Fertilization Guidelines

What is Soil Fertility?

Soil fertility refers to the ability of a soil to sustain plant growth by providing essential plant nutrients and favorable chemical, physical, and biological characteristics as a habitat for plant growth. Soil fertility affects yield, carrying capacity, persistence, resistance to stress, forage nutritive value, and many other aspects of the production system. Failing to properly provide nutrients to the plants via the soil will result in poor economic returns for pasture-based livestock enterprise. Livestock producers often do not appreciate how important this connection is to the overall profitability of their operation.

This page provides practical recommendations for fertilizing established pastures and hayfields in Georgia. For deeper understanding of soil fertility and plant nutrition, please review B1346 Soil and Fertilizer Management Considerations for Forage Systems in Georgia.

Overview of Soil Fertility in Forage Systems
Soil pH
Fertility Recommendations

Overview of Soil Fertility in Forage Systems

There are 16 essential nutrients for plant growth. Forage production will be reduced if their availability is limited. Although most forages will persist in low-fertility soils, a good lime and fertility program is essential to the production of good forage yield and to economic returns when used in livestock operations. A balanced fertility program is critical to stand longevity and economical sustainability of forage-based production systems.

Fertilizer Sources

There are many different fertilizer sources available in Georgia. The table below has the most common sources used for forage production across the state. If you encounter a fertilizer source not on the list below, consult with your local County Extension Agent on its potential use in your system before purchasing the material. There are many by-product or alternative fertilizer or lime sources marketed for forage production. Most sources have not been tested by University researchers and are not recommended for use in Georgia until the testing is complete.

Animal manures (including broiler litter) are highly variable in their nutrient concentration and should always be tested before they are applied. Poultry litter may be tested for free at the University of Georgia Feed and Environmental Water Lab.

Common fertilizer sources available in Georgia and their impact on soil pH.

Fertilizer	N-P₂O₅-K₂O	Effect on soil pH¹
Ammonium nitrate	34-0-0	↓↓
Ammonium sulfate	21-0-0	↓↓↓↓
UAN	28 to 32-0-0	↓↓
Urea	46-0-0	↓↓
Urea (sulfur coated)	38-0-0	↓↓↓
Broiler litter	3-2-2	↑
Cattle manure	1.5-1.5-1.2	↓
Monoammonium phosphate	11-48-0	↓↓↓↓
Diammonium phosphate	18-46-0	↓↓↓
Triple superphosphate	0-46-0	none
Muriate of potash	0-0-60	none

1 Arrows pointing upward indicate positive change or increase of soil pH. Arrows pointing downward indicate negative change or decrease of soil pH. Multiple arrows indicate more intense response or bigger change in soil pH.

Other Macro and Micronutrients

Other nutrients required for plant growth include calcium (Ca), magnesium (Mg), Sulfur (S), Chlorine (Cl), Iron (Fe), Boron (B), Manganese (Mn), Zinc (Zn), Copper (Cu), and Molybdenum (Mo). These macro- and micronutrients are rarely limiting in grass pastures or hayfields, so application of these nutrients are made on a case-by-case basis. If a nutrient deficiency is suspected, please contact your local County Extension Agent for assistance with plant tissue testing.

Soil Testing

Since forage can only be as productive as the most limiting input, it is important to make fertilizer decisions based on reports from a soil test. Pastures should be sampled every three years while hayfields need to be sampled annually. Harvesting forage removes significantly more nutrients from the soil than grazing, so these acres must be sampled more frequently. Work with your local County Extension Agent to learn more about soil testing procedures for your farm.

Soil pH

Soil pH affects many soil properties including nutrient availability, soil structure, soil biological activity, and potential for aluminum toxicity. Many soils in Georgia are acidic (low pH; below 6.0), but it is possible for soils to be too basic (high pH; above 7.0). Ideally the soil pH should be between 6.0 and 7.0.

Lime Sources

Both dolomitic and calcitic (Hi-Cal) lime are recommended for use in Georgia. Many local fertilizer distributors will call these “ag limes” or “agricultural limes”. Dolomitic lime contains both calcium and magnesium whereas calcitic lime only contains calcium.

There are many alternative lime products available for purchase. These may include such as wood ash, marl, basic slag, eggshells, and other byproducts. Like animal manures, these products are highly variable and should be tested for their liming ability before application. Work with your local County Extension Agent to submit a sample to determine the calcium carbonate equivalent. This value will allow you to compare the liming ability of the product compared to an agricultural lime.

Calculating Use Rates of Alternative Lime Products

To calculate the quantity of the lime product needed compared to agricultural lime, use the following steps.

Convert the calcium carbonate equivalent from a percentage to a decimal. This is done by moving the decimal two places to the left. For instance, 75% would equal 0.75.
Enter the values into the following equation.

Fertility Recommendations

Tall Fescue Pasture Fertility Recommendations

Nitrogen: If grazing 2 cows/acre, apply 50 lbs N/acre/year; if grazing 1 cow/acre, apply 100 lbs N/acre/year. Nitrogen is usually applied in August-September if stockpiling forage for grazing.
Phosphorus: Apply up to 80 lbs P₂O₅/acre at any time during the year.
Potassium: Apply up to 80 lbs K₂O/acre/year. If possible, apply half in late February and in September.

