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Agronomic Crops Network

Ohio State University Extension

CFAES

Pre-Establishment

Pre-Establishment Fertilization and Limiing

Soil pH

Proper soil pH and fertility are essential for optimum economic forage production. Take a soil test to determine soil pH and nutrient status at least six months before seeding. This allows time to correct deficiencies in the topsoil zone. The topsoil in fields with acidic subsoils (most common in eastern Ohio) should be maintained at higher pH than fields with neutral or alkaline subsoils.

Topsoil pH Levels for Forages:

  • 6.8 for alfalfa on mineral soils with subsoil pH less than 6.0.
  • 6.5 for other forage legumes and grasses on mineral soils with subsoil pH less than 6.0.
  • 6.5 for alfalfa on mineral soils with subsoil pH greater than 6.0.
  • 6.0 for other forage legumes and grasses on mineral soils with subsoil pH greater than 6.0.

Soil pH should be corrected by application of lime when topsoil pH falls 0.2 to 0.3 units below the recommended levels. With conventional tillage plantings, soil samples should be taken to an 8-inch depth and lime should be incorporated and mixed well in the soil at least six months before seeding. If more than 4 tons per acre are required, half the amount should be incorporated deeply and the other half incorporated lightly into the top 2 inches. If low rates of lime are recommended or if a split application is not possible, the lime should be worked into the surface rather than plowed down. This assures a proper pH level in the surface soil, where seedling roots develop and where nodulation begins in legumes.

Phosphorus and Potassium

Corrective applications of phosphorus and potassium should be applied prior to seeding regardless of the seeding method used; however, fertilizer applications incorporated ahead of seeding are more efficient than similar rates not incorporated. This is especially true for phosphorus and for no-till seedings. Phosphorus and potassium fertilizer recommendations for forages are provided in Tables 7.5 to 7.7. More details are available in OSU Extension bulletin 974 Tri-State Fertilizer Recommendations for Corn, Soybean, Wheat, and Alfalfa, which is available online at extensionpubs.osu.edu/tristate-fertilizer-recommendations-for-corn-soybeanwheat-and-alfalfa.

Picture of collage of Table 7.5. Annual phosphate (P2O5) recommendations for pure grass forage stands; includes maintenance plus 4-year buildup to the critical level where needed; Table 7.6. Annual phosphate (P2O5) recommendations for forage legume or legume-grass mixtures; includes maintenance plus 4-year buildup to the critical level where needed; Table 7.7. Annual potassium (K2O) recommendations for forage grass only, legume only and legume-grass mixtures; includes maintenance and 4-year buildup to the critical level where needed

Sulfur

Sulfur is an essential secondary plant nutrient and is a component of plant proteins and vitamins. In the past, the supply of sulfur in Ohio soils was more than adequate for good forage growth; however, with the implementation of the Clean Air Act, there has been a 30%–40% reduction in sulfur deposition to Ohio soils since 1985. Sulfur deficiencies on alfalfa have been documented in a few Ohio soils. If soils have exhibited sulfur deficiency in the past, consider applying 70 pounds per acre of elemental sulfur ahead of seeding alfalfa. Elemental sulfur requires at least two months to be converted in the soil to the sulfate form that is available for plant uptake. If more rapid uptake of sulfur is desired in the seeding year, add 30 pounds per acre of a sulfate form of sulfur at seeding along with the elemental sulfur that will be in the available sulfate form in subsequent years. A sulfur deficiency is unlikely on soils where manure or gypsum have been applied, since both are good sources of sulfur. Refer to bulletin 974 Tri-State Fertilizer Recommendations for Corn, Soybean, Wheat, and Alfalfa for additional information on fertilizing forages.

Pre-Establishment Fertilization for NO-TILL

For no-till seedings, take soil samples to a 4-inch depth to determine pH and lime needs, and to a normal 8-inch depth to determine phosphorus and potassium needs. If possible, make corrective applications of lime, phosphorus, and potassium earlier in the crop rotation when tillage can be used to incorporate and thoroughly mix these nutrients throughout the soil. When this is not feasible, be sure to make lime, phosphorus, and potassium applications at least eight months or more ahead of seeding to obtain the desired soil-test levels in the upper rooting zone. Use the finest grade of lime available at a reasonable price when surface applications are made. Lime and phosphorus move slowly through the soil profile. Once soil pH, phosphorus, and potassium are at optimum levels, surface applications of lime and fertilizers can maintain those levels. Attempts to establish productive forages often fail where pH, phosphorus, or potassium soil-test values are below recommended levels, even when corrective applications of those nutrients are surface applied or partially incorporated just before seeding.

Starter Nitrogen

Seedling vigor of cool-season forage grasses is enhanced on many Ohio soils by nitrogen applied at seeding time. Apply nitrogen at 10 to 20 pounds per acre when seeding grass-legume mixtures and 30 pounds per acre when seeding pure grass stands. Starter nitrogen applications of 10 pounds per acre may be beneficial with pure legume seedings, especially under cool conditions and on soils low in nitrogen. Manure applications incorporated ahead of seeding can also be beneficial to seedling establishment of forages, including alfalfa. Obtain a manure nutrient analysis and base application rates on soil-test results. For more information on manure application to soils, visit ocamm.osu.edu/.