SoilBible · Episodes · Ep 005

Ep 005: 10x10 FAQ — VPD, Worms, Flushing, pH

· Jeremy runs the first FAQ episode of the 10x10 Season 1 series, answering viewer questions pulled from YouTube and Instagram. Topics cover grow tent environment (VPD-driven temperature and humidity targets), bed sizing inside a tent, max and min plant counts, when and how many worms to add to a no-till bed, whether living organic soil requires flushing, when pH matters for irrigation water, 3x3 bed vs 100 gallon pot, autoflowers under Take-and-Bake, running LEDs at 100% with PAR/DLI as the ceiling, and why a Take-and-Bake pile generally will not go thermal unless you hit one cubic yard. Jeremy's core philosophy throughout: good soil plus good water means you can ignore the pH pen, plant count beats training, living soil never needs flushing, and environment (VPD + DLI) is what determines whether a powerful LED is 'too much'.

Topics

VPD-driven temperature and humidity targets · bed size relative to tent size · plant count vs training philosophy · when to add worms to a no-till bed · flushing living organic soil · pH of irrigation water · 3x3 bed vs 100 gallon pot · Take-and-Bake for autoflowers · running LEDs at 100% with PAR and DLI · thermal composting C:N and moisture · one cubic yard threshold for hot composting · calcium and white ash vs flushing for taste

Sections

0:14 — 1:32

Grow tent temperature and humidity (VPD)

Nicholas Gade asks what the humidity and temperature in Jeremy's tent is right now. Jeremy explains he started at 85 F with 70-75% RH based on the VPD chart, but noticed the LEDs weren't warm enough to kick the exhaust fan on often enough (fan only running once a day). He dropped the setpoint first to 80 F, then to 78 F, which is where it is now with about 65% RH. At 78 F the lights are warmer than ambient so the fan cycles regularly, which in turn triggers the humidifier and keeps fresh air cycling.

  1. 1. Look up a VPD chart (vapor pressure deficit) and use it to pair your temperature with the matching humidity target
  2. 2. Jeremy started at 85 F / 70-75% RH but plants were not as happy as they should be
  3. 3. The problem was that LEDs kept ambient at 84-85 F naturally, so the exhaust fan only kicked on once a day — too little air exchange
  4. 4. Dropped setpoint to 80 F, then down to 78 F
  5. 5. At 78 F with LEDs running, the fan cycles frequently, which triggers the humidifier and keeps fresh air moving
  6. 6. Currently: 78 F, about 65% RH, using the VPD chart as the guide
  7. 7. Edge case: if your grow room lights run hotter, you can ramp temperature up — just keep the VPD chart in mind
1:33 — 1:53

7x7 tent doing the same thing

Okla Grow Me 918 says they have a 7x7 tent running the same thing and plans to order from the site. Not a question but Jeremy thanks them and says a 7x7 works identically to the 10x10, reach out any time.

  1. 1. A 7x7 tent runs on the same principles as the 10x10
  2. 2. Any questions specific to 7x7 can be sent in and Jeremy will answer them
1:53 — 2:04

Favorite tomato varieties

Photosyntax asks what tomato varieties Jeremy likes. He calls out Cherokee Purple as a favorite, classic sweeter heirlooms in general, and Sun Gold for taste.

  1. 1. Cherokee Purple — one of his favorites
  2. 2. Classic sweeter heirlooms in general
  3. 3. Sun Gold — really likes the taste
2:04 — 3:50

5x5 tent — bed size and plant count

Smash Cannabis asks what size bed to put inside a 5x5 and what the max and min plant count is. Jeremy says do not max the bed out to the tent walls — use a 4x4 bed inside a 5x5, leaving 6-12 inches of walk space for airflow and access. A 3x3 inside a 4x4 follows the same logic. A 100-gallon round container also works and gives you a corner to step into. On plant count he says there is no 'max' because the community has a plant-count issue — if you can legally grow more, do more. He'd love to see 16 plants flipped into a 4x4 within a couple days, which gives less veg time, more harvests per year, better quality (because you only take the tops) and less trim work. 90% of the training techniques people use exist only because they are plant-count-limited. Upper limit is one plant per square foot — use the square foot gardening method as a reference.

