Quote Originally Posted by IAmKowalski
You are correct, PPM is parts per million. This has nothing to do with any one-week interval, it is the level of concentration for a given stage of life, and a plant in full bloom sucks down nutrients a lot faster than one in early veg.
Yes, and no. Let me try and explain in a different way, and ultimately I encourage you to call your nute manufacturer's tech support line to confirm. This is not MY theory, this is simply THEIR instructions.

Ok, let's say that a plant in week 4 of flowering needs 1500 PPM of nutes and drinks on average 2 gallons in a day. Fill 2 gallons of water and add your nutes to achieve 1500 PPM per manufacturer recipe.

Now tomorrow read the PPM and it's at 0 PPM. Your plant drank 1500 ppm. If it was at 1000, your plant drank 500 PPM. If you lowered your nute concentration to 500 it would have been enough for the plant because that's all it uptook, the rest you are wasting.

Finally, whatever the manufacturer's recipe calls for is for ONE feeding per week. This is a concept that is a little harder to understand in hydro because you fill a rez and the plant constantly feeds. So let's say that you filled your rez every day with only as much water as the plant drinks in that one day and added the 1500 ppm as per recipe.

The total amount of nutes (as measured by ppm) that the plant would drink over the course of the week would be plus or minus the 1500 of ONE feeding, not 1500 of 7 feedings.

I know it takes a while to grasp. Contact your nute manufacturer and get some help with it, I'm not asking anyone to believe me.