Grassland Fertilizer Calculator
Calculate seasonal nitrogen, phosphorus, and potassium requirements for grazing, silage, and hay
Work in progress — this calculator is still under development and may not be fully accurate. Use results as a guide only.
Grassland use
Base N rate: 50 kg N/ha per round
Soil indices
From a soil analysis report (index 0 = low, 3 = high)
Nitrogen supply from soil organic matter
Phosphorus status from soil test
Potassium status from soil test
Field area & fertiliser prices
24.71 acres
Season total nitrogen requirement
200kg N/ha
2000 kg N for 10.00 ha
Total N
200
kg N/ha
2000 kg total
P₂O₅
40
kg P₂O₅/ha
400 kg total
K₂O
160
kg K₂O/ha
1600 kg total
Per-round breakdown
| Round | N (kg/ha) | P₂O₅ (kg/ha) | K₂O (kg/ha) |
|---|---|---|---|
| Round 1 | 50 | 10 | 40 |
| Round 2 | 50 | 10 | 40 |
| Round 3 | 50 | 10 | 40 |
| Round 4 | 50 | 10 | 40 |
| Season total | 200 | 40 | 160 |
Estimated fertiliser cost
Based on nutrient content, not product quantities — check bag labels for actual nutrient %.
About these figures: Nitrogen requirements based on AHDB RB209 grassland guidance. N index 2 reduces requirement by 25 kg N/ha; index 3+ by 50 kg N/ha. P and K are maintenance targets for soil index 2, with build-up (+10–20 kg/ha) for lower indices and run-down (−10 kg/ha) for index 3. Always deduct nutrients from organic manure applications before ordering bagged fertiliser. Tissue and soil testing is recommended for accurate planning.