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Switchgrass Fertilizer and Lime Recommendations

Crop and Soil Environmental News, May 1997

Steve Donohue
Extension Specialist, Soil Testing
Dale Wolf, Retired
Extension Specialist, Forages

Dale Wolf and I sat down recently and developed fertilizer and lime recommendations for switchgrass based on Dale's research on this grass. In general, switchgrass grows very well at low pH levels and shows minimal response to fertilizer application. Here are preliminary recommendations until more definitive soil fertility research can be completed:

  1. Lime - desired soil pH = 5.8 or higher. Refer to "Soil Test Recommendations for Virginia," March 1994 (page 94) for amount of limestone to apply.

  2. Nitrogen - do not apply N in the establishment year. (Without N switchgrass out-competes weeds for water and nutrients.) However if establishment has been successful and forage is needed later during the establishment year, apply 50 lbs N/A in July.

    For "maintenance" in subsequent years, where two hay cuttings are taken per year, do not add N in the spring; make one 40 lb N/A application right after the first hay cutting (between June 15 - June 25).

  3. Phosphorus - for Low soil test, apply 100 lb P2O5/A. At Medium test level, apply 50 lb P2O5/A. At High and Very High, no P2O5 is needed.

  4. Potassium - for Low soil test, apply 100 lb K2O/A. At Medium test level, apply 50 lb K2O/A. At High and Very High, no K2O is needed.

  5. Calcium, Magnesium - separate applications of these nutrients are not recommended. In situations where magnesium tests Low, and limestone is needed, use dolomitic lime.

  6. Sulfur - little/no response is expected.

  7. Micronutrients - little/no response is expected.

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