PPM best practices for Feeding Autoflowers in Soil?

Over the past month or more I've been digging and re-digging for some solid & more definitive advice on feeding autos in soil.

Lots of all-over-the-place info that goes from "feed 1/4th strength' of whatever chart you choose, to feed half; all the way to "feed full strength".

Anyone provide a solid schedule by PPM of where I should be doing this? Right now, early-to-mid Flower in soil I've been aiming at 550-650PPM (total, including my well-water which starts at ~220). I'm using the standard General Hydroponics Flora Trio. I've fussed with a few schedules (none specifically for Auto, but knocked down by about half).

What's the real story, folks. What do 'experts' say, what are your reports from the battlefield?

There is no one right answer. There is just to many variables. Do your plants seem good with the 550-600 ppm ? If so there ya go. Mine liked to be around there in flower. Consider how hard you are driving your plants and the environment they are growing in. It's going to determine how much you feed. Are you growing with 1000w HPS and CO2 ? If so You might want to feed higher. Are you growing an Autoflower or Photo period. Soil or hydro ? Have you hit the target VPD ? See how all the variables change things ?

Look at your plants at 600 ppm. Are they too dark of green or too light ? Do you have burnt tips or clawing ? Nobody can tell you how much to feed your plant but you alone.

Zogs said:

There is no one right answer. There is just to many variables. Do your plants seem good with the 550-600 ppm ? If so there ya go. Mine liked to be around there in flower. Consider how hard you are driving your plants and the environment they are growing in. It's going to determine how much you feed. Are you growing with 1000w HPS and CO2 ? If so You might want to feed higher. Are you growing an Autoflower or Photo period. Soil or hydro ? Have you hit the target VPD ? See how all the variables change things ?

Look at your plants at 600 ppm. Are they too dark of green or too light ? Do you have burnt tips or clawing ? Nobody can tell you how much to feed your plant but you alone.

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I'm really not looking for specifics but for actual starting places to adjust from...that's the 'best practices' thing...I know there's no one answer to it, but everyone's 'start here' is completely different. Also (as the title suggests) autos in soil. There's really not much of a solid start point to tweak from. Given the popularity of Autos these days and the number of people using soil, you'd think there'd be some base info involved.

One thing to look out for when feeding inorganic nutrients in soil is PPMs building up. When feeding organics in soil, we don't feed to runoff, but it can be a good idea with inorganic nutrients, similar to coco. On the days you are feeding, I'd allow for plenty of runoff, just to flush any salts leftover from previous feeds. 500-600 ppm is good for full sized plants, end of veg to flower. It isn't a one size fits all solution but it's a great place to start. If you notice real deficiencies, you might need to feed a bit more-but lots of times what people think are deficiencies are actually problems of excess or PH being out of range. For your first grow, just try to keep your leaves looking as perfect as possible, a nice deep green without burned tips. If you burn your tips, no problem, just back off the nutrients a little. If you use a balanced nutrient (which you are) and keep the leaves healthy, nice buds will follow. Also, be sure you are watering when the pots get light, and not on any fixed schedule-overwatering is easy to do before you get a handle on things. Good luck!

Rurumo said:

One thing to look out for when feeding inorganic nutrients in soil is PPMs building up. When feeding organics in soil, we don't feed to runoff, but it can be a good idea with inorganic nutrients, similar to coco. On the days you are feeding, I'd allow for plenty of runoff, just to flush any salts leftover from previous feeds. 500-600 ppm is good for full sized plants, end of veg to flower. It isn't a one size fits all solution but it's a great place to start. If you notice real deficiencies, you might need to feed a bit more-but lots of times what people think are deficiencies are actually problems of excess or PH being out of range. For your first grow, just try to keep your leaves looking as perfect as possible, a nice deep green without burned tips. If you burn your tips, no problem, just back off the nutrients a little. If you use a balanced nutrient (which you are) and keep the leaves healthy, nice buds will follow. Also, be sure you are watering when the pots get light, and not on any fixed schedule-overwatering is easy to do before you get a handle on things. Good luck!

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Thank you. Seems like I'm mostly in the right place. The majority of my plants have been a happy medium-ish green...I did have one plant that started yellowing towards the bottom and looked 'hungry' though I'd been feeding. I hadn't been watering to runoff (or at least not much runoff) to that point, so I took that one, brought it outside and put 5g of water through it. The PPM on the runoff went from ~2500 down to ~330. My soil pH remained solid through this. It was around 6.5 and ended up at 6.5. I followed that move with a re-feed but slightly lighter than the others and it seemed to solve the yellowing fairly quickly (less than a week).

