I’ve often recommended that folks make a fertilizer concentrate and dispense that when mixing up solution for application to their plants, and even demonstrated a convenient way to do that with a Bettix bottle, so now we stock them.
All you do is open the cap on the larger chamber of the bottle, dump in the appropriate amount of fertilizer powder, and fill with 2 quarts of water. Replace the cap and shake well, and you now have 64 ounces of concentrate, which when dispensed at 1 ounce/gallon, will make a 100 ppm N solution – perfect for weekly feeding.
Dispensing is also simple: remove the cap from the smaller chamber of the bottle (leave the large one sealed) and gently squeeze the bottle. The concentrate moves up the small tube and into the graduated portion, so you can dispense up to 4 ounces per squeeze.
You may use this with any water-soluble fertilizer. A reasonable, quick calculation is to divide 8 by the %N and round the answer, which is cups of powder to add to 2 quarts of water, giving you a 1 ounce-per-gallon concentrate for a 100 ppm N final solution. Here are a few amounts to use for common orchid fertilizers (this table is affixed to the bottle, for your convenience):