Yes @Jakjazz BHP's Jansen project will be producing...

Yes @Jakjazz BHP's Jansen project will be producing potassium chloride or muriate of potash or MOP (which is the most commonly used form of potassium fertilizer) whereas your Agrimin is a potassium sulphate project. Now this is where their use as fertilizers diverge. K2SO4 or sulphate of potash or SOP is used in certain more valuable crop types and is priced higher than MOP.
Potassium chloride forms a significantly more abundant natural resource than the sulphate form.
Here's a link that fully explains the foregoing
https://investingnews.com/daily/resource-investing/agriculture-investing/potash-investing/types-of-potash-sop-mop/
Cheers