Here's a question, when I do feed, my water starts at 220ppm (.440EC), I've been aiming to get my total TDS @ 550-650ppm. Is this correct, or should I be looking at 770-870ppm which would be 229 for the water and 550-650 worth of nutrients?

Half this grow has been learning about watering. The soil I have is decent but I didn't amend with enough perlite (actually I also used vermiculite, which I didn't realize would hold water rather than drain it too). Once I realized the hows and whys to drain to a good amount of runoff, things seem to be getting better.

LeastExpectedGrower said:

I'm really not looking for specifics but for actual starting places to adjust from...that's the 'best practices' thing...I know there's no one answer to it, but everyone's 'start here' is completely different.

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If anyone gives you an answer it's just guesswork. You trying to make an apples to apples comparison when you have golden delicious and they have granny smith. You would need to be quite a bit more specific. We don't even know what kind of soil you have, what amendments are already in it. How often are you feeding. Every day ? 2x a week ? It's all different. On top of that nobody knows what strain you have and if they are nute sensitive or big feeders. The point I'm trying to make is there is no one starting point that fits all. Start with a low dose of nutes and work your way up according to your plants. Or maybe you shouldn't even start with nutes if you soil already has enough.

As for the water, nobody knows what minerals are in your water.

Zogs said:

If anyone gives you an answer it's just guesswork. You trying to make an apples to apples comparison when you have golden delicious and they have granny smith. You would need to be quite a bit more specific. We don't even know what kind of soil you have, what amendments are already in it. How often are you feeding. Every day ? 2x a week ? It's all different. On top of that nobody knows what strain you have and if they are nute sensitive or big feeders. The point I'm trying to make is there is no one starting point that fits all. Start with a low dose of nutes and work your way up according to your plants. Or maybe you shouldn't even start with nutes if you soil already has enough.

As for the water, nobody knows what minerals are in your water.

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I feel like you're missing the intent of my post and my question. As I said before I was looking for the generalities, not the specifics. In the meantime, others have presented some good sound starting points.

LeastExpectedGrower said:

I feel like you're missing the intent of my post and my question. As I said before I was looking for the generalities, not the specifics. In the meantime, others have presented some good sound starting points.

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I know I'm being a bit harsh with my answers. But it's because you already have a good grasp on reading your plants yourself. It seems like you just need a good boot out of the nest. And I stand by my statment nobody is going to be able to give you good advice without getting into very specific details

From all the details about feeding, it sure makes me feel like I'm behind the times. After 20 years of growing in soil such as BB, Promix etc...autos and photos....I've just used a up to 25% strength of nutes. Only check ph and letr rip. Never checked ppm anything.

Oldreefer said:

I've just used a up to 25% strength of nutes.

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even under those big ol 600-1000w hps back in the day ? I think 25% is fine in those soils under led,, but who knows how hot other soils are.

Zogs said:

even under those big ol 600-1000w hps back in the day ? I think 25% is fine in those soils under led,, but who knows how hot other soils are.

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Yep...I was always very conservative. and simple. Oh sure, I've done the 'grow a monster' thing but being perpetual for over 20 years, with plants at all stages at all times, it's just easier to do it the simple method.....I always stick to the milder soilless mixes.

Oldreefer said:

From all the details about feeding, it sure makes me feel like I'm behind the times. After 20 years of growing in soil such as BB, Promix etc...autos and photos....I've just used a up to 25% strength of nutes. Only check ph and letr rip. Never checked ppm anything.

Click to expand...

Getting comfy with the right amount of nutrients has been the challenge. I've been using General Hydroponics' Flora Trio and every site, every Tom, Dick & Harry has their own feed schedule for them. At this point, since I've hit 10 weeks past germination and this is my 5th week of flower, pretty much all value in the soil should be pretty used up. I used Black Gold, which is known to be 'hot' but now with the amount of water, etc. that's been through my bags, it's pretty neutral. Alas, it's also more dense than I'd like, but my feeding/watering schedule has altered sufficiently that I'm not over/under watering at this point.

I wasn't paying too much attention to the TDI stuff really, until I hit a point where one of my plants (the tallest & best performing so far) started yellowing lower down. I asked a few questions and got some kind of crap answers like "that's what happens when your plant is almost done," which made no sense in the 3rd week of flower with pistils white as snow. I did say that I felt that this was not an excess problem but just seemed like a deficiency and luckily someone came along and agreed...which meant I needed to figure out why, even with feed it was happening. I started suspecting lockout and that's when I started testing the PPM. The soil pH with both slurry and runoff was nailed pretty good at 6.5 but the runoff PPM was well up in or past the 2500ppm range. I flushed well with pH'ed water down to 330ppm and fed at 550ppm at the end of the flush. Within a week things were getting green again, minus the leaves that were too far gone.

