To apply a target nutrient rate (lbs of N per acre), back out the product needed from its analysis (the N-P-K percentages). Pounds of nutrient over the nutrient fraction gives pounds of product.
The example
150 lb N/ac, urea is 46% N.
| A | B | |
|---|---|---|
| 1 | Item | Value |
| 2 | 150 / 0.46 | — |
| 3 | Urea/acre | → 326 lb |
The formula
The formula:
How it works
How it works:
- Read the analysis — urea is 46-0-0, so 46% N by weight.
- Divide the target nutrient pounds by the fraction (0.46) for pounds of product per acre.
- Multiply by acres for the total, then by price for cost.
- For blends, solve each nutrient (N, P, K) separately and reconcile the product mix.
The analysis is a percentage of nutrient, not product. “Apply 150 lbs of nitrogen” does not mean 150 lbs of urea — urea is only 46% N, so you need 326 lbs of the bag to deliver 150 lbs of actual N. Forgetting to divide by the analysis under-applies by more than half. Always work from the nutrient target back to product through the analysis fraction.
Try it: interactive demo
Target N (lb/ac) and product %N.
Variations
Total product
Per acre × acres:
In tons
Bulk order:
Cost per acre
Product × price:
Pitfalls & errors
Divide by the analysis. Product needed = nutrient ÷ %fraction, not the nutrient target itself.
Percent as decimal. 46% is 0.46 in the divisor.
Each nutrient. Solve N, P, K separately for blends.
Practice workbook
Frequently asked questions
How do I calculate fertilizer rate in Excel?
Why divide by the analysis?
How do I handle a blend?
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