The Walden Effect: Farming, simple living, permaculture, and invention.

Soil pH

Sampling soilI'm not going to write about the fundamentals of pH because I figure most of you know:

To some extent, your pH is determined by the bedrock under your soil, but management will also impact soil pH.  For example, take a look at my test results:

Mule (1) Mule (2) CP3 (3) Back (4) Front (5) Mom front Mom back
pH 7.5 7.6 6 7.3 7.4 7 7.3
CEC 65.6 74.4 15.6 56 47.1 27.9 36.3

Notice that the mule garden --- just a few feet away from the chicken pasture (highlighted in yellow) has alkaline soil instead of acidic soil.  Soil in both spots was identical a few years ago, and I've never added lime or large amounts of wood ashes to my soil.  What I have done is topdress the mule garden with compost and manure in huge quantities, which seems to have sweetened the soil (despite various sources that report compost sours soil.)

Micronutrient availability vs. pHDepending on which crops you're trying to grow, the perfect pH for most garden plants ranges from 6 to 7 (although you'll want much more acidic soil for blueberries.)  pH is extremely important because it determines the availability of many nutrients, as you can see in the chart to the left.  Each type of plant has evolved to deal with specific micronutrient ranges, and a pH too high or too low can lead to deficiencies of some nutrients and toxic overabundances of others.

If you're worried about the pH of your soil, the first thing you should do is to look at your CEC.  Although a high CEC is generally a good thing, the value also means that the soil is very resistant to changes in pH.  Raising the pH of my chicken pasture soil would be relatively easy due to its low CEC, but lowering the pH of my garden soil would be much tougher because of the high cation exchange capacity in that rich soil. 

For now, I'm going to leave my soil pH alone, but I will probably opt to test the soil every year and keep an eye on this figure since a much higher pH could be problematic.  Traditionally, soil pH is raised with lime and lowered with sulfur, but due to my high CEC, I would probably opt to apply acidic organic matter instead if I wanted to lower my garden pH.  I suspect my chicken pasture will become more alkaline naturally as chicken manure and plant debris enrich the ground.

Our chicken waterer keeps the flock active, tempting them to the far end of the pasture for a sip of clean water.

This post is part of our Holistic Soil Test Analysis lunchtime series.  Read all of the entries:

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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Thanks, you guys! I am learning just a s much here as I am in my soil science management class.
Comment by Paula B. Fri Nov 11 17:52:04 2011
Thanks for saying that! I hoped the lunchtime series wasn't too hard-core. I needed to get all of the cool technical stuff out of my system so I could pare it down to the more understandable basics for the soil test section of the book. :-)
Comment by anna Sat Nov 12 11:16:15 2011

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