Not useless, just a bit more expensive than othe options when you look at how many you are supposed to use per plant. But they should work, I have no idea about supplementing with the liquid K though...

They're useless in the sense that you're supporting the petrochem fertilizer business, helping to degrade our environment by not using environmentally friendly/sustainable organic means of fertilization.

But they're also useless because they are fertilizer salts, which do absolutely nothing to benefit your soil's biological health, which is a key component in healthy plants.

The petrochem argument aside....

My only objection to them is that they dissolve so quickly. Much faster than one would expect or then the manufacturer indicates. I've made the mistake of counting on them being there, still doing their job out of sight, only to have problems quickly develop with the plants. So keep a close eye on them.

And yes, you will have to add some extra K.

Dave

Dave, once I have fruit set and start adding the liquid K would putting a 1/2 gallon of the diluted solution per hill once a week be a good amount to use? They suggest using 1 to 1 1/2 oz per gallon of water. Also, would watermelon benefit from the liquid K? I am fertilizing them with Vegetables Alive 4-3-1 if I am remembering the ratio correctly?