Tell that to the snow!
Apparently, the little white lumps in the bottom of the grape juice bottles are either Potassium tartrate or calcium tartrate. I'm going to try using them as part of the organic fertilizer for my hydroponics garden.
The main nutrients in any fertilizer are N - P - K, or Nitrogen, Phosphorus, Potassium. When you see the three numbers, that's what they're talking about.
I've been trying for years to create a natural "balanced" fertilizer. So I could use compost water for the nitrogen, ash for the phosphorus, and maybe these things for the potassium and/or calcium.
Try it, anyway.
Right now my climbing tomatoes are about 8 inches tall and happy, aside from the lack of sunshine (again, blame the snow).
The phrases below are some that I used to find this information.
diprotic organic acid