Food Plot Fertilizer Calculator
Enter the N, P₂O₅ and K₂O your soil test calls for and see how much of each product to spread.
Plot size to scale fertilizer for
Elemental conversion (if lab reports P & K instead of P₂O₅ & K₂O)
Fertilizer to buy
13-13-13: 230.8 lb, 0-46-0 (Triple Superphosphate): 65.2 lb, 0-0-60 (Muriate of Potash): 50.0 lb
| Nutrient | Needed | Supplied | Diff |
|---|---|---|---|
| N | 30.0 | 30.0 | 0.0 |
| P₂O₅ | 60.0 | 60.0 | 0.0 |
| K₂O | 60.0 | 60.0 | 0.0 |
Start from your soil-test lab's recommendations and your state extension's planting dates. Always follow product labels.
Pounds of product = pounds of nutrient needed ÷ the nutrient's percentage. 70 lb of P₂O₅ needs 70 ÷ 0.46 = 152 lb of 0-46-0 (Alabama Extension's example). A blend like 13-13-13 is usually set by one nutrient; use straight products to top up the rest instead of over-applying.
Worked example
30-60-60 with 13-13-13 + straights → 230.8 lb/acre 13-13-13 + 65.2 lb 0-46-0 + 50.0 lb 0-0-60. MSU's lawn example: 3 lb N per 1,000 sq ft with 13-13-13 → about 23 lb per 1,000 sq ft.
How it's calculated
Single product: Rate (lb/acre) = nutrient needed (lb/acre) ÷ (analysis percentage ÷ 100). For example, 70 lb of P₂O₅ using 0-46-0 requires 70 ÷ 0.46 = 152.2 lb/acre.
Blend + top-up: The base blend is applied at the maximum rate that does not exceed any of the three nutrient targets: blend rate = min(need ÷ blend %). The remaining unmet requirements are supplied by single-nutrient straight fertilizers (urea 46-0-0, triple superphosphate 0-46-0, or potash 0-0-60).
Oxide conversions: If the laboratory report gives elemental P and K, they are converted to oxide equivalents using standard conversion factors: P₂O₅ = P × 2.2914; K₂O = K × 1.2046.
Frequently Asked Questions (FAQ)
My report shows P and K, not P₂O₅ and K₂O
Multiply elemental P by 2.2914 to get P₂O₅, and elemental K by 1.2046 to get K₂O. The calculator includes an Elemental mode to convert these values automatically.
Why not just use more 13-13-13?
It over-applies nitrogen and costs more.
Do legumes need nitrogen?
If legumes make up more than 30 % of the stand, no extra nitrogen is needed (Alabama Extension).
Sources
- MSU Extension P3825 — Interpreting Your Soil Test Report for Homeowners
Product = nutrient ÷ percentage; N-based blend rates; 23 lb example
- Alabama Cooperative Extension — Soil Testing, Liming and Fertilizing Wildlife Food Plots
pH 6.0–6.5, lime timing, pelletized lime notes, legume 30 % rule, 0-46-0 example
Last reviewed: 2026-10-26
Built and maintained by Numberwright. The formulas come from university extension publications (Mississippi State, Clemson, Alabama Extension) and USDA NRCS, linked below. Found a mistake? Contact details coming soon.
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