I read it that he has a grand total of 10 to 13 stems/sq ft not plants. That could be one crown with 13 stems on it.

In theory we want 40 or 50 stems/ft² and or 3 to 5 plants per ft².

In the good old days we always followed alfalfa with a crop that had large seeds, as in corn or cotton. With the new planters and no till drills you can plant about anything you want.

If contemplating going back to alfalfa, consider winter wheat. Then plant alfalfa back into the wheat stubble. Spread your lime before planting the wheat and maybe the pH and calcium will be improved enough for alfalfa. Do not short the potash and phosphate.(if you think you need 150 units of K₂O apply 300 or so) If you have enough potash you can apply 6 years worth of phosphate prior to planting, and realize more total production than top dressing every year or two. 

Note for my heavy clay soils, CEC 40 to 60, soil test 400 ppmK (VH) I see a positive crop response with 1,000/A of Murate of potash, a few times more.  This is plowed in and usually persist for the duration of the stand.