Several forage grasses and grass mixtures have adapted to Minnesota. As with other crops, you need adequate fertilizer programs 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. Therefore, the previous crop is not a consideration when making fertilizer guidelines.
We base nitrogen fertilizer guidelines on the expected yield. The expected yield will vary with such factors as intended use, management intensity and soil texture.
Nitrogen guidelines for grasses and grass mixtures in Minnesota
| Expected yield | N to apply |
|---|---|
| 2 tons of dry matter per acre | 60 lbs. per acre |
| 3 tons of dry matter per acre | 90 lbs. per acre |
| 4 tons of dry matter per acre | 120 lbs. per acre |
| 5+ tons of dry matter per acre | 150 lbs. per acre |
Factors influencing yield
You can expect yields of 4 or more tons of dry matter per acre under certain conditions. These include soils with good water holding capacity and intensive management practices, like rotational grazing.
Without irrigation, you can expect yields of 2 tons per acre when grasses are grown on sandy soils where moisture is usually limited.
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.
Application timing
The time of nitrogen fertilizer application should match the growth pattern of the forage grasses. With cool-season grasses, the majority of the growth takes place in late spring and early summer. Therefore, we suggest early spring application of nitrogen for these grasses. Brome-grass, orchardgrass and reed canarygrass are three major cool-season grasses grown in Minnesota.
Timing for warm-season grasses should be different. These grasses thrive when temperatures are warm in mid-summer. Therefore, we suggest a late spring application of nitrogen. Switchgrass is an example of a warm-season grass.
For situations with expected yields above 4 ton per acre, you can split apply of nitrogen fertilizer. If split application is an option, apply 3/4 of the nitrogen in early spring and 1/4 in late August.
The listed rates are for all forage grasses and grass mixtures. Broadcast fertilizer to established stands in early spring for cool-season grasses, and late spring for the warm season grasses.
Use one of the following equations if you want a phosphate guideline for a specific soil test and a specific expected yield.
- Recommended P2O5 = [19.12 - 0.723) (Bray P in ppm)] (Expected yield)
- Recommended P2O5 = [19.12 - (1.012) (Olsen P in ppm)] (Expected yield)
Phosphate fertilizer guidelines for grasses and grass mixtures
| Expected yield | P soil test: 0-5 parts per million (ppm) Bray and 0-3 ppm Olsen | P soil test: 6-10 ppm Bray and 4-7 ppm Olsen | P soil test: 11-15 ppm Bray and 8-11 ppm Olsen | P soil test: 16-20 ppm Bray and 12-15 ppm Olsen | P soil test: 21+ ppm Bray and 16+ ppm Olsen |
|---|---|---|---|---|---|
| 2 tons per acre | 40 lbs. of P2O5 per acre | 30 lbs. of P2O5 per acre | 20 lbs. of P2O5 per acre | 10 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre |
| 3 tons per acre | 50 lbs. of P2O5 per acre | 40 lbs. of P2O5 per acre | 30 lbs. of P2O5 per acre | 20 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre |
| 4 tons per acre | 60 lbs. of P2O5 per acre | 50 lbs. of P2O5 per acre | 40 lbs. of P2O5 per acre | 30 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre |
| 5+ tons per acre | 70 lbs. of P2O5 per acre | 60 lbs. of P2O5 per acre | 50 lbs. of P2O5 per acre | 40 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre |
Use the following equation if a potash guideline for a specific soil test and a specific expected yield is desired.
- Recommended K2O = [40.43 - (0.286) (Soil test K in ppm)] (Expected yield)
Potash fertilizer guidelines for grasses and grass mixtures
| Expected yield | K soil test: 0-40 ppm | K soil test: 40-80 ppm | K soil test: 80-120 ppm | K soil test: 120-160 ppm | K soil test: 160+ ppm |
|---|---|---|---|---|---|
| 2 tons per acre | 90 lbs. of K2O per acre | 60 lbs. of K2O per acre | 30 lbs. of K2O per acre | 0 lbs. of K2O per acre | 0 lbs. of K2O per acre |
| 3 tons per acre | 100 lbs. of K2O per acre | 70 lbs. of K2O per acre | 40 lbs. of K2O per acre | 10 lbs. of K2O per acre | 0 lbs. of K2O per acre |
| 4 tons per acre | 110 lbs. of K2O per acre | 80 lbs. of K2O per acre | 50 lbs. of K2O per acre | 20 lbs. of K2O per acre | 0 lbs. of K2O per acre |
| 5+ tons per acre | 120 lbs. of K2O per acre | 90 lbs. of K2O per acre | 60 lbs. of K2O per acre | 30 lbs. of K2O per acre | 0 lbs. of K2O per acre |
Research trials in Minnesota have shown that forage grasses and grass mixtures have not responded to the application to other nutrients in a fertilizer program. Therefore, none are suggested.
Reviewed in 2018