Hey Jay, you're only taking an aspirin for the pain with that moss
away product. You'll need to address drainage, airflow, and lack
of sunshine, topsoil, and irrigation, if you really want to grow
turf-grass there.

I have a feeling that I might not have explained clearly in my
original post.

I don't have moss problem in my lawn and I am not against having moss
either. I am trying to use the moss control product not to control
moss, but to use its large quantity of potash (16%) to add potash into
the soil (if this is OK to do so). The good thing is that the moss
control product has large quantity of potash, but without any
phosphate (I have too much phosphate in my soil). It seems to be
perfect for me. However, I don't know if there is any downside of
using it in my lawn.

Jay Chan