None of the other plants (including a 'matching' Northern Lights auto) had the same issues, though I did follow up and run a few gallons through them all anyway. Incidentally, the most finicky plant of the bunch is a Blueberry auto that's more sensitive and expresses nutrient burn when the others are fine.

Next grow I'll be moving to Promix, as it I believe is closer to what I want...a bit more neutral in content as well as being a little lighter, though I'll amend with perlite, etc. as well. I do have a handful more auto seeds so I'll do another batch, but will probably move to photoperiod as soon as feasible.

Addendum:

I purchased some General Hydroponics Flora Micro Hardwater.

On first use, I'm actually pretty enthusiastic about it. Using the GH Trio "light" schedule at 50% my PPM's were right around 500-550, while they'd been closer to 650-700 with the standard Micro. pH adjustment was a little different, but not horribly much so. Fed @550ppm and have had no issues with the plants.

LeastExpectedGrower said:

Over the past month or more I've been digging and re-digging for some solid & more definitive advice on feeding autos in soil.

Lots of all-over-the-place info that goes from "feed 1/4th strength' of whatever chart you choose, to feed half; all the way to "feed full strength".

Anyone provide a solid schedule by PPM of where I should be doing this? Right now, early-to-mid Flower in soil I've been aiming at 550-650PPM (total, including my well-water which starts at ~220). I'm using the standard General Hydroponics Flora Trio. I've fussed with a few schedules (none specifically for Auto, but knocked down by about half).

What's the real story, folks. What do 'experts' say, what are your reports from the battlefield?

Click to expand...

I strongly reccomend jacks classic 20-20-20 and jacks classic bloom booster for flowering. I use 50% peat-50% perlite with 1 tsp pulverized dolomite lime per gal of soiless mix. Ph tap water to 6.3-6.5 and you literally cant go wrong. Start feeding 1/8 strength when first 3 leaf leaves appear and slowly increase to full strength jacks every other watering outdoors. Simple, simple and all plants grown in this system do great so far. You almost cant burn or hurt your plants with the jacks, its almost fool proof.

lemmis said:

I strongly reccomend jacks classic 20-20-20 and jacks classic bloom booster for flowering. I use 50% peat-50% perlite with 1 tsp pulverized dolomite lime per gal of soiless mix. Ph tap water to 6.3-6.5 and you literally cant go wrong. Start feeding 1/8 strength when first 3 leaf leaves appear and slowly increase to full strength jacks every other watering outdoors. Simple, simple and all plants grown in this system do great so far. You almost cant burn or hurt your plants with the jacks, its almost fool proof.

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Have you tried a lower ph? Weed scientist says 5.5 ph is ideal, he uses jacks, peat, lime, gypsum and vermiculite. Curious have you tried lower?

im trying to try but just realized my ph pen has been messed for a month or so, just trying to see any green leaves at the moment.

I used to be at 700 ppm with Dyna-Gro grow on everything, photos and autos and it went well, I believe that was after 200 ppm tap though, not positive.

OneMoreRip said:

Have you tried a lower ph? Weed scientist says 5.5 ph is ideal, he uses jacks, peat, lime, gypsum and vermiculite. Curious have you tried lower?

im trying to try but just realized my ph pen has been messed for a month or so, just trying to see any green leaves at the moment.

I used to be at 700 ppm with Dyna-Gro grow on everything, photos and autos and it went well, I believe that was after 200 ppm tap though, not positive.

Click to expand...

My recent shift to GH hardwater does make a difference. My well/tap water runs in the range of ~220 and now I can effectively end up in the 500-600 range without cutting the percentages on schedule too much. Eventually I may dip my toes in doing a soilless grow, but I want to sort of do a bunch of runs the 'old fashioned way to get used to things before I screw with stuff too much.

My pH meter gets calibrated every 2-3 uses and I know what range my water is, so if I dip and the number is funky I do a quick calibrate. One of the things on the upgrade list will be a decent meter one of these moments. Probably sometime in the next grow.

here is one I messed up after heavy flush, still low ph, I think my pen took a crap at the tail end of making nutes and I didn’t catch it. The next time I used it, so far off won’t calibrate anymore.

Really what I wanted to share was the ec pen and that the actual media is much lower and that is what I am looking at now for ideal ec numbers.

Plant looks like shit, I know

Better look at the pen, took this and noticed still improper solution left in my lines, okay to get my ph up a bit though. Maybe I did that on Purpose.