  1. 1. Size the bed one foot smaller than the tent (5x5 tent → 4x4 bed, 4x4 tent → 3x3 bed)
  2. 2. This leaves 6-12 inches of canopy room around the bed for airflow and ebb-and-flow soil moisture
  3. 3. You can also step in to reach the canopy
  4. 4. A 100 gallon round container is an alternative and gives you a corner to step into
  5. 5. On plant count: do not think in terms of maximum — think in terms of what your plant count allows
  6. 6. Target: 16 plants flipped into flower in a 4x4 within a couple of days
  7. 7. Reason: less veg time, more harvests per year, better quality because you only take the tops
  8. 8. Only taking tops gives better lab quality than forcing lower branches to become tops, and reduces trim work
  9. 9. Upper limit: one plant per square foot (9 in a 3x3, 16 in a 4x4)
  10. 10. Reference: square foot gardening method for plant spacing
  11. 11. Jeremy himself often runs just 4 plants to cover his quadrants because of his own plant count limit
3:50 — 4:46

When to add worms to a bed

Eduardo Lopez asks when to add worms. Jeremy adds worms only after the bed is already set up, moist, and mulched — he'll clear the mulch, throw worms in, and replace the mulch. Never add worms while mixing the soil because you can kill them. He adds only a small handful and lets them multiply according to their own needs. He warns against recommendations from others to add pounds of worms, because that can turn the bed into a worm bin too fast and cause growth problems.

  1. 1. Set the bed up fully and get it moist first
  2. 2. Apply mulch (or be ready to apply it)
  3. 3. Clear a spot in the mulch, drop in the worms, cover back with mulch
  4. 4. Only add a small handful of worms, not pounds
  5. 5. Let them multiply according to their own needs — self-regulation
  6. 6. Rule: never add worms while you are mixing the soil — it can kill some of them
  7. 7. Any time after that is fine — even mid-cycle — so start today
  8. 8. Edge case / warning: adding pounds of worms (as some growers recommend) can turn the bed into a worm bin so fast it causes growth issues
4:46 — 6:43

Flushing living organic soil at harvest

Today Black asks whether you flush this type of soil before harvest or just chop and hang. Jeremy says living organic soil does not need to be flushed. The whole flushing premise — that residual nutrients will sit in the plant and taste harsh — is wrong: plants turn nutrients into more plant material. He explains that the 'white ash' signal tobacco growers chase comes from high calcium content, not from flushing. If you feed heavy right at the end you may chop with mobile nutrients still moving, which can seem slightly harsher — but good curing fixes that. When smoking right away, a bit of fade on the leaves is actually preferable because it means the plant is finishing. In hydro, flushing forces the plant to finish by pulling mobile nutrients from other parts and starting self-decay. In living soil, flushing is irrelevant — you don't flush vegetables you eat, you don't flush herb you smoke. With synthetics there is a valid reason to flush because the plant is overloaded, but living soil never has that problem. Finally, if herb in living soil burns black and tastes harsh, it is almost always a calcium deficiency or a drying/curing problem, not a flushing problem.

  1. 1. In living organic soil there is no reason to flush — you're already mostly water-only
  2. 2. The flushing myth: people believe residual nutrients in the soil will be 'in flow' in the plant and taste harsh — but plants use nutrients to build more plant material
  3. 3. White ash signal comes from calcium content (learned from the tobacco industry), not from flushing
  4. 4. If feeding heavy right at the end, mobile nutrients may still be moving when you chop — curing usually fixes any harshness
  5. 5. When smoking right away, look for a little fade on the plant — fade means the plant is finishing and produces good smoke
  6. 6. In hydro, 'flushing' just means stopping nutrients — the plant translocates mobile nutrients from other parts and begins to decay itself
  7. 7. With synthetics there can be a reason to flush because the plant may be overloaded; living soil never has that condition
  8. 8. We don't flush vegetables we eat or herb we smoke — we grow them properly
  9. 9. Edge case: if your living-soil herb burns black or tastes harsh, the cause is almost always a calcium deficiency or a drying/curing problem, not a flushing problem
  10. 10. Fix the whole process — grow, dry, cure — not just one piece
6:43 — 8:47

