are equal to or superior to ammonium nitrate for fertilizing late season grasses in multiple harvest systems and grass pasture. In these instances, hay or pasture grasses fertilized with urea can have higher crude protein levels than those fertilized with ammonium nitrate.
Volatilization losses of surface applied N may be very high if rainfall is not received soon after application. Volatilization losses are greatest when urea is applied to a moist thatch cover, followed by warm, windy weather.
Performance of N solutions are improved by surface band or dribble application. Treating urea with an urease inhibitor will delay volatilization losses for up to 14 days.
Broadcast N solutions are not satisfactory for established forages. To increase efficiency of nitrogen application with N solutions, they should be surface or dribble banded or injected into the soil with equipment such as a spoke wheel applicator.
Time of application
Grass for Hay or Pastures - The relative efficiency of broadcasting granular nitrogen fertilizer on established grass is as follows:
- Spring application: April to mid-May (100 percent)
- Fall application: October (78 percent)
Split-rate nitrogen applications (applying one-half the required N in the spring and the other half immediately after the first cut) is comparable to a single spring application.
The split-rate technique has the added advantage of equalizing the production of forage with a relatively higher protein content throughout the growing season. It is also useful for pasture production where rotational grazing is practised. Split application of less than 45 lb/acre N is not recommended.
Fertilizing legumes
Annual applications of fertilizer on established legume crops may be in the fall or early spring. Do not apply to frozen soils subject to water runoff. Additional information is contained in the Manitoba Agriculture, Food and Rural Initiatives fact sheet Fertilizing Alfalfa Forage.
General Recommendations
| Nitrogen (N) | Nitrogen is not recommended. Inoculate legume seed before planting. |
| Phosphate (P2O5) | Apply 55-75 lb/acre at time of establishment and 45-55 lb/acre for established stands. |
| Potassium (K2O) | On sandy textured or organic soils apply at 55-150 lb/acre at time of establishment or 40-100 lb/acre for established stands. |
| Sulphur (S) | Apply sulphate sulphur at 30 lb/acre on well-drained soils and grey luvisol (grey wooded) soils. Sulphur deficiency may occur in many soils and in any area of the province. A soil test is recommended to determine the available sulphur status of fields. |
Micronutrients
The micronutrient boron is particularly important for alfalfa. Visual deficiencies appear as yellowing to reddening of the youngest upper leaves on the plant. Deficiencies are generally limited to high pH, sandy soils when plants are under drought stress. Since deficiencies are often weather-related, they may be observed one year and not the next. Confirm deficiencies with soil and plant-tissue analysis. Where boron-deficiency is confirmed, broadcast apply 1-2 lb boron/acre. Apply with caution, since excessive boron can cause toxicity in following crops such as oats and beans.
Fertilizing mixtures of grasses and legumes
Stands that are more than 50% legume do not require nitrogen fertilizers. For stands that are less than 30% legume, responses to nitrogen fertilizer can be expected as for a pure grass stand. Where conditions permit, it is generally more profitable to re-seed mixtures containing legumes.