Soil not drying quickly enough (autoflower)

Hello everyone,
my soil (Biobizz lightmix) is not drying quickly enough.

As you can see in attached pictures, I have two small autoflower plants (day 22) growing together in one large plastic pot (17 L / 3.5 gal). They are now entering the preflower stage (it is Syrup strain, quick flowering 55-65 day in total). I realize this two plants / one pot setup isn’t ideal, but I had my reasons and it is what it is for this grow.

The soil takes about 6-8 days to dry properly — meaning roughly the top half of the soil is completely dry. My last watering was 4 L (0.8 gal) with about 10% runoff. This watering interval feels too long for a proper nutrient schedule, as from my research, feeding twice a week is recommended.

To improve aeration, I even drilled multiple holes into the sides of the pot, inspired by airpots.

Here are the options I’m considering:

1. Feed once a week when the soil is dry (using the recommended nutrient ratio) with about 10% runoff. My concern here is that the plants might not get enough nutrients, potentially reducing yield.
2. Feed once a week when the soil is dry, but double the nutrient concentration, 10% runoff.
3. Feed twice a week with the recommended nutrient ratio, but with a smaller volume of water and no runoff. My concern here is the possible buildup of salts in the soil.
4. Transplant each plant into smaller, separate pots. However, I worry this might be too late and cause transplant stress, especially for autoflowers.

I’d really appreciate your feedback and any advice you can offer on this.

Thanks in advance!

PS: The white surfaces on soil are non-woven fabric. After LST, many leaves are touching the soil, which—this is my main concern—is still moist, and I want to prevent mold. Should I remove those leaves? Is it better to remove the older, larger leaves or the younger, smaller ones?

you want your soil to be moist, but drying out in between waterings isn't nessesary.
auto's have a hort life, so you need to stay on top of watering and feeding.
don't chop any leaves off, let them grow, just tuck the leaves in behind the flowering head sites

thanks for reply! I’ve heard that plants thrive with dry–water–dry cycles. Do you think I should really wait until only the top inch of soil is completely dry before watering? I’m worried about overwatering them because it feels like their roots haven’t yet spread throughout the entire pot, so the lower part of the soil isn’t really being used by the plant yet.

What do you think of my plants at day 22? I really like their structure — they’re quite bushy — but they still seem like miniatures, almost scaled down by about 1.5 times.

I’m considering adding one 7W far-red bulb to encourage more stretching. I’d use them alongside daylight on a 20/4 hour schedule. Is that a bad idea?

I don't grow autoflowers, but with photoperiod cannabis not drying quickly enough can be due to too large of a pot and overwatering it or maximally watering it. There can also be a problem when the plant is sick it can cut back on its rate of respiration.

majklsoft said:

I’m worried about overwatering them because it feels like their roots haven’t yet spread throughout the entire pot, so the lower part of the soil isn’t really being used by the plant yet.

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Any given pot size has a water holding capacity, the amount of water it will hold before runoff occurs. A larger pot has a larger water-holding capacity, so if you maximally water that larger pot, it will take longer to dry out.

If roots have not spread throughout the pot, that's another issue, the plant can't uptake water from areas it doesn't have roots.

There's likely nothing you can do right now with those plants, given their limited growing cycle, but you can change your pot sizing on subsequent grows.

simpleleaf said:

I don't grow autoflowers, but with photoperiod cannabis not drying quickly enough can be due to too large of a pot and overwatering it or maximally watering it. There can also be a problem when the plant is sick it can cut back on its rate of respiration.



Any given pot size has a water holding capacity, the amount of water it will hold before runoff occurs. A larger pot has a larger water-holding capacity, so if you maximally water that larger pot, it will take longer to dry out.

If roots have not spread throughout the pot, that's another issue, the plant can't uptake water from areas it doesn't have roots.

There's likely nothing you can do right now with those plants, given their limited growing cycle, but you can change your pot sizing on subsequent grows.

Click to expand...

thank you for opinion. so do you think that this (below) is the best approach for now?

Feed twice a week with the recommended nutrient ratio, but with a smaller volume of water = no runoff. My concern here is the possible buildup of salts in the soil without runnoffs. nutrients are biobizz fishmix, gro, bloom, topmax, calmag.

thanks!

Those are pretty small plants,IIRTC thats a 3.5g pot? if so you dont need to feed every watering.

myke said:

Those are pretty small plants,IIRTC thats a 3.5g pot? if so you dont need to feed every watering.

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The pot is 3.5 gallons with a diameter of 35 cm (13.7 inches). I also think they are small — or better said, small‑proportioned — BUT if they were somehow badly stunted resulting in a slower grow, I don’t think they would develop such nice, strong nodes and side branches. As I wrote above: they feel like cute miniatures.

Do you know what could be the reason? could heavy LST be also a reason?