Nutrient Feeding Schedule
If you’re using cannabis-friendly nutrients, using the correct pH, and watching ppm of both the water going in and coming out, you shouldn’t have too many problems with deficiencies.
Personally, I find that I run into deficiencies when I’m too careful and don’t give enough nutrients. That’s why I really recommend testing your drainage ppm and keeping a grow journal. Please keep a grow journal for your first several grows as I found it helped me a lot.
Let’s look at a feeding schedule that resembles something from my early days. Let’s use tap water (oh no!), but we’ll let it sit out for two days to evaporate off the chlorine. It usually tests around 170 - 220 ppm, which is a comfortable ppm amount for even seedlings (I don’t recommend more than 300 ppm for seedlings). For seedings, we’ll simply keep the top of the soil slightly wet and give no nutes.
Starting with veg until harvest, we’ll water every other day, alternating clean water and nutrients.
At some point in veg we’re feeding a nute solution that is 700 ppm with around 600 ppm of that coming from nutes we put into the water. If we feed that on Monday, we will then give clean water on Wednesday and test the drainage. Say that comes out to 400 ppm, so now we know our plant is eating around 150 ppm a day. So on Thursday, we can assume there is only going to be 250 ppm left in the medium, then on Friday that will be 100 ppm, so we feed again.
If we start seeing deficiencies, then we can assume that the medium having only 500 ppm is too low (it probably is) and we want that number to go higher until the deficiencies stop. We can either feed earlier on Thursday when the ppm is down to 250 ppm or just feed heavier on Monday. Do want makes you comfortable.
It’s probably better to just feed heavier if you want to keep it on a set schedule, but if you’re worried about nute burn then feeding less more frequently is fine. When I first started using coco coir, I feed nutes every time I watered. Most growers alternate with clean water so salt doesn’t build up, but a good flush when moving from veg to flower fixes that. Find what works for you. Soil users will want to watch watering as often as coco coir users.
Growing cannabis is an art and science and here is where you can really see why.