Tall Fescue Combined Pasture and Hayfield Fertility Recommendations

Nitrogen: Apply 100 lbs N/acre/year, apply half in late February and in September.
Phosphorus: Apply up to 80 lbs P₂O₅/acre at any time during the year.
Potassium: Apply up to 80 lbs K₂O/acre/year. If possible, apply half in late February and in September.

Tall Fescue Combined Hayfield Fertility Recommendations

Nitrogen: If managing your field for 2 cuttings/year, apply 60-75 lbs N/acre in late February and in September. If managing for 3 cuttings/year, apply 60-75 lbs N/acre in late February, in May following first harvest, and in September following second harvest.
Phosphorus: Apply up to 80 lbs P₂O₅/acre at any time during the year.
Potassium: Apply up to 80 lbs K₂O/acre/year. If possible, apply half in late February and in September.

Hybrid Bermudagrass Pasture Fertility Recommendations

Nitrogen: For continuously grazed pastures apply 150-200 lbs N/acre; for intensively grazed pastures apply 200-250 lbs N/acre. Apply half of the N at green-up (April to May) and the other half in mid-summer (July).
Phosphorus: Apply up to 60 lbs P₂O₅/acre at any time during the year.
Potassium: Apply up to 120 lbs K₂O/acre/year. Apply half in the spring at green-up (April to May) and the other half in mid-summer (July to August).

Hybrid Bermudagrass Hayfield Fertility Recommendations

Nitrogen: Apply up to 80 lbs N/acre at green-up and following each harvest except the last.
Phosphorus: Apply up to 80 lbs P₂O₅/acre at any time during the year.
Potassium: Apply 250 lbs K₂O/acre/year. Apply half in the spring at green-up (April to May) and the other half following your next to last harvest (usually August).

Seeded Bermudagrass Pasture Fertility Recommendations

Nitrogen: For continuously grazed pastures apply 75-125 lbs N/acre; for intensively grazed pastures apply 125-175 lbs N/acre. Apply half of the N at green-up (April to May) and the other half in mid-summer (July to August).
Phosphorus: Apply up to 60 lbs P₂O₅/acre at any time during the year.
Potassium: Apply up to 80 lbs K₂O/acre/year. Apply half in the spring at green-up (April to May) and the other half in mid-summer (July to August).

Seeded Bermudagrass Hayfield Fertility Recommendations

There are no official university recommendations to date on seeded bermudagrass hay. Below is general guidance to build a fertility program for seeded bermudagrass hay production.

Nitrogen: Apply up to 50 lbs N/acre at green-up and following each harvest except the last.
Phosphorus: Apply up to 80 lbs P₂O₅/acre at any time during the year.
Potassium: Apply 125 lbs K₂O/acre. Apply half in the spring at green-up (April to May) and the other half following your next to last harvest (usually August).

Bahiagrass Pasture Fertility Recommendations

Nitrogen: For continuously grazed pastures apply 75-125 lbs N/acre; for intensively grazed pastures apply 125-175 lbs N/acre. Apply half of the N at green-up and the other half in mid-summer.
Phosphorus: Apply up to 80 lbs P₂O₅/acre at any time during the year.
Potassium: Apply up to 80 lbs K₂O/acre/year. Apply half in the spring at green-up (April to May) and the other half in mid-summer (July to August).

Bahiagrass Hayfield Fertility Recommendations

There are no official university recommendations to date on bahiagrass hay. Below is general guidance to build a fertility program for bahiagrass hay production.

Nitrogen: Apply 50 lbs N/acre at green-up and following each harvest except the last.
Phosphorus: Apply up to 80 lbs P₂O₅/acre at any time during the year.
Potassium: Apply 100 lbs K₂O/acre/year. Apply half in the spring at green-up (April to May) and the other half following your next to last harvest (usually August).

Warm Season Annual Pastures

Nitrogen: Apply 40 to 60 lbs N/acre soon after forage emerges. Apply additional applications of 50 to 60 lbs N/acre for each month during the summer grazing season.
Phosphorus: Apply based on soil test recommendations soon after emergence.
Potassium: Apply based on soil test recommendations soon after emergence.

Warm Season Annual Hayfields or Baleage Fields

Nitrogen: Apply 40 N/acre at planting and 60 lbs N/acre soon after forage emerges. Apply additional applications of 60 lbs N/acre after each harvest except the last.
Phosphorus: Apply based on soil test recommendations soon after emergence. If more than one harvested is anticipated, increase the amount on your soil test recommendation by 25%.
Potassium: Apply based on soil test recommendations soon after emergence. If more than one harvested is anticipated, increase the amount on your soil test recommendation by 25%.

Cool Season Annual Forages

Nitrogen: Apply 40 to 50 lbs N/acre soon after grasses emerge and a second application of 40–50 pounds N per acre in mid-winter to increase winter and spring forage production. Ryegrass may require a third application of 40–50 lb N per acre in early spring since it lives longer than small grains. Annual legumes should only require one application of nitrogen to promote early growth before nitrogen fixation is initiated.
Phosphorus: Apply based on soil test recommendations soon after emergence.
Potassium: Apply based on soil test recommendations soon after emergence.