Dolomite Lime

Joe parker

Joe parker

Active Member
I'm growing 8 autoflowers in 2 gallon smart pots with FFOF soil. About 4 weeks in I noticed yellowing of the leaves so I tested the soil ph and it was ~5.8 in all the plants. I always ph my water to 6.5 before adding it to the soil. I flushed and flushed the plants with 6.5-6.8 water and could only get them to a ph of 5.9-6. I looked for ways to raise ph safety and people suggested top dressing powdered dolomite lime into the soil to buffer ph. They all said 1-2 tablespoons per gallon of soil. I only added 2 tablespoons per pot of soil, scratched it into the top of the soil, and did regular waterings. The plants seemed to do better for 2 weeks but now they're all yellowing and all the soil ph is around 8. My question is why do people recommend that much lime per gallon of soil when it's clearly to much?
 
C

churchhaze

Well-Known Member
Joe parker said:
I'm growing 8 autoflowers in 2 gallon smart pots with FFOF soil. About 4 weeks in I noticed yellowing of the leaves so I tested the soil ph and it was ~5.8 in all the plants. I always ph my water to 6.5 before adding it to the soil. I flushed and flushed the plants with 6.5-6.8 water and could only get them to a ph of 5.9-6. I looked for ways to raise ph safety and people suggested top dressing powdered dolomite lime into the soil to buffer ph. They all said 1-2 tablespoons per gallon of soil. I only added 2 tablespoons per pot of soil, scratched it into the top of the soil, and did regular waterings. The plants seemed to do better for 2 weeks but now they're all yellowing and all the soil ph is around 8. My question is why do people recommend that much lime per gallon of soil when it's clearly to much?
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Because it's hard to know how much lime is enough. Recently, people have been putting in way too much. Does that answer your question? :joint:
 
Joe parker

Joe parker

Active Member
churchhaze said:
Because it's hard to know how much lime is enough. Recently, people have been putting in way too much. Does that answer your question? :joint:
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Is there any way to fix it and not have my plants die, they only have 3 weeks left of flowering or am I SOL?
 
past times

past times

Well-Known Member
any pictures? I would just go back to my normal at this point. Some of the lime will flush out over the next couple waterings. Slow changes are better then abrupt ones for the plant.
 
TubePot

TubePot

Well-Known Member
I have a 1 bag recipe of Super Soil that calls for 2 tablespoons of Dom Lime, so 2 tablespoons per pot is way to much.
 
A

az2000

Well-Known Member
A photo would help. Autos tend to die off at the end of life (more than photos do). Could be you reduce N too much which is also another popular thing to do in flower.

For me, soil ph of 5.8 isn't bad. I doubt your problem has anything to do with ph. (Remember, ph rises as the soil dries. Even though 5.8 may seem too low for uptake of some nutrients, it will rise to 6.8 if you let it dry thoroughly.). I don't have problems until it goes below 5.4. This correlates to a runoff ppm of 2400. If it gets above 2500, the ph will go to 5.2 and lower, which is where problems start for me.

If you thought you had acidic soil I'd encourage you to flush. But, 5.8 doesn't sound bad. (Do you feed with a lot of runoff? If so, you should be in good shape.).

So, I think it's just that you reduced N too much (too soon) in flower. And/or the nature of autos to die off. A photo should always be provided when asking about a problem like this. It sounds like it started awhile ago. If you have photos showing earlier examples, that would be good.
 
green_machine_two9er

green_machine_two9er

Well-Known Member
Dolomite lime is powerful stuff. But. I'm guessing you have a lockout of Mg Or ca. Increased amounts lock each other out im pretty sure.Pics would help. ffof already has plenty of dolo lime in it. I'm not sure how to remedy your situation. Straight water and hope for the best?
 
Jimdamick

Jimdamick

Well-Known Member
Joe parker said:
I'm growing 8 autoflowers in 2 gallon smart pots with FFOF soil. About 4 weeks in I noticed yellowing of the leaves so I tested the soil ph and it was ~5.8 in all the plants. I always ph my water to 6.5 before adding it to the soil. I flushed and flushed the plants with 6.5-6.8 water and could only get them to a ph of 5.9-6. I looked for ways to raise ph safety and people suggested top dressing powdered dolomite lime into the soil to buffer ph. They all said 1-2 tablespoons per gallon of soil. I only added 2 tablespoons per pot of soil, scratched it into the top of the soil, and did regular waterings. The plants seemed to do better for 2 weeks but now they're all yellowing and all the soil ph is around 8. My question is why do people recommend that much lime per gallon of soil when it's clearly to much?
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Because they don't know what the fuck they are talking about. Dolomite lime HAS to be added and mixed into the soil BEFORE planting, if is not done that way and placed simply on top of the soil, it is basically useless. What should be used in a situation like yours is Hydrated lime, which dissolves in water, and will penetrate the entire pot, and the effect is immediate. Dolomite takes day's, if not weeks as a top dressing, plus it will cook your plant if too much is given. 2 gallon pots are small anyway, go to a Garden store, get a 3 gallon, repot, and you should finish ok.
 
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az2000

Well-Known Member
green_machine_two9er said:
Clones? Or from seeds. ? Established plants with a rootball already.? Just curious
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I only grow from seed. I haven't been pleased with my sprouting and just tried rapid rooters started in the soil (not a tray, just let the roots grow into the soil). I liked it better. The difference isn't great. But, they seemed 20% more vigorous to me. I felt it had more to do with a uniform texture and pressure against the seed, better drainage/aeration.

The only benefit I can see from letting dolomite "cook" is if the soil's initial ph is off. It takes about 10 days for dolomite to react and move ph. I could see that being undesirable not only because the soil ph would be off during that period, but the reaction may release more ca and mg than is healthy for a seedling.

For me, it starts at 6.2-6.3. Not much reaction to occur during those 10 days.
 
calicocalyx

calicocalyx

Well-Known Member
I have yet to see too much dolomite ruin a plant. I think it is dependent on how acidic the soil is to break down. Top dressing is fairly inefficient though, makes more sense to use hydrated however I haven't done this as it's usually prescribed with a load of caution. Humic acid is good to use in combo with a flush, I think I read that it helps grab those nutes. Flushing alone should do the trick though. I wouldn't stress them too much if they are flowering.
 
A

az2000

Well-Known Member
calicocalyx said:
Top dressing is fairly inefficient though, makes more sense to use hydrated however I haven't done this as it's usually prescribed with a load of caution.
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I agree. When I had acidic soil I corrected it with hydrated lime. It didn't take 10 days like dolomite does. Using hydrated lime attracts a lot of naysayers. I'm reluctant to ever mention it. It definitely requires careful use because it's so strong and phytotoxic. But, it is the way to correct an unanticipated problem.

I've only used it in two grows until I figured out my problem. I think it's perfectly valid to fine tune the starting ph of a soil (1/4 tsp amended into a gallon of soil will raise the ph about 0.3-0.4) or treating a problem in the middle of a grow. But, dolomite and feeding a proper amount of nutes (and/or have lots of runoff) is better to have *stable* ph.
 
calicocalyx

calicocalyx

Well-Known Member
az2000 said:
I agree. When I had acidic soil I corrected it with hydrated lime. It didn't take 10 days like dolomite does. Using hydrated lime attracts a lot of naysayers. I'm reluctant to ever mention it. It definitely requires careful use because it's so strong and phytotoxic. But, it is the way to correct an unanticipated problem.

I've only used it in two grows until I figured out my problem. I think it's perfectly valid to fine tune the starting ph of a soil (1/4 tsp amended into a gallon of soil will raise the ph about 0.3-0.4) or treating a problem in the middle of a grow. But, dolomite and feeding a proper amount of nutes (and/or have lots of runoff) is better to have *stable* ph.
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I used heaps of dolomite, like 2 cups in 20 gallon pots. It took 10 days ish, after a flush to fix the problems, but didn't give me new ones. Like everything there are lots of variables to contend with. I didn't just flush and add dolomite, I also discovered I had too much calcium in the water and even cal/mag straightened it out but have switched to just epsom salts and proper watering/ferting ( i.e. don't underwater/overfert ). I could push a little harder with better water but my ppms are too high in the winter.
 
Joe parker

Joe parker

Active Member
This week I tested all the runoff and they're all between 6-7 so I'm guessing the dolomite I added raised the soil ph to high and then buffered itself back down. I defiantly used to much though because for a week or two I couldn't fix ph and it stunted my autoflowers and killed off a lot of foliage. image.jpg
 

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