Ann Swinker, Extension Horse Specialist, Penn State University
A good fertilization program is necessary to produce high yields of quality forage and to maintain healthy stands of grasses and legumes. The rates and types of fertilizer required vary with different forage crops, management intensity and soil type. Soil testing is a valuable tool when developing a pasture fertilization program. Sample hay fields annually and sample grazed pastures at least every other year. Contact your county Extension office for more information on soil testing.
Soil pH is a measure of soil acidity. Most acidic soils require periodic liming to increase soil pH and supply calcium and magnesium. Availability of many nutrients necessary for plants decrease with low soil pH. Lime soils to maintain availability of these beneficial nutrients and decrease availability of other toxic elements like aluminum. Apply lime according to soil test recommendations.
When you purchase fertilizer materials, the analysis tag shows the quantity of nitrogen (N), phosphate (P2O5) and potash (K20) the bag contains. These values are given on a percentage basis. For example, a 5-10-15 fertilizer contains 5 percent nitrogen, 10 percent phosphate and 15 percent potash. If the fertilizer contains all three elements (N, P, and K), then it is considered a “complete” fertilizer. A pasture soil test will determine if a complete fertilizer application is needed.
Frequently, you will need to apply nitrogen (N) to your pasture, but you may not need potash or phosphate. This is especially true in pastures that are actively grazed where little potassium and phosphorous are removed by animals. In these cases, apply nitrogen fertilizers. Again, testing your soil is the only way you can be sure what level and type of fertilization is necessary.
Fertilizing Grass Pastures
Tall Fescue , Orchardgrass and Other Cool Season Grasses
Tall fescue and orchardgrass grown in pure stands can use up to 120 pounds of nitrogen (N) per acre. When producing hay, apply 60 to 80 pounds of N in late winter (February to early March). With favorable summer rains, a second cutting of tall fescue can sometimes be obtained in the summer months. If a summer cutting is attempted, apply 70 pounds of N after the spring cutting of fescue hay. Tall fescue can also be fertilized with 40 to 60 pounds of N in early September with the resulting forage stockpiled or deferred for early winter grazing. Orchardgrass will produce less fall forage than tall fescue. Again, apply phosphorous (P) and potassium (K) as indicated by soil test results.
Hybrid Bermudagrasses and Coastal Bermudagrass and other Warm Season Grasses
(Commonly Grown in the Southern U.S)
These crops will produce high forage yields under good fertility and moisture conditions. For hay fields, apply 75 to 100 pounds of N per acre in spring before growth starts and after each cutting except for the last fall cutting. Rates of P and K needed will vary with current soil fertility and rate of nitrogen application. Follow soil test recommendations for these nutrients. Phosphate can generally be applied in one spring application; however, K may need to be applied in split applications on sandy soils because of leaching. When bermudagrass is grazed, use lower N rates (150 to 200 pounds per acre) during the grazing season. This is the total amount of nitrogen to be applied during the grazing season and should be split into at least two applications to improve nutrient utilization efficiency and provide more even forage distribution.
Bahiagrass and Common Bermudagrass
(Commonly Grown in the Southern US)
These species produce lower yields than hybrid bermudagrass and are usually grazed rather than cut for hay. Apply 100-150 pounds of N in split applications during the grazing season. Base the N rate on the quantity of forage needed. Apply P and K as indicated by soil test results.
Winter Annual Cereal Grains and Grasses (Rye, Ryegrass, Wheat, Oats)
These grasses can use up to 150 pounds of N per acre. Apply 40 to 60 pounds of N at fall planting or when seedlings have emerged and are actively growing. If fall and early winter weather was favorable for growth, a second N application of 60 to 80 pounds per acre in early winter will often stimulate late winter and spring growth. Ryegrass grows longer into the spring and may also benefit from a third N application of 40 to 60 pounds of N in late March or early April.
Fertilizing Legume Monocultures and Mixtures
Legumes can fix nitrogen (N) from the atmosphere and in pure stands do not need additional N. Legumes, however, require higher rates of P and K than grasses and must be supplied these nutrients for good persistence and production. Although legumes fix their own N, grasses growing in association with the clover may benefit from low N rates. If N is used in grass-legume mixes, rates should be timed to minimize grass-legume competition and applied at rates that consider legume proportion of the sward (see below).
Tall Fescue-Clover and Orchardgrass-Clover Mixtures
When tall fescue stands contain a good proportion of white, ladino or red clover, little or no nitrogen is needed. A general rule of thumb is not to apply nitrogen if the clover constitutes greater than 15 percent of the stand. If 5 to 15 percent clover is present, apply 30 to 40 pounds of N per acre; if less than 5 percent clover is present, fertilize the pasture as a pure fescue or orchardgrass grass stand or plant additional clover. It may also be desirable to fertilize with moderate rates of N in early fall or late winter. This will stimulate early grass growth and, if grazed properly, will not negatively impact clover stands. Be sure to supply adequate P and K for best clover productivity and survival.
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