What's new
  • ICMag with help from Landrace Warden and The Vault is running a NEW contest in November! You can check it here. Prizes are seeds & forum premium access. Come join in!

This is why the pH of your organic soil matters

C

Carl Carlson

Lowenfels, Jeff & Lewis, Wayne. Teaming with Microbes. Portland: Timber Press, 2010.

pg. 42:

Why is pH a consideration when we talk about the soil food web? The pH created by a nutrient-ion exchange influences what types of microorganisms live in the soil. This can either encourage or discourage nitrification and other biological activities that affect how plants grow. As important, each plant has an optimum soil pH. As you will learn, this has more to do with the need of certain fungi and bacteria important to those plants to thrive in a certain pH than it does with the chemistry of pH.​

pg. 110:

Two forms of nitrogen are available to plants when there is a healthy soil food web, nitrates and ammonium (NH4); and - as in most things in life when there is a choice - some plants prefer their nitrogen as nitrates while others prefer ammonium.

When nematodes and protozoa consume fungi and bacteria, nitrogen is released in ammonium form in the waste stream. Ammonium is quickly oxidized or converted to nitrates by nitrogen-fixing bacteria when they are present in sufficient numbers in the soil. The is almost always the case when the soils are dominated by bacteria as compared to fungi because the slime produced by soil bacteria has a pH above 7, the right environment for nitrifying bacteria. In bacterially dominated soils, nitrifying bacteria generally thrive.

Fungi foster lower pH numbers because they produce organic acids to decay organic matter for nutrients. If there are enough fungal acids to offset the bacterial slimes, the soil's pH drops below 7, making the environment acidic and therefore more suitable for most nitrifying bacteria. More ammonium remains ammonium.​

pg. 111:

...most vegetables, annuals and grasses prefer their nitrogen in nitrate form and do best in bacterially dominated soils.​

pg. 113:

If you are a vegetable gardener, you need to aim for a biomass that has slightly more bacteria than fungi. More specifically carrots, lettuce broccoli, and cole crops prefer an F:B of .3:1 to .8:1; tomatoes, corn, wheat go for an F:B of .8:1 to 1:1.​
 
Zendo

Zendo

Member
I think what confuses people on here most of the time is that many of us say 'ph doesn't matter, don't worry about it''

But, we are really saying, 'as long as you build a good healthy soil food web, and feed balanced foods and soil builders, that you don't need to worry about ph, as it will be taken care of naturally, as it should be.'

I know this to be true, as I build my own soil mix, and feed it teas, and never ever ever for any reason check the ph/ppm/etc and I produce great flowers with good yields.

The key is to create a healthy soil food web, feed that web appropriately, and stay out of the way so that the plants can do what they do best.

ymmv.
 
E

EatMoGrass

Member
Great explantions guys! Close counts when it comes to ph of living organic soil. As long as it is in the mid-high 6 range the microbes should be happy and everything needed for veggies/cannabis should be available.
 
C

Carl Carlson

good posts, Zendo, EatMo...

Until I bought this book I never understood exactly why and figured it was worth sharing the excerpts.

Seems like a good place to post this again:

Plant Development and Harvest Yields of Greenhouse Tomatoes in Six Organic Growing Systems
Janet F.M. Rippy1, Mary M. Peet1, Frank J. Louws3, Paul V. Nelson1, David B. Orr1, and Kenneth A. Sorensen2
North Carolina State University, Raleigh, NC 27695

http://www.ces.ncsu.edu/depts/hort/greenhouse_veg/pdf/HortSciencePeetOrg.pdf

OG = organic
CV = conventional

From these results, it seems possible that substrate pH management is more critical for CV than OG systems. OG substrate pH was very high in S99 when the greatest harvest yields were produced. It was also high in F98 when low yields resulted. Interestingly, in F99, OG substrate was within the recommended range, but this season also resulted in low yields. CV harvest yields responded to substrate pH in accordance with generally understood pH management principles. When CV substrate pH levels were outside the range for optimum plant development (high in F98, low in F99), CV yields were correspondingly low. Likewise, CV yields were the highest when pH was within the optimal range (S99), Conversely, in this growing season, when OG pH was the highest, three of the four OG treatments produced greater harvest yields than CV, which were the same as those for the fourth OG treatment.​
 
NUG-JUG

NUG-JUG

Member
I love that book since it's written so you don't have to be a biology\chemistry whiz to get whats going on.
 
C

compost

Active member
I run 2 27 gallon containers each with about 1 cup of lime plus what the pro soil mix had in it. Checked my run off ph for the first time day 34 of flowering and it was 6.5 . I run mainly organic and use RO water so I quess I don't have to worry. I don't ph adjust any water since it has barely anything in it to effect PH.
 
Lisdexik

Lisdexik

Member
It seems that when folks start to talk about PH in organic soil they tend to forget diversity.

Diversity is the key to success among all organic life. When diversity is high, PH is not a problem.

Increase diversity and increase water quality with natural, living water, and PH problems are minimal.
 
J

JackTheGrower

Oh yeah.. When applying say fresh ground coffee ( not grounds ) and other things I will apply in the mix some crushed oyster shell.

A sort of food that raises pH..

It's always good to think like that. But I never measure pH in that living soil and decide what I need.

Now I can see the case where some soils are biased one way or the other and so applying a lot of crushed oyster shell.

But it is the healthy soil that processes natural organic materials other than the materials strongly chemical in nature such as Lime or Sulphur I feel the life actually manages pH.

But yes is it possible to apply some things and mess up the plants ability to uptake nutrients or shock a plant not used to those materials in the soil.

I had a new clone that I fed a witches Brew I fed all the other plants with and this one clone didn't like it and promptly curled up and died.

It happens..

But generally we apply materials ahead of plant needs and let microorganisms process them into the soil food web system.

So in that pH shouldn't change too fast or too much if we apply materials that are reasonable.
 
J

JackTheGrower

what is the wisdom? Favor bacteria for Veg and Fungi for flowering?

There is always layers of things decomposing in my soil box and lately a lot of cannabis mulch.

I see great nitrogen cycling from the decaying green yet cannabis is woods and fungus works more on it than bacteria I understand.

But I'm a simple gardener so I have a lot to learn.
 
You must log in or register to reply here.

Latest posts

Latest posts

Top