Quick facts
- Several forage grasses and grass mixtures are adapted to Minnesota.
- Adequate fertilizer programs are needed for optimum economic production.
- This is true for grasses grown for either hay or pasture.
- Grasses and grass mixtures, whether grown for hay or pasture, are perennial crops, so previous crops are not a consideration when making fertilizer guidelines.
Nitrogen guidelines
Nitrogen fertilizer guidelines are based on expected yield. The expected yield will vary with such factors as intended use, management intensity and soil texture.
The recommendations for expected yields should not be used for situations where a legume is grown in combination with grass. Separate guidelines are available for grass-legume mixtures.
Expected yields of 4 or more tons of dry matter per acre are reasonable where soils have good water-holding capacity and intensive management practices such as the use of rotational grazing are used.
Without irrigation, expected yields of 2 tons per acre are more reasonable when grasses are grown in sandy soils where moisture is usually limited.
Timing
It’s not possible to assign a yield expectation for every situation in Minnesota where forage crops are grown. This is a decision for the individual managing the production of forage grasses.
The time of nitrogen fertilizer application should match the growth pattern of the forage grasses. With cool season grasses, most of the growth takes place in late spring and early summer. Early spring application of nitrogen is suggested for these grasses. Brome grass, orchard grass and reed canary grass are three major cool season grasses grown in Minnesota.
The timing for warm season grasses should be different. These grasses thrive when temperatures are warm in mid-summer. So, a late spring application of nitrogen is suggested. Switchgrass is an example of a warm season grass.
Split application of nitrogen fertilizer is an option for intensive management situations when expected yields are greater than 4 tons per acre. If the split application is an option, 3/4 of the nitrogen should be applied in early spring and 1/4 in late August.
Nitrogen recommendations for grasses for hay and pastures
| Expected yield | N to apply |
|---|---|
| 2 tons dry matter/acre | 60 lb./acre |
| 3 tons | 90 |
| 4 tons | 120 |
| 4+ tons | 150 |
Phosphorus and potash guidelines
The listed rates for phosphate fertilizer and potash fertilizer are for all forage grasses and grass mixtures.
The needed fertilizer should be broadcast to established stands in early spring for cool season grasses, and late spring for warm season grasses.
Phosphate fertilizer guidelines (pounds of P2O5 suggested to apply per acre) for grasses for hay and pasture production are based on either the Bray-P1 or Olsen soil methods test reported in parts per million (ppm). Use one of the following equations if you want a P2O5 recommendation for a specific yield goal:
- P2O5 Rec = [19.12-(.723)(Bray P, ppm)] (Yield goal)
- P2O5 Rec = [19.12-(1.012)(Olsen P, ppm)] (Yield goal)
Phosphate fertilizer guidelines
| Expected Yield Bray-P1 Expected Yield Olsen |
0-5 ppm 0-3 ppm |
6-10 ppm 4-7 ppm |
11-15 ppm 8-11 ppm |
16-20 ppm 12-15 ppm |
21+ ppm 16+ ppm |
|---|---|---|---|---|---|
| 2 tons/acre | 40 lb./acre | 30 lb./acre | 20 lb./acre | 10 lb./acre | 0 lb./acre |
| 3 tons/acre | 50 | 40 | 30 | 20 | 0 |
| 4 tons/acre | 60 | 50 | 40 | 30 | 0 |
| 4+ tons/acre | 70 | 60 | 50 | 40 | 0 |
Potash fertilizer guidelines (pounds of K2O suggested to apply per acre) for hay and pastures production are based on the ammonium acetate potassium (K) test reported in parts per million (ppm). Use the following equation if you want a K2O recommendation for a specific soil test value and a specific yield goal:
- K2O Rec = [40.43-(.0286)(K soil test, ppm)] (Expected yield goal).
Potash fertilizer guidelines
| Expected Yield | K: 0-40 ppm | K: 41-80 ppm | K: 81-120 ppm | K:121-160 ppm | K: 161+ ppm |
|---|---|---|---|---|---|
| 2 tons/acre | 90 lb./acre | 60 lb./acre | 30 lb./acre | 0 lb./acre | 0 lb./acre |
| 3 tons/acre | 100 | 70 | 40 | 10 | 0 |
| 4 tons/acre | 110 | 80 | 50 | 20 | 0 |
| 4+ tons/acre | 120 | 90 | 60 | 30 | 0 |
Other nutrient needs
Research trials in Minnesota have shown that forage grasses and grass mixtures have not responded to the application of other nutrients in a fertilizer program. Therefore, none are suggested.
Reviewed in 2023