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Sulfur and Potassium Management of Alfalfa

How much extra sulfur and/or potassium do we need for optimum production?

Soil can supply large amounts of potassium (K) but producers and agricultural advisors are reluctant to eliminate K use for large K consumers like alfalfa fearing reduced yield and/or winter kill. In addition, sulfur (S) deposition rates have drastically decreased over the past 10 years and recent on-farm trials show a yield response to S addition, possibly due to the role S plays in N fixation by alfalfa. Both K and S are macronutrients essential for crop growth. Producers wanted to know: (1) whether S and K applied with manure in corn years is sufficient to bridge alfalfa years in rotations; and (2) what tools to use to reliably identify if extra S or K are needed. For K management, three approaches are commonly used: (1) K removal, (2) soil test K, and (3) K saturation-based methods. Recommendations for K for alfalfa can vary from 0 to 145 lbs K2O. Potassium application comparisons were done to determine impact of K addition on crop yield, stand survivability, and forage quality for soils ranging in soil test K.

For S management, recent NY farm trials conducted as part of this project resulted in the calibration of a new soil test for S; tissue testing was effective in identifying S deficient sites as well. Recommendations for S are 20-30 lbs S/acre for S deficient sites.

Once the new Cornell sulfur test was calibrated for alfalfa and K recommendations based on the Cornell Morgan test were confirmed accurate, we evaluated 50 alfalfa fields (across the state; two fields per farm) for potassium and sulfur status through both tissue testing and soil testing at 3rd cutting for two years (2012 and 2013 growing seasons). Farmers were invited to submit yield, tissue and soil data for two fields, ideally one field for which a S or K deficiency might be expected, and one for which a deficiency in either macronutrient is unlikely.

If you are interested in participating, contact Quirine Ketterings ( or 607-255-3061). You can also write to: Quirine Ketterings, Nutrient Management Spear Program, Department of Animal Science, Cornell University, 323 Morrison Hall, Ithaca NY 14853.


  • Evaluate soil and tissue testing approaches for sulfur management of alfalfa.
  • Evaluate methods for determination of K saturation.
  • Re-evaluate K recommendations for alfalfa based on soil test K levels and K saturations.
  • Evaluate soil test K (Morgan test) versus K saturation approaches.

Funding Sources

Additional Resources

Farmer Impact Stories

Fact Sheets

Extension Articles

    • Sadeghpour, A., Q.M. Ketterings, G. Godwin and K.J. Czymmek (2017). Impact of manure injection on alfalfa and grass hay stands. What’s Cropping Up? 27(1): ?-??
    • Sadeghpour, A., K.J. Czymmek, Q.M. Ketterings (2016). Value of manure lingers long after application. Eastern DairyBusiness. The Manager. 8(2): 37-38.
    • Czymmek, K.J., and Q.M. Ketterings (2015). Taking care of (manure) business – Strive to do the best possible job every time manure is applied. Eastern DairyBusiness. The Manager. 7(1): 16.
    • Ketterings, Q.M., G. Godwin, S. Gami, K. Dietzel, J. Cherney, and K.J. Czymmek (2012). Sulfur for alfalfa in New York State. What’s Cropping Up? 22(2): 12-16.
    • Czymmek, K.J., and Q.M. Ketterings (2012). Managing soils for better crops. Eastern DairyBusiness; The Manager 4(2): 28.
    • Ketterings, Q.M., G. Godwin, J. Cherney, and K. Czymmek (2011). Effect of Manure, Compost, and Potassium Application on Alfalfa Yield, Potassium Content and Soil Test Potassium in Aurora, NY. What’s Cropping Up? 21(4): 8-12.
    • Ketterings, Q.M., G. Godwin, J. Cherney, and K. Czymmek (2011). Comparison of Tissue K and Whole Plant K for Alfalfa. What’s Cropping Up? 21(4): 13-15.
    • Ristow, P.L., S. Moss, Q.M. Ketterings, K.J. Czymmek (2011). Understanding manure nutrient variability. What’s Cropping Up? 21(4): 19-23.
    • Maguire, R., D. Beegle, J. McGrath, and Q.M. Ketterings (2011). Manure injection in no-till and pasture systems. Extension Publication. Mid Atlantic Water Program.
    • Czymmek, K.J., Q.M. Ketterings, and J. Cherney (2011). Soil may supply adequate K. Eastern DairyBusiness 3(2): 22-23.
    • Ketterings, Q.M., K.J. Czymmek, and J. Cherney (2011). Rethink added sulfur for alfalfa. Eastern DairyBusiness 3(2): 28-29.
    • Czymmek, K.J., and Q.M. Ketterings (2010). Managing potash in a dairy rotation. Eastern DairyBusiness 2(2): 12-13.
    • Ketterings, Q.M., J.H. Cherney, and K.J. Czymmek (2009). 10 tips to manage manure on alfalfa-grass fields. Eastern DairyBusiness 1(2): 20 (+23).
    • Czymmek, K.J., Q.M. Ketterings, and J.H. Cherney (2009). Potassium management makes good sense. Eastern DairyBusiness 1(2): 22-23.
    • Ketterings, Q.M., J.H. Cherney, K.J. Czymmek, E. Frenay, S.D. Klausner, L.E. Chase, and Y.H. Schukken (2008). Manure use for alfalfa-grass production. Department of Animal Science Mimeo 231/Department of Crop and Soil Sciences Extension Series E08-3. Cornell University. 43 pages.
    • Ketterings, Q.M., and K.J. Czymmek (2007). Are manure and established alfalfa a good mix? The Manager. Northeast DairyBusiness 9(2): 14-15.
    • Ketterings, Q.M., S.D. Klausner, and K.J. Czymmek (2003). Potassium guidelines for field crops in New York. CSS Extension Series E03-14. Cornell University, Department of Crop and Soil Sciences, Ithaca NY. 41 pp.

    Journal Articles

    • Ketterings, Q.M., S. Gami, R.R. Mathur, and M. Woods (2014). A simple method for estimating effective cation exchange capacity, cation saturation ratios and sulfur across a wide range of soils. Soil Science 179:230-236.
    • Ketterings, Q.M., G. Godwin, S. Gami, K. Dietzel, J. Lawrence, P. Barney, T. Kilcer, M. Stanyard, C. Albers, J.H. Cherney, D. Cherney, K.J. Czymmek (2012). Soil and tissue testing for sulfur management of alfalfa in New York State. Soil Science Society of America Journal 76(1): 298-306. (doi:10.2136/sssaj2010.0437).
    • Ketterings, Q.M., C. Miyamoto, R.R. Mathur, K. Dietzel, and S. Gami (2011). A comparison of soil sulfur extraction methods. Soil Science Society of America Journal 75(4): 1578-1583.