Sulpomag or K Mag (0-0-22_K-11_Mg-22_S) has proved to be worthwhile here. Prior to planting alfalfa I apply at least half the K and P I expect the crop to need during a 5 or 6 year stand.

I am looking at 600 lbs K2O/A using 500 lbs Potash and 1500 lbs of K Mag. This system increases the soil test more for ppm K than 1,000 lbs of MoP, and the initial tissue analysis is higher with the MoP & K Mag combination.
My object is to have the first season's plant analysis to be in the 2.75 to 2.85 ppm K range. The how and why is a mystery to me, but I assume the soil welcomes the little extra magnesium as well as the sulfur, or that there is too much chlorine with the MoP only. Maybe a little of all the above?

With our July and August drought the stand is thicker going into the second year if the K levels are a little on the high side.


That Indiana black heavy clay soil interest me. I was wondering if you also have a high pH and excessive calcium levels as we do. Have you had a measured CEC value determined? My lighter soil has a 40 meq/100g CEC while our heavy clay will be above 50 meq/100g CEC value reported. The favorite Computed CEC values for these soils vary widely from the measured, both higher and lower.
With the exception of the 2007 season we do not see all that much rain and try to retain all that we can.