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Research Project: Enhanced Alfalfa Germplasm and Genomic Resources for Yield, Quality, and Environmental Protection

Location: Plant Science Research

Title: How do new alfalfa varieties respond to K fertilization?

item SHEAFFER, CRAIG - University Of Minnesota
item JUNGER, JAKE - University Of Minnesota
item KAISER, DAN - University Of Minnesota
item Samac, Deborah - Debby
item SCOTT, WELLS - University Of Minnesota

Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: 11/1/2019
Publication Date: 12/1/2019
Citation: Sheaffer, C., Junger, J., Kaiser, D., Samac, D.A., Scott, W.M. 2019. How do new alfalfa varieties respond to K fertilization?. Forage Focus. (December 2019):16-17.

Interpretive Summary:

Technical Abstract: Potassium (K), an essential plant nutrient, has been recognized as an especially important nutrient for alfalfa yield and persistence because of its role in enzyme activity in many plant processes including photosynthesis and biological nitrogen fixation. Previous studies have shown that K fertilization was associated with higher yields, increased winter hardiness and improved disease resistance. However, much of the work substantiating the value of K fertilization was conducted with older alfalfa varieties with less disease resistance and winter hardiness than modern varieties and was conducted on soils with low soil test potassium (STK) levels where a response to fertilization was expected to be dramatic. Six widely grown commercial varieties with fall dormancy 4 and 5 and two new USDA experimental entries with fall dormancy 3 and selected for levels of fibrous roots, were grown at three locations and annually fertilized with 5 rates of K fertilizer (as potassium sulfate) ranging from 0 to 360 lb/acre. Alfalfa varieties had a similar response to application of K fertilizer, and K fertilization was not preferentially beneficial to yield and persistence of any specific variety. The effect of K fertilization on alfalfa forage yield and stand persistence varied by locations that differed in initial STK level and stand age. Higher levels of K fertilization slightly reduced forage crude protein and NDF digestibility. Potassium fertilization has often been related to improved stand persistence. However, very high levels of K fertilization did not meaningfully prolong alfalfa stand life as stands age beyond the third production year. In addition, we observed no effect of K fertilization on root diameter or crown rot score. There was no economic or biological advantage for applying fertilizer at rates above those recommended by the University of Minnesota guidelines to achieve high alfalfa yields.