How Numberwright Food Plot calculates
Numberwright Food Plot uses standard formulas from university agricultural extension services (Mississippi State University Extension, Clemson Cooperative Extension, Alabama Cooperative Extension) and the USDA Natural Resources Conservation Service (NRCS).
1. Plot Area Scaling
All seed, lime, and fertilizer requirements scale directly with plot acreage:Plot Amount = Per-Acre Rate × Plot Acres.
Plot acreage is determined by converting square feet: Acres = Square Feet ÷ 43,560. For triangular plots, Heron's formula calculates the exact area from the three measured side lengths:s = (a + b + c) ÷ 2, Area = √[s(s − a)(s − b)(s − c)].
2. Seed Mixes & Pure Live Seed (PLS)
Monoculture benchmark rates come from Mississippi State University Extension Publication M1591 ("Deer Food Plot Planting Guide for the Southeast"). When a seeding range is published, the calculator uses the midpoint.
In a species mix, each plant receives its percentage share of the pure stand rate:Species Target Rate = Monoculture Rate × (Share % ÷ 100). Total shares must equal 100 %.
To account for inert seed coating or seed tag lab results, Pure Live Seed is calculated per USDA NRCS:PLS % = (Germination % + Dormant %) × Purity % ÷ 100. The bulk seeding rate is then:Bulk Rate (lb/acre) = Target Rate ÷ (PLS % ÷ 100).
3. Lime Neutralizing Value (RNV) Adjustment
Most labs assume 100 % RNV; check your report. The product rate is adjusted for your lime's RNV.
When sieve analysis is available, RNV is computed per MSU Extension Publication P3762:RNV % = CCE % × [0.5 × (% pass 10-mesh − % pass 50-mesh) + % pass 50-mesh] ÷ 100.
The product rate to apply is:Product Rate (tons/acre) = Recommended Rate × (Lab Basis % ÷ Product RNV %). Total pounds required is Rate × 2,000 × Acres, and bags needed is ceil(Pounds ÷ Bag Size).
4. Fertilizer Balance: Blend + Straight Top-up
We calculate the maximum rate of base blend that does not exceed any of the three nutrient targets (N, P₂O₅, K₂O):Blend Rate = min(Need_i ÷ (Blend_i % ÷ 100)).
Remaining unmet nutrient deficits are topped up with straight single-nutrient fertilizers: Urea 46-0-0 for nitrogen, Triple Superphosphate 0-46-0 for phosphate, and potash 0-0-60 for potassium.
Elemental report conversions: P₂O₅ = P × 2.2914; K₂O = K × 1.2046.
5. Spreader Calibration
Calibrated according to Clemson Cooperative Extension HGIC 1657:Test Strip Area = Swath Width (ft) × Strip Length (ft).Measured Rate (lb/1,000 sq ft) = Applied Weight (lb) ÷ Test Strip Area × 1,000.Rate per Acre = Rate per 1,000 sq ft × 43.56. Within 10 % of target counts as a pass (the 10 % tolerance is our UI choice).
What we don't do
We don't calculate lime from buffer pH (labs use different methods) and we don't give state planting calendars yet.
Sources
- MSU Extension M1591 — Deer Food Plot Planting Guide for the Southeast
Species seeding rates (drill/broadcast), Southeast dates, notes
- MSU Extension P3762 — Agricultural Limestone's Neutralizing Value
RNV formula, rate adjustment, cost per effective ton, worked examples
- MSU Extension P3102 — Getting the Most Bang for Your Buck: Liming and Fertilizing Wildlife Food Plots
Pelletized vs bulk lime, $210 example, pH below 6.0, re-test at ≥ 4 tons
- 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
- USDA NRCS — Seed Quality (PLS)
PLS formula and worked example
- Clemson HGIC 1657 — Calibrating Spreaders
Test-strip method and example
- UGA Extension C798 — Calibration of Dry Broadcast Fertilizer Applicators (2024)
Further reading on spread patterns
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.