No, not really. You would be about right for potassium [K], but the plants would have no nitrates [NO3] which they need to grow. The beauty of KNO3 is you have two key ingredients in one chemical compound.
Try an internet search. You may find that KNO3 and other nitrates have become 'regulated substances'. They can still be purchased but the seller has to keep records of the purchaser. Internet sales will yield your name and address and a statement about age (over 18yrs usually works) and why you want the chemical - as a plant fertilize will provide the vendor with these details. All legitimate. Garden Centers take the easy way out and tend not to stock it. They try and sell a blended fertilizer for terrestrial plants which might contain ammonium salts or urea. Hope this is of help.