In short
- A horse pasture fertilizer calculator turns your acres, grass and fertilizer analysis into pounds and bags of product a year, plus total lime if your soil lab gives a rate.
- UF/IFAS bahiagrass options: 50 to 60, 100 or 160 lb of nitrogen per acre a year; grazed bermudagrass: 160. Target soil pH is 5.5.
- Phosphate and potash depend on your soil test, so many pastures need none. The calculator shows when a blend gives too much.
- Quantities only, with no prices. A pasture contractor or your feed store quotes the work.
On this page
- How the fertilizer is worked out
- UF/IFAS grazing rates by option
- Pounds of product per acre for a nitrogen rate
- Bags of 16-4-8 per year by acres
- Notes for an Ocala pasture
- What this calculator does not cover
- Questions to ask a pasture contractor
- Next step: get a written quote
- Sources
- Frequently asked questions
This horse pasture fertilizer calculator is for Ocala and Marion County owners who graze bahiagrass or bermudagrass. It sits beside our seed rate calculator (planting), the acres per horse calculator (how much land) and the rotation calculator (how to split it); this one answers how much fertilizer and lime to buy.
En español: calculadora de fertilizante y cal para pasto de caballos
| Your numbers | Result |
|---|
Example: 6 acres of bahiagrass at the medium N option, with a 16-4-8 blend in 50-lb bags, soil low in phosphorus and potassium. Rates are UF/IFAS published figures.
How the fertilizer is worked out
- Area.
Acres, or length x width in feet divided by 43,560. 6 acres is 261,360 square feet.
- Nitrogen target.
The UF/IFAS yearly rate for your option. Medium is 100 lb of N per acre.
- Product.
N target divided by the N percent as a decimal. 100 / 0.16 = 625 lb of 16-4-8 per acre.
- All acres.
Product per acre x acres: 625 x 6 = 3,750 lb. Bags = pounds divided by bag size, rounded up: 3,750 / 50 = 75.
- Check phosphate and potash.
Product x P2O5 percent: 625 x 0.04 = 25 lb of P2O5, and 625 x 0.08 = 50 lb of K2O, compared with the soil-test targets.
- Lime.
Lab tons per acre x acres, at 2,000 lb a ton.
UF/IFAS grazing rates by option
| Option | N lb/acre/year | P2O5 if P low | K2O if K low |
|---|---|---|---|
| Bahiagrass, low N | 50 to 60 | 25* | 0 |
| Bahiagrass, medium N | 100 | 25* | 50 |
| Bahiagrass, high N | 160 | 40* | 80 |
| Bermudagrass, grazed | 160 | 40 | 80 |
*Bahiagrass: phosphate only if tissue phosphorus is also under 0.15 percent. Potash for a Medium soil test is 0 (medium N) or 40 lb (high N and bermudagrass); none for High. Phosphate is none for Medium or High phosphorus.
Pounds of product per acre for a nitrogen rate
| Product (N-P-K) | 50 lb N | 100 lb N | 160 lb N |
|---|---|---|---|
| 16-4-8 | 313 | 625 | 1,000 |
| 10-10-10 | 500 | 1,000 | 1,600 |
| 34-0-0 | 147 | 294 | 471 |
| 46-0-0 | 109 | 217 | 348 |
| 21-0-0 | 238 | 476 | 762 |
Arithmetic: N rate / N percent, rounded to the nearest pound. 10-10-10 also puts on as much P2O5 and K2O as N, far more than the soil-test targets above.
Watch out: a 10-10-10 bag at 100 lb of nitrogen puts on 100 lb of P2O5, four times the 25 lb UF/IFAS lists for a low-phosphorus soil. Check the soil test first, then pick the bag.
Bags of 16-4-8 per year by acres
| Acres | Low N: bags | Medium N: bags | High N: bags |
|---|---|---|---|
| 1 | 7 to 8 | 13 | 20 |
| 2 | 13 to 15 | 25 | 40 |
| 5 | 32 to 38 | 63 | 100 |
| 10 | 63 to 75 | 125 | 200 |
| 20 | 125 to 150 | 250 | 400 |
50-lb bags rounded up, 16-4-8 blend, nitrogen only (phosphate and potash from the blend not matched to a soil test).
Notes for an Ocala pasture
- Soil test first. UF/IFAS notes that sandy soils need less lime, and the change is short-lived. Your county extension office can tell you how to submit a soil sample and a forage tissue sample to the UF/IFAS lab.
- Timing. Nitrogen in early spring; a second dose in early summer for the medium and high options. No fertilizer after mid-August for hay fields, per UF/IFAS.
- Spreader. Ask whoever spreads for a calibrated spreader and the pounds per acre they will put down, so you can compare to this page.
- Water. Marion County sits over springs. Keep fertilizer off wet ground and away from ditches and springs; ask the extension office about local rules.
What this calculator does not cover
- Price. No prices here. See horse barn cost in Ocala and the cost calculator.
- Hay fields. Hay takes more: 80 lb of N in spring and again after each cutting. Not modeled here.
- New plantings. Establishment uses 30 lb of N after emergence and 70 lb a month or so later. See the seed rate calculator for planting.
- Manure and compost. They supply nutrients too; see horse manure management in Marion County.
Questions to ask a pasture contractor
- Has the soil been tested? Ask for the pH, phosphorus and potassium results and the lime recommendation.
- What analysis and how many pounds per acre? Compare to your result above.
- When will lime go on? UF/IFAS says 3 to 6 months before fertilizer.
- Is spreading in the quote? Use the quote comparison worksheet.
Next step: get a written quote
This tool estimates quantities, not the price or the job. We are a referral service, not a contractor; we connect visitors with independent local providers. Use the form below to ask independent local builders for a written quote, and read how to choose a horse barn builder first. To compare bids side by side, use the bid comparison calculator.
Sources
- UF/IFAS SL129, Standardized Fertilization Recommendations for Agronomic Crops: Table 2 and footnotes 126 and 131 (bermudagrass and bahiagrass N, P2O5, K2O, lime and pH target 5.5). Archival 2007 copy.
- UF/IFAS SS-AGR-332, Bahiagrass (Paspalum notatum): Overview and Management: fertilizer and liming for grazed pastures; phosphate with tissue test; lime 3 to 6 months ahead.
- UF/IFAS SL249, Getting the Most out of Bahiagrass Fertilization: Table 5 spring recommendations; liming when pH is 5.3 or lower; lime reaching only 2 to 3 inches.
- UF/IFAS SS-AGR-60, Bermudagrass Production in Florida: pH 5.5 to 6.0; 80 lb N for grazing; ammonium sulfate lowers pH.
Frequently asked questions
How much nitrogen does a horse pasture need per year in Florida?
UF/IFAS gives three grazing options for bahiagrass: about 50 to 60 lb of nitrogen per acre in early spring (low), 100 lb (medium) and 160 lb split into two 80-lb applications (high). For grazed bermudagrass, SL129 says 80 lb in early spring and 80 lb at mid-season. Nitrogen is not set by a soil test; it follows how hard you want the pasture to work.
Do I need phosphorus and potassium?
Only if the soil test says so. UF/IFAS gives phosphate (P2O5) and potash (K2O) amounts for very low and low soils and says that for medium and high phosphorus neither a phosphorus application nor a tissue test is recommended on bahiagrass. For bahiagrass, UF/IFAS also asks for a forage tissue test: apply phosphate only if the soil is low and tissue phosphorus is under 0.15 percent.
How much lime does my pasture need?
UF/IFAS publishes the target, not a tons-per-acre table. The target pH is 5.5 for bahiagrass and bermudagrass, and a lime requirement is calculated only when the tested pH is at least 0.2 units below the target (5.3 or lower). The tons per acre come from the lab's lime requirement test on your sample, which is why this page asks for that number instead of guessing.
When should I apply lime and fertilizer?
UF/IFAS says to apply lime at least 3 to 6 months before fertilizing so it can react, and to retest pH every 2 to 3 years. Nitrogen goes on in early spring for bahiagrass, with a second application in early summer for the medium and high options. Without mowing the lime in, UF/IFAS notes it rarely moves more than 2 to 3 inches into the soil in a year or two.
Why does my 10-10-10 bag give too much phosphorus?
Because the blend is built around equal parts, not around what the pasture needs. At 100 lb of nitrogen, a 10-10-10 product also puts on 100 lb of P2O5, four times the 25 lb UF/IFAS lists for a low-phosphorus soil and more than the none it lists for medium or high. A blend with a low or zero middle number, or a straight nitrogen product, fits most pastures better. Ask your extension office.