pH of irrigation water

Pew Pew asks whether to pH water or pH teas before applying them if they run acidic or basic. Jeremy says he does not pH at all, but the caveat is that he uses clean filtered water. If you use well water, ditch water, or you are farming on acreage you MUST test the water, because you may already be getting calcium or magnesium from it, and the water may be alkaline either from high pH or from high bicarbonate alkalinity. On alkaline acreage (orchards), growers pH the water with acid — but what they are really doing is binding the bicarbonate so it stops locking up the calcium in the soil. With good soil and good water, pH is out the window. With good soil and bad water, clean the water and pH only if necessary. About 90% of home growers have clean water and do not need to worry about pH at all. What actually matters is the pH of the soil, which is set by the recipe and order of nutrients. Pouring zero ppm water into good soil will not drastically affect soil pH — the microbiology will. But pH-ing water and then flushing 100 gallons through a 10 gallon pot WILL adjust the soil pH because you are leaching nutrients out, and it is the nutrients in the soil that make the pH.

  1. 1. If you have clean filtered water and good soil — do not pH, ignore the pH pen
  2. 2. If you use well water, ditch water, or you are farming acreage, test your water first
  3. 3. Water can already contain calcium or magnesium — you want to know that
  4. 4. Water can be alkaline two ways: high pH, or high bicarbonate alkalinity
  5. 5. On alkaline acreage (orchards), the real purpose of 'pH-ing the water' is to add acid that binds the bicarbonate so it stops locking up calcium in the soil
  6. 6. Decision tree: good soil + good water → no pH needed. Good soil + bad water → clean the water, pH if necessary
  7. 7. 90% of home growers with good clean water do not need to worry about pH at all
  8. 8. What actually matters is the soil pH, which is set by a good recipe and the proper order of nutrients
  9. 9. Pouring zero-ppm water into good soil will not drastically shift soil pH — the microbiology will
  10. 10. Warning: flushing 100 gallons of pH-ed water through a 10 gallon pot WILL leach nutrients out and shift the soil pH — because it is the nutrients in the soil that make the pH
8:48 — 9:07

3x3 bed vs 100 gallon pot

Courtney Dye asks if there's any advantage to using a 3x3 bed over the 100 gallon pot Jeremy cooked his soil in. Jeremy says there's no performance advantage — the 3x3 just comes with a built-in PVC trellis frame and is square. You can build a square trellis around a round 100 gallon just the same. Some people like the 3x3 because it looks tighter and neater. What actually matters is the volume of soil under the grow light — the more, the better.

  1. 1. The 3x3 bed has no performance advantage over the 100 gallon pot
  2. 2. Difference: the 3x3 has a built-in PVC trellis and is square
  3. 3. You can build a square trellis around a round 100 gallon with no problem
  4. 4. Some growers prefer the square shape because it feels tighter and looks neat
  5. 5. What matters: volume of soil under the light — the more, the better
9:07 — 9:58

Take-and-Bake for autoflowers

Kin Knife asks whether it makes sense to use Take-and-Bake for small spots and autoflowers, since living soil takes time to activate and autoflowers have smaller grow windows. He wants to jump from bottled nutrients. Jeremy says yes — Take-and-Bake doesn't take that much time, and autoflowers interact with soil the same as any other plant. The risk with autoflowers is stunting: you cannot wait for them to recover before flipping, because they flip on their own clock regardless of photoperiod. Any over- or underwatering hits yield harder on autos because you have no control over the timeline. Most autoflower growers running living soil use 4-5 gallon pots and treat them with as much care as possible. Take-and-Bake is the perfect soil for that and should give better autoflower results than anything they've grown before.

  1. 1. Yes, Take-and-Bake is appropriate for autoflower small spots
  2. 2. Take-and-Bake does not take that much time to activate
  3. 3. Autoflowers interact with soil the same as photoperiod plants
  4. 4. Critical difference: autoflowers flip on their own clock — you cannot wait until they are healthy to flower them
  5. 5. Stunting matters more with autos because any over- or underwatering hits yield with no recovery window
  6. 6. Most living-soil autoflower growers use 4-5 gallon pots
  7. 7. Treat autoflowers with as much care as possible — no stunting, steady moisture
  8. 8. Take-and-Bake is the perfect soil for autos and should outperform bottled-nutrient results
9:58 — 10:28

Follow BuildASoil-style growers on Instagram

Jeremy moves to Instagram questions. Watch It Bud said 'just tell them my page is built on the BuildASoil way.' Jeremy uses this as a prompt to recommend following many of the no-till growers on Instagram — there are thousands doing this now, so there's no shortage of technique to learn from.

  1. 1. Follow BuildASoil and other no-till growers on Instagram to 'steal their tech'
  2. 2. There are thousands of growers running this system now
  3. 3. You should have confidence this system works — start today
10:28 — 11:08

Sexing plants under a T5 before the next run

The Stone Baker grows in a small space and wants to start the next run under a T5 to save time. He's asking how to sex the plants — clone and sex the clone, or sex the parents, or can he make parents show without flipping the light cycle. Jeremy says all of the plants currently on camera are actually already sexed — they've been running under 18 hours of light and he has done nothing special. They are at the point where he'd now be able to clone them. If cloning-to-sex is the plan, you'd have to either take very small clones or take them a while earlier to catch up. He says he'll show the exact sexing and cloning technique in upcoming episodes.

  1. 1. Running 18 hours of light, the plants will actually sex themselves — no special trick needed
  2. 2. At that point, the parents are also right around the window to clone
  3. 3. If you want to clone-to-sex, either take very small clones or take them earlier so they have time to catch up
  4. 4. Exact technique will be shown in upcoming episodes
11:09 — 12:35

Running LEDs at 100% — PAR and DLI

Mirvatronicus asks whether Jeremy ramps lights up from germination through flower or runs 100% from the start. Jeremy explains that the new big-panel LEDs are hard to lower and adjust, so for schedule-simplicity he runs them at 100% all the way up at the top of the tent and uses a PAR meter to read the average at canopy. Current reading is around 500 PAR. He mentions the previous video on DLI (daily light integral), which sets the minimum and maximum light budget across the daily grow period. The only downside of running 100% at the top is wasted electricity — he could dim the light, drop it closer to the plants, and get the same PAR. But he's busy. The real lesson: if your light seems 'too potent' it isn't about running at 100, it's about whether the environment (VPD + DLI) matches. At 100% over 18-20-24 hour photoperiods with plants too close, these LEDs can be too much — watch the DLI video.

  1. 1. Jeremy's new big-panel LEDs are hard to dim or adjust precisely
  2. 2. For schedule simplicity: mount them at the top of the tent and run 100%
  3. 3. Use a PAR meter to measure average PAR at the canopy
  4. 4. Current reading: around 500 PAR at canopy
  5. 5. Reference the DLI (daily light integral) — it sets both minimum and maximum light across the daily photoperiod
  6. 6. Caveat: running at 100% at the top of the tent wastes some electricity — you could dim and bring the light closer for the same PAR
  7. 7. If the light seems too potent for the plants, the real problem is an environment mismatch (VPD and DLI), not the 100% setting
  8. 8. Warning: these LEDs at 24 hours, 20 hours, or even 18 hours on 100% can be too much if plants are too close — watch the DLI video
12:36 — 14:01

Thermal composting and Take-and-Bake moisture

Mojo Jojo 20 asks whether under-watering soil from episode 3 could cause it to heat up — noting Jeremy mentioned dry spots during the remix. Jeremy explains moisture matters in compost because if the carbon-to-nitrogen ratio is correct, a compost pile will go thermal — and poor moisture can prevent it from going as hot as it should. But if the C:N ratio is right, even slightly over- or under-wet compost will still go hot. The key threshold is volume: a cubic yard (3x3x3 feet, 200 gallons, 27 cubic feet) is where you get enough energy in one place to generate thermal activity. A single Take-and-Bake kit is nowhere near that. Three Take-and-Bake kits mixed as one pile would be 27 cubic feet and might actually go hot. The other trigger for going hot is doubling the nutrients. So one Take-and-Bake kit is totally safe from thermal activity regardless of moisture — but it's good to know the mechanics in case anything ever does go hot on you.

  1. 1. Moisture is important in compost — lesson learned from making real compost piles
  2. 2. If C:N ratio is correct, a pile will go thermal (hot)
  3. 3. If moisture is wrong but C:N is correct, it will still go hot — just not as hot as it should
  4. 4. Threshold for thermal activity: 1 cubic yard (3x3x3 ft, ~200 gallons, 27 cubic feet) of material in one spot
  5. 5. A single Take-and-Bake kit is far below the 1 cubic yard threshold
  6. 6. Three Take-and-Bake kits combined = 27 cubic feet = 1 cubic yard — could go hot if mixed as one pile
  7. 7. Other trigger: doubling the nutrients in any mix could cause it to go hot
  8. 8. Conclusion: a single Take-and-Bake kit is totally safe from thermal heating regardless of moisture
  9. 9. Good to know the mechanics anyway so you can recognize it if something ever does go hot
14:02 — 14:56

More FAQs coming across the series

Jeremy wraps up saying he got more questions than expected, so he'll save the rest and sprinkle them into upcoming episodes — especially during the late-flower stacking phase when there's less hands-on work. For urgent questions, viewers can use live chat at BuildASoil.com, Instagram DMs, or YouTube comments.

  1. 1. More questions came in than could fit in one episode
  2. 2. The remaining questions will be answered across the next 8-10 weeks
  3. 3. Late flower (stacking) has downtime, which is a good time for Q&A
  4. 4. For urgent questions: live chat at BuildASoil.com, Instagram DM, or YouTube comments

Notable quotes

"so check out a VPD chart — that'll give you a temperature and humidity to shoot for"

Jeremy's answer on tent environment, reducing the whole question to 'look at a VPD chart'

"I don't want you to max it out to the walls — we need air space around there"

On bed sizing inside a 5x5 tent

"90% of the practices you see — a lot of the training — it's all because we can't grow enough plants"

Jeremy's core thesis that plant count, not training skill, is the real limiter

"I only add a few worms, maybe a small handful, and I let them multiply according to their own needs"

Jeremy's worm self-regulation approach, in contrast to 'pounds of worms per bed' recommendations

"in living organic soil there's no reason to flush, for the most part we're pretty much doing water only"

Jeremy's core answer on flushing

"we don't flush our vegetables that we eat, we don't flush our herb that we smoke"

Jeremy's philosophical framing of why flushing does not belong in living soil

"if your herb is too dark in living soil, it's burning black, it tastes harsh — usually it's just because there was not enough calcium"

Jeremy's diagnostic for harsh smoke in living soil — calcium, not flushing

"90% of home growers that have good clean water, they just don't need to worry about pH"

Jeremy's stance on pH for home growers

Glossary terms from this episode

Alkalinity · Autoflower · Bicarbonate · Carbon to nitrogen ratio (C:N) · Clean filtered water · Cubic yard threshold · DLI · Fade · Flushing · Mobile nutrients · No-till bed · PAR · pH of soil · Photoperiod plant · Plant count · Sexing (under 18 hours of light) · Square foot gardening method · Take-and-bake kit · Thermal composting · VPD · VPD chart · White ash · Worm self-regulation

Products mentioned

PAR meter · BuildASoil Take-and-Bake Kit · Grow Tent Humidifier · 10x10 grow tent · VPD chart · Grow tent exhaust fan (controller-driven) · 4x4 bed inside 5x5 tent · 3x3 bed inside 4x4 tent · 100 gallon round container (fabric pot) · 3x3 bed with built-in PVC trellis · 4-5 gallon pot (for autoflowers) · Big-panel LED grow light (new generation) · T5 fluorescent grow light · BuildASoil live chat · BuildASoil Instagram DM · Worms (small handful for no-till bed) · Mulch (bed top cover) · Water filter (for clean irrigation water) · Acid (for acreage water treatment) · pH pen