ARS | Publication request: Reductions in potash for last-year alfalfa production

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 23, 2010
Publication Date: November 16, 2010
Citation: Yost, M., Russelle, M.P., Coulter, J., Sheaffer, C., Kaiser, D. 2010. Reductions in potash for last-year alfalfa production [abstract]. In: 2010 Minnesota Forage Research Symposium, November 17-18, 2010, St. Cloud, Minnesota. p. 12.

Technical Abstract: Applying the correct amount of potassium (K) fertilizer is critical for alfalfa yield and stand persistence; however, excess K fertilizer will decrease profits and increase the risk of milk fever when alfalfa is fed to fresh cows. Stand persistence is often not a major concern in the last year of alfalfa production; therefore, K fertilizer applications may need to be reduced. Last-year K fertilizer response of alfalfa in its third or fourth full year of production was tested on 10 farms in Minnesota with medium soil-test K levels (80-120 ppm) in 2008 and 2009. As potash rate increased to 200 lbs KCl/ac, yield increased slightly with early spring application but did not respond if K was delayed until after first harvest. NDFD and ADF increased with either application time, but RFV and RFQ were not improved with additional K. We found no apparent or economic benefit to applying potash in the last year of alfalfa production when soil exchangeable K was greater than 80 ppm at the beginning of that growing season.