The choice is economic, not agronomic
This question came by e-mail:
Are you a fan of controlled release or straight release fertilizers for spoon feeding N and K, little and often?
What about Potassium?
I know that on very sand rootzones you need to apply little and often of N and K and cheaper forms can be used at much less cost. But, I can also see the potential of controlled release Pottasium [sic] in very sandy systems with high Ksat, low CEC or in areas with lot of rainfall.
But, with controlled release, you are beholden to some phased release where availability is dictated by temperature, warmth or the thickness of the coating. I think that with straight release, you in control and can apply when the turf need it i.e. heave wear, recovery, weather etc.
If I were spoon feeding N and K, little and often, then I would use fast-release (soluble) forms of those elements. I would be controlling the release through the low rates and frequent applications.
Controlled release products have a benefit when one is not spoon feeding. That is, they save labor cost.
One can choose what will work best for a particular site based on an evaluation of fertilizer cost, labor cost, equipment availability, and personal choice. The grass is going to respond the same whether the nutrient supply is controlled by spoon feeding of soluble materials or controlled release of insoluble ones. The choice between controlled release and fast release is economic, not agronomic.