pH part II

In the first part of this article, I presented what the conventional approach to pH is, what it’s accused of doing, some ideas on how pH actually works in the soil and should have impressed upon you the notion that pH is hardly what it’s made out to be. There’s a claim that “good plant growth” can’t be assured unless you fix your pH, but I counter that notion and state that this assurance can only come from appropriate soil mineral nutrition.

pH is not a cause… it is an effect.

It is the reflection of the the soil makeup. In our case we want nutrient rich crops growing in fertile soil with the most happy pH of 6.4. This would afford maximum nutrient availability to the plants. If however your pH is too high or too low, the pH is not the cause of poor plant health rather it is sign, a message to you about the state of your soil mineral balance and biological activity. It’s also not the end of your gardening career if you can’t achieve the perfect reading, many native soils can be difficult to impossible to move very far. If you can’t get your pH into the ideal range experiments have shown that if a plant’s roots have access to adequate nutrients and there is no toxicity then pH makes little difference. Therein lies the crux of the problem, availability of nutrients is the limiting factor, not pH. A strongly acid or alkaline soil may be a sign that soil nutrition is in bad shape, but that can be mitigated by excellent biology.

vinesCalcium lime is not the only