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Copy link Herb-Rich Grassland Trial with Polysulphate
Increased protein yield
Randwijk, Netherlands 2024
Increased protein yield
Key Conclusions
Herb-rich grassland requires less nitrogen fertilization than common grassland, but it is crucial to supply the soil properly with sulfur and potassium.
Key findings:
- Higher potassium application for the first and second cuts significantly increases yields.
- Mineral potassium fertilization is needed in poor soil conditions.
- Sulfur fertilization should be done early in the season, especially for the first two cuts.
Objective
Herb-rich grassland is becoming increasingly popular because it can be fertilized with less nitrogen than conventional grassland. However, proper fertilization with potassium, sulfur and calcium is important for high yields. In 2024, ICL conducted a trial on two-year-old herb-rich grassland on clay soil. Two levels of fertilization were tested. A total of six cuts were harvested.
Trial Details
Trial station
Randwijk, Netherlands
Assessments
Added value of potassium and sulfur fertilization in grass
Treatments
Trial design
The trial was conducted with three fertilization strategies, applying different amounts of potassium and sulfur. Following fertilizers were used:
- Cattle manure: 3.6 kg/ton nitrogen (N), 5.3 kg/ton K₂O, 1.75 kg/ton SO₃.
- Polysulphate: 14% K₂O, 6% magnesium (MgO), 17% calcium (CaO), 48% SO₃.
- ICL PotashpluS: 37% K₂O, 2% MgO, 7% CaO, 20% SO₃.
Soil test results and fertilization recommendations
| N soil content (kg/ha) | N advice (kg/ha) | S soil content (kg/ha) | SO₃ advice (kg/ha) | K plant available (kg/ha) | K₂O advice (kg/ha) |
|---|---|---|---|---|---|
| 135 | 80 | 8 | 72 | 170 | 490 |
Fertilization treatments
| Treatment | 1ˢᵗ cut | 2ⁿᵈ cut | 3ʳᵈ cut | 4ᵗʰ, 5ᵗʰ and 6ᵗʰ cuts | K₂O (kg/ha) | mineral SO₃ (kg/ha) | organic SO₃ (kg/ha) |
|---|---|---|---|---|---|---|---|
| Grower practice | 20 t/ha manure + 60 kg/ha NS 38-18 | 20 t/ha manure + 100 kg/ha NS 24-10 | 20 t/ha manure | - | 318 | 21 | 105 |
| Polysulphate | 20 t/ha manure + 60 kg/ha NS 38-18 + 165 kg/ha Polysulphate | 20 t/ha manure + 100 kg/ha NS 24-10 | 20 t/ha manure | - | 341 | 100 | 105 |
| ICL PotashpluS | 20 t/ha manure + 60 kg/ha NS 38-18 + 165 kg/ha ICL PotashpluS | 20 t/ha manure + 100 kg/ha NS 24-10 + 165 kg/ha ICL PotashpluS | 20 t/ha manure | - | 440 | 111 | 105 |
Treatments
Trial design
The trial was conducted with three fertilization strategies, applying different amounts of potassium and sulfur. Following fertilizers were used:
- Cattle manure: 3.6 kg/ton nitrogen (N), 5.3 kg/ton K₂O, 1.75 kg/ton SO₃.
- Polysulphate: 14% K₂O, 6% magnesium (MgO), 17% calcium (CaO), 48% SO₃.
- ICL PotashpluS: 37% K₂O, 2% MgO, 7% CaO, 20% SO₃.
Soil test results and fertilization recommendations
| N soil content (kg/ha) | N advice (kg/ha) | S soil content (kg/ha) | SO₃ advice (kg/ha) | K plant available (kg/ha) | K₂O advice (kg/ha) |
|---|---|---|---|---|---|
| 135 | 80 | 8 | 72 | 170 | 490 |
Fertilization treatments
| Treatment | 1ˢᵗ cut | 2ⁿᵈ cut | 3ʳᵈ cut | 4ᵗʰ, 5ᵗʰ and 6ᵗʰ cuts | K₂O (kg/ha) | mineral SO₃ (kg/ha) | organic SO₃ (kg/ha) |
|---|---|---|---|---|---|---|---|
| Grower practice | 20 t/ha manure + 60 kg/ha NS 38-18 | 20 t/ha manure + 100 kg/ha NS 24-10 | 20 t/ha manure | - | 318 | 21 | 105 |
| Polysulphate | 20 t/ha manure + 60 kg/ha NS 38-18 + 165 kg/ha Polysulphate | 20 t/ha manure + 100 kg/ha NS 24-10 | 20 t/ha manure | - | 341 | 100 | 105 |
| ICL PotashpluS | 20 t/ha manure + 60 kg/ha NS 38-18 + 165 kg/ha ICL PotashpluS | 20 t/ha manure + 100 kg/ha NS 24-10 + 165 kg/ha ICL PotashpluS | 20 t/ha manure | - | 440 | 111 | 105 |
Results
Fertilization with ICL PotashpluS produced the highest dry matter and protein yields. Over six cuts, ICL PotashpluS provided:
- 2205 kg/ha more dry matter yield
- 334 kg/ha more protein yield
The higher yield in the first cut was due to the combination of higher potassium and sulfur inputs (see graphs below).
Comparison with Polysulphate
- For the first cut, the treatment with ICL PotashpluS received less sulfur (46 kg/ha SO₃) but more potassium (38 kg/ha K₂O) than the Polysulphate treatment.
- Also in cuts 2 through 6, ICL PotashpluS delivered higher yields due to structurally better potassium fertilization (see Table 3).
Potassium fertilization
For the field, the potassium recommendation was 490 kg/ha K₂O. For the trial plot, only the crop-specific advice of 105 kg/ha K₂O for the first cut was followed, applied in manure. ICL PotashpluS added an additional 62 kg/ha of potassium to this, which was already half of the required repair dose.
In the second cut, the ICL PotashpluS treatment received 61 kg/ha more potassium than the other objects, resulting in higher yields in the remaining cuts.
Advice
- Nitrogen fertilization: Follow the fertilization recommendation for grass clover.
- Sulfur fertilization: Fertilize with 100 kg/ha SO₃ for the first two cuts.
- Potassium fertilization: Use about 40 kg/ha of K₂O per ton of dry matter.
Fertilization options:
- In February, use 200 kg/ha Polysulphate, or
- Select 500 kg/ha of ICL PotashpluS spread over the first two cuts.
ICL PotashpluS combines sulfur and potassium in one product, providing more efficient fertilization (see Table 4 and Table 5). With the right balance of potassium and sulfur, optimal yields of herb-rich grassland are achieved.
| Potassium in soil situation | 1st cut (February) | 1st cut (March) | 2nd cut |
|---|---|---|---|
| good | manure + Polysulphate | N-fertilizer | manure |
| good | manure | blend N+Polysulphate | manure |
| (relatively) low | manure + PotashpluS | N-fertilizer | manure+PotashpluS |
| (relatively) low | manure | Blend N+PotashpluS | manure+PotashpluS |
