This removal is in the range of 40 to 60 lb of K2O per ton of hay harvested. This means that a 5 ton per acre alfalfa crop might remove 300 lb of K2O per acre per year. This reinforces the importance of following soil test recommendations to maintain soil K levels in the optimum range so that there is adequate K to meet this high demand. Be cautious against luxury consumption if K is oversupplied. The bottom line is that you need to supply adequate K for optimum yield but don't apply excess K which could cause problems with your animals.
Legumes are fairly sensitive to boron deficiency.
Drought conditions are particularly conducive to boron deficiency because of reduced organic matter breakdown. This newsletter is available for on-line viewing as an Acrobat PDF file. The Acrobat reader is available at no cost from the Adobe web site. Be sure to pick up the installation instructions. The instructions tell you how to install the Acrobat Reader and how to set it up as a helper application in a variety of web browsers.