Fertilizer Calculator (NPK)
How much fertilizer product delivers your target pure nutrient per decare — urea, AN, CAN, DAP, compound NPK grades built in.
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Selected fertilizer has none of this nutrient
From Pure Nutrient to Product Bags
Recommendations come as pure nutrient (say, 8 kg N per decare) but bags contain a percentage: urea is 46% N, ammonium nitrate 33%, CAN 26%, DAP 18% N + 46% P₂O₅. Product needed = target ÷ (content ÷ 100) × area: 8 kg N/da from urea means 17.4 kg/da — over 10 decares, 174 kg, about seven 25-kg bags.
Compound fertilizers deliver several nutrients at once: 100 kg of 15-15-15 carries 15 kg each of N, P₂O₅ and K₂O. The calculator shows what the chosen product supplies of the other nutrients too, so you can see what DAP already covered before topping nitrogen up with urea. Soil analysis remains the honest basis for the target numbers.
Frequently Asked Questions
Why do recommendations use P₂O₅ and K₂O instead of P and K?
Convention from historic analysis methods — bags and advice worldwide state phosphorus as P₂O₅ (2.29× elemental P) and potassium as K₂O (1.2× K). Enter targets in the same oxide form and everything matches.
Can I convert between nitrogen fertilizers?
Yes, by N content: 100 kg urea (46 N) equals ~139 kg AN (33 N) or ~177 kg CAN (26 N) in nitrogen terms. Timing and volatilization differ — urea benefits from incorporation.
Is more fertilizer always more yield?
No — response flattens and then reverses (lodging, burn, leaching). Regional trial-based recommendations and soil tests define the economic optimum, which this tool helps you hit precisely.
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Fertilizer Calculator (NPK)