My time to shine
I use GH nutes exclusively with autos. I have several failures under my belt, and a couple of successes, so here's what I've learned -- take it with a grain of salt
(I'm also a relatively new grower).
Like
@Mañ'O'Green says above, they have "old" and "new" schedules. The "old" schedules are backed by a hell of a lot of successful and trustworthy grows, so there may be an element of "don't fix what's not broken" here. Having said that, here's a brief breakdown of the old charts vs. the new charts:
Old Feed charts: (you'll find these on Google Image searches and old blog posts)
- Separate charts for "recirculating" and "drain-to-waste" applications; drain-to-waste being better suited for non-hydroponics, e.g., soil and soilless applications
- A staggered/add-on approach, e.g., a popular feedchart is the Trio + extras like Cal-Mag.
- Adding extras means maintaining the base/trio in their original concentrations
- e.g., Week 2 "Simple" program has Micro-Gro-Bloom in 4-5-1 concentrations; adding Cal-Mag in the "Expert" program just means adding Cal-Mag with no changes to the base 4-5-1 Simple Program, even though Cal-Mag contains nitrogen
New Feedcharts: (you'll find these on the GH website, only as of the past year or so)
- No more "recirculating" or "drain-to-waste"
- No more "Simple" or "Expert"
- Now feedcharts are divided into "light", "medium", and "aggressive"
- These apply to how many irrigation events per days, i.e., aggressive for 1 or less irrigations per day, light for five+ irrigations per day
- Primary difference is based on ppm:
- Aggressive Feedchart has max of 1300ppm in late veg
- Medium Feedchart has max of 1050ppm in late veg
- Light feedchart has max of 950 in late veg
- Feedcharts are now in 3, 6 and 10-part formulas
- Now the base nutrients in the 6 and 10 part formulas are adjusted to account for the N-P-K ratios provided from the "add-ons"
- e.g., Cal-Mag contains nitrogen, so the Micro-Gro-Bloom concentrations are adjusted in the 6-part to account for the extra nitrogen coming from the cal-mag
Applying these to Autoflowers:
@Mañ'O'Green has an awesome stickied post where we talks about his nutrient solution ppms, and aims for ~500-550 throughout most of the grow. This means using the above feedcharts as a guide and scaling them down appropriately. The photoperiod feedcharts have higher nutrient concentrations in veg, and lighter concentrations in flowering. Auto on the other hand seem to prefer relatively consistent feedings of around 500ppm outside of the seedling stage. For me, I end up feeding ~50% during veg, and then up to 100% in late flower. My most recent feeding for example was 75% of the medium mid-bloom chart, which worked out around 535ppm excluding my 35ppm starting water.
*Note: the provided ppm range for full strength medium mid-bloom is 800-1000ppm. When I scaled this to 75%, I measured 535ppm + 35ppm starting water. Since 75% of 800-1000ppm is 600-750ppm, it seems the GH reported ppms assume a starting water of 65-215ppm. Just something to keep in mind*
In Coco
You want Cal-Mag (assuming soft water - see below), so that means following either the 6- or 10-part solutions in their entirety:
https://generalhydroponics.com/resources/floraseries-feedcharts/
Scale the above to ~500-550ppm or so, excluding starting water! (again, see below)
Starting water ppm
On
@Mañ'O'Green's link above, he talks about different requirements of micronutrients like calcium, of which cannabis needs 80-180ppm. If your water has 180ppm of calcium already in it, then you don't need the calcium, but hard water + coco is probably its own can of worms. If your water is "too hard" you might want to look into softening it. Hopefully someone else can chime in on this as I've never grown in coco, and I'm blessed with foolishly soft water where I live.
Disclaimer
You can check out my current grow from the link in my signature. I'm following the 10-part GH series, but I still don't have my nutes fully dialed in and ran into some issues. I'm attributing it to two things:
- I'm growing in a peat-based medium amended with dolomite lime, so I'm probably feeding unnecessary calcium; you shouldn't run into this issue in coco (unless you're water is hard
)
- I overfed very early on in veg, then underfed afterward and overcorrected. I wish I had of found @Mañ'O'Green's nutrient post earlier where he talks about his 500ppm target.
Misc.
It goes without saying you'll still need to pH everything that goes into your pot, especially in coco. Again, follow
@Mañ'O'Green's link above. I think 5.8-6.2 is the target for coco?
Anyways, happy growing!
-tronN00dles
