Potting soil and ph

Outdoor Growing
#1

So, I realize ph is an important factor in growing, but I honestly have not seen anything but minor changes in my outdoor soil and grows. I use my regular tap water which in Los Angeles is crazy acidic… in the low 5’s… Unless you are working in the straight dirt in your yard or some guerilla grow somewhere, I just don’t see my soil ph changing one way or the other in any substantial way from my fertilizer, tap water or bagged potting soil.

I see it’s everyone’s first go to when trying to assess someone’s problem childs, but to me when it’s in soil I just have yet to see it in action. I went outside and ph checked my oldest and newest plants soil (all bagged potting soil) and they all are within 6.8 to 6.9. The soil from two weeks ago was equivalent to my 2 month old soil. I’ve read all the lit about ph, but can someone explain to me what you would have to do to potting soil to really screw up the ph that’s within the everyday normal watering and fertilizing?

5 Likes
#2

I’d like to know this as well. Definitely something I want to know. I don’t even get a pH change in my soil period. I’ll test it and eat my words in a bit if I spoke too soon, but my soil pH seems locked at 6.5 no matter the fertilizer. It was the same after I switched to megacrop and it was the same when I added the miracle gro that tested at pH 5 at the concentration I was using. The soil before I even added any fertilizer was also always 6.5. I tested daily for 2 weeks. Drove myself insane thinking it could swing without warning. After that I tested once a week. I stopped testing in mid August when I had 1 pH tester capsule left. I think it’s enough time to see if anything has changed or if I’m still at a constant 6.5 pH.

I’ve tested both completely dry topsoil and even dug down a bit to get some soil from below. I’ve tested immediately before watering, immediately after watering, after a few hours post watering, and Midway through my first time drying out the soil when I switched to 12/12. Every time it was always the same pH. I’d definitely like to know what’s up there

4 Likes
#3

ph matters more in hydroponic-type setups… soil has a lot of buffers which let it maintain a relatively stable ph value if it’s mixed right. In hydroponic/aeroponic/etc… type setups though, you only have the nutrient/water mix, and if your ph is wrong, it’s extremely easy to nute burn or lockout nutrients. Not saying you can’t mess ph up in soil (done it), but it’s a lot harder to do.

5 Likes
#4

Today was the first time I’ve tested my potting soil ph since my first batch of plants. I jacked up that first grow too with overwatering and overnuting and that soil ph never went above 7 either. If I amended the actual dirt from my garden (living soil) and not potting soil, I could easily see ph being thrown off, but I really don’t see it in potting soil.

1 Like
#5

I would think you would have to add a lot of time released nutes or throw some sulfuric acid in there to really see an issue in potting soil. Imho

2 Likes
#6

In soil it is buffered by the soil and the microorganisms that reside within
In hydro you are the only control
A lot of this PH malarky is a hang up from hydro growers and mis-info to a degree.

There are times your soil can get out of whack:

  • if its poor mix to start with (think homemade)
  • if you re-use for years the calciums etc compost manufacturers use can be used up
  • if your using cheap chemical fertilisers (good ones are PH buffered)
  • If you over fertilise and cause chemical salt build up, can create PH issue due to chemical reactions and “lockout”
7 Likes
#7

Often it is said, measure the pH of the water / food you are adding. Check the soil from time to time and don’t bother with the run-off.

A couple of folks in front of me have their hands on the issue. Soil, even store bought soil, has buffers which tend to stabilize the pH.

Add a bunch of lime to your store bought soil and watch what happens. Lime will buffer the pH up.

6 Likes
#8

I’m guessing it’s your crazy acidic water that’s kept you from seeing what my 7.2 hexavalent chromium water does.

I never find dirt below 7 here.

Most foliage here is a bit pale.

:thinking:

potting media & outdoor dirt are different animals too.

:evergreen_tree: hmm. c’mon orchid theory

3 Likes
#9

Not that I know a lot about water chemistry and water PH but I do know Ph is logarithmic meaning that a ph of 7 is considered neutral however a ph of say 6 or 8 is 100 more acidic/basic respectively and when it drops to 5 it’s 1000 times more acidic and 1000 x more basic when at 8. So like they say I’m the above comments you really have to screw things up major when working with soil because of ph buffers water on the other hand is a different story say your working with a liter of water that neutral and your adding phosphoric acid and ya add like 5 ml all of a sudden it’s at like 3 ph and you just killed your plants at the blink of an eye! Lol hope that helps explain a little better!

6 Likes
#10

I rarely check runoff pH anymore. My plants are in 5 gal fabric pots of potting mix and I have to feed >1 gal, before I get any runoff. I don’t like to over-water 'em. When I have checked, it’s 5.9 pH in, runoff is 6.2 - 6.3 pH. I don’t think about it much unless the plants are displaying symptoms.

1 Like
#11

my tap water is between 8.4-9 here and soil is 7-8
my best plot last year is where pines are dropping *some needles
might have to start adding pine needles to my beds and see if it can help

maybe I should be using acid loving plant ferts?
just reading about sulphur to change garden ph

1 Like
#12

Ya pine needles will definitely make soil more acidic over time just keep an eye on that soil ph may have to add lime at a later date if swings to low

1 Like
#13

I’ve tried sulfur and it’s ridiculously slowwwwww. :snail:

So slow that I just said 'fuggit and threw a few unripe oranges in a blender & mixed it to a bag of soil mix… it smelled great, heated :fire: up, and grew a lot fungal :mushroom: hyphae… the pH dropped to about 4.something :smile: and i think i just threw it in a much larger soil pile.

fingers crossed, my orchid mix experiment should do the trick…

:evergreen_tree: arboreal orchibis

4 Likes
#14

yeah it says sulphur can take months
didnt mention if you can add it to a bed with plants in?

#15

here’s the product i have used; it takes about a year or more to drop 1 pH point +.
in an indoor container it took even longer. :thinking:

https://www.espoma.com/product/soil-acidifier/

:evergreen_tree:

2 Likes