PH Question.....

[green as grass]

Will adding Lime have any knock on effects? It may balance pH but then cause other problems?

i know the lime will add calcium and other minerals so i dont think so.

 

[andytoker]

flushing (as in putting loads of water through the soil) is pointless with organics and just gives you very wet soil and problems associated with that.

best to add dolomite lime to the soil mix at 5g per litre of soil. needs to be mixed in to the soil before you start. humus also buffer the pH so you want some good compost/EWC or similar

hydrated lime will raise your pH higher than 7 and is not usually a good idea.

you want to make sure your water source isnt way off - between 6 and 7 is good. if not then adjust it with citric acid to around 6.

measuring the pH of runoff doesnt really tell you anything about organic soil. it's totally different to using chem ferts. ive done many successful organic grows and never measured my runoff once.

A.

 

[green as grass]

flushing (as in putting loads of water through the soil) is pointless with organics and just gives you very wet soil and problems associated with that.

best to add dolomite lime to the soil mix at 5g per litre of soil. needs to be mixed in to the soil before you start. humus also buffer the pH so you want some good compost/EWC or similar

hydrated lime will raise your pH higher than 7 and is not usually a good idea.

you want to make sure your water source isnt way off - between 6 and 7 is good. if not then adjust it with citric acid to around 6.

measuring the pH of runoff doesnt really tell you anything about organic soil. it's totally different to using chem ferts. ive done many successful organic grows and never measured my runoff once.

A.

in your organic grows were you using dolmite lime?

 

[green as grass]

Agricultural lime (not hydrated lime) should be added at a rate of 1 cup per cu. ft. of soil. Or 1 tablespoon per gallon of pot. This helps raise pH and offset the lowering caused by the salts in the fertilizer. I use promix and water with 6.1-6.2 pH water. My r.o. water is always between 5.8-6.0. You want your run-off in the 6.7-6.8 area........ the pro-mix medium naturally turns acidic over time so it helps to raise your pH level slightly when you are later in flowering.

is agricultural lime-Dolomite?
what are the differences

 

[SSHZ]

Yes, dolomitic lime is the same as agricultural lime. It's slow release, that's the key. DO NOT use hydrated lime for this purpose. Hydrated lime can be used as a quick fix in small amounts but is not needed if you applied dolomitic at the start.....

 

[mrcharli3]

and flooding organic soil will cause anaerobic beasties and suffocate the root's and good beasties. just make sure the solution is adjusted before adding....if you see a lock out then check run off but if you are using a good mix and not over feeding there really should be no need to even measure the run off and even flush at all...i will probly catch some heat but seriously vic's and sub's "super soil" are trouble free!! get in tune with the plant and your mix! don't try pushing them with over feeding it will do more harm than good but if it's not from that than re-think the mix add some dolomite to raise it or peat to lower it..hard wood ashes also raise ph and add K but becareful with them. a good mix will balance it self.that is the whole idea

 

[andytoker]

in your organic grows were you using dolmite lime?

sorry for the late response

yes 5g dolomite lime for every litre of soil used. helps buffer pH and adds calcium and magnesium. you need powdered dolomite lime. not the same as regular garden/hydrated lime.

 

[dirtysOrganics]

quick question.......

im gettin my nutrient mix @6.3-6.5 every time. but the soil keeps reading 6.9-7.0. the runoff is at ok levels but whats up with the dirt? why so much higher? what do i do? using fox farm ocean forest.

 

[andytoker]

the pH of your waterings/nutrient solution doesnt have that much influence on the pH of a good organic soil. im no expert on FFOF but i believe it contains lime or oyster shells - also to buffer pH.

what do you do? - if your plants look happy then do nothing :) = or keep doing what you're doing

as i said above, unless your water supply has high alkalinity then you shouldnt need to worry about pH when using a good organic soil.

 

[Misterdirt]

I agree with many of the responses here. To explain what people are seeing in the pH difference between the watering solution and the runout water at the bottom of the pot:

Soils have what is called BUFFER CAPACITY. Soils high in organics have a higher buffer capacity than mineral soils (except for some high clay soils). Part of the buffer capacity comes from the organic matter itself. Active carboxyl and phenol groups in the organic matter hold extra cations, which include many that affect pH. Another part comes from the amount of agricultural lime mixed in the soil. Ag lime (CaCO3 and dolomitic limestone) is only slightly soluble. When acidic water is added, a little of it dissolves, and neutralizes the acid. That's why the runout at the bottom of the pot has a different pH.

Buffer capacity is a good thing. It prevents drastic soil chemistry changes that can shock plants. It is the reason soil is less hassle than hydro. It is the reason soil can hold certain nutrients (K, Ca, Mg and many of the metallic micronutrients).

If your pH is between 6 & 7, I wouldn't worry about it. 6.5 is ideal, but going to extremes to achieve it is a waste of your time, if it's pretty close.

Fox Farms OF does have a lot of crushed oyster shells in it, which is the same as limestone/ag lime/CaCO3. From my experience, it will maintain a pH between 6.4 and 7.0 for an entire grow. (Also from my experience, it's a little too strong for some sativa doms, resulting in leaf tip burn, unless you mix it with something else.)

Using 'quick lime,' or hydrated lime, or CaO should not be done on soil with live plants in it. It dissolves readily, can put way too much Ca into the soil at once, raises pH very fast and can also burn your hands as well as plant tissue. It has a strong exothermic reaction when it combines with water and dissolves. Roots can be literally cooked.

 

[tortuga1503]

great info mrD

 

[jakew215]

i feed/water from the bottom.

how would i test my runoff?

and did i see someone say its bad to flush soil with a lot of water??? really?

 

[Misterdirt]

i feed/water from the bottom.

how would i test my runoff?

and did i see someone say its bad to flush soil with a lot of water??? really?

If you think pH is a concern, go from the top next time you water. If your plants are happy, you may not want to bother.

How do you flush if you don't water from the top?

 

[jakew215]

If you think pH is a concern, go from the top next time you water. If your plants are happy, you may not want to bother.

How do you flush if you don't water from the top?

i just run 3x(of container size) the amount of water through the container a few times the last couple weeks. the reason i feed/water from the bottom is i think it helps to make the roots reach for the bottom of the pot, instead of like up and to the sides. idk though, just my stoner thoughts. then if i were to run water through the top after doing it from the bottom i really wouldnt get an accurate reading on what the plants are seeing. idk though, sorry im just being argumentative lol.

 

[Misterdirt]

You can't measure exactly what your plant roots are seeing. The best you can do is correlate what you can measure with how well the plants are doing.

But when my plants are looking happy, I don't go searching for reasons why they should be unhappy. That's one of the main reasons I grow in soil.

 

[Dorje]

I know this started a while ago but I'd like to add that the advise to flush is horribly wrong.

Mr. Dirt gave a good explanation.

Bottom line, feeding with organic ferts in the pH range of around 4 is fine if you have soil that has some pH buffering from lime. All potting mixes come with a buffer but some need more, and if you re-use your soil (which you should!) you will need to add more lime in between runs.

If you do have a buffered soil and adjust your pH up to 6.5 from 4, you will add more alkaline material to your soil than is needed and the pH of your soil will eventually rise ABOVE NEUTRAL. Mr. Dirt gave a good explanation of why this happens, so read it again if you need to. This is really a key point to understand with organics.

 

[mrbong73]

I wanted to share some information posted by an extremely knowledgable person on another cannabis forum. This is strickly copy and paste. Thanks to LumperDawgz.

"Oh dear! The dreaded 'PH' discussion relative to organic growing!

Here goes - many organic growers start either building their own soil from the ground up, i.e. buying peat or coir, one, all or any of the following: perlite, pumice and vermiculite. Some dolomite lime (to neutralize the peat moss PH) and some kind of a wetting agent. From there you add your compost or earthworm castings which will be PH neutral (assuming that you're using compost which has been correctly made), seed meals or bloodmeal for the 'N' deal and bonemeal or fish bone meal for the 'P' deal. And some type of rock dust.

None of these soil amendments will cause a change in the potting soil's PH.

If you start out with a professional soilless mix like ProMix or Sunshine Mix, these products are made for the nursery industry. Their mixes are adjusted for a neutral PH at the packing shed.

The humic acids in compost (and earthworm castings) neutralize the PH in the soil meaning that even if you add a tea in the PH range of 4-9, these acids keep things in check.

I know that this flies in the face of conventional cannabis growing because much of the information comes from the hydroponic side of things that got transferred over to soil growers.

There's a plethora of information about PH and organic farming so that you can make up your own mind. "

 

[plantevil]

if u have bad soil... like to much manure in your soil (happened to me b4) and no dolimite lime for an adjuster its almost impossible to get the ph down. u can flush till kingdom come with very low ph water and u might get it to come down a smidge but as soon as u feed it goes right back up and locks the plant. i for real had to flush heavily after every single feeding just to prevent complete lockout. when your running a decent sized operation thats ALOT of work but it did work and i had a very good outcome.