Seeds and fertilisers
Work out the seeding rate from the plants you want and the seed lot, and the units of N, P₂O₅ and K₂O your fertilisers supply.
Unit arithmetic, not a fertiliser recommendation
Nutrient needs depend on the soil, the crop and the rules in your area: check them with your adviser.
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Calculation version:agri-inputs@1.0.0.
How to use it
- 1Seeding rate: enter the plants per m² you want, the thousand-seed weight and germination from the label, and the field emergence you expect.
- 2Fertilisers: enter the units the crop needs (from your soil analysis or adviser) and the fertilisers with their content, rate and price.
How it calculates
- Seeds per m² = target plants / (germination × emergence). kg/ha = seeds per m² × 10,000 × thousand-seed weight (g) / 1,000,000.
- Units supplied by a fertiliser = rate (kg/ha) × content (%) / 100, for N, P₂O₅ and K₂O. Cost = rate × price per tonne / 1,000.
Verifiable example
With the example values (300 plants per m², 45 g thousand-seed weight, 95% germination and 85% emergence) you need 372 seeds per m², about 167 kg/ha. With 300 kg/ha of an 8-15-15 and 200 kg/ha of 46% urea, 116 units of N, 45 of P₂O₅ and 45 of K₂O are supplied, for €246/ha.
Limitations
- It isn't a fertiliser recommendation: needs depend on the soil, the crop, the expected yield and the rules (for example, in nitrate vulnerable zones).
- It doesn't take into account losses or the efficiency of each form of nitrogen.