Ok I was under the impression SOP was better for growing fruits...

Ok I was under the impression SOP was better for growing fruits and vegetables and MOP was for growing grains.

I also though SOP demand was growing rapidly while MOP demand was stagnant I though they were separate markets, but your saying they are interchangeable?

Can a farmer who is growing say carrots and potatoes easily switch from SOP to MOP without any problems?

If so I can't see why does the market for SOP exist at all if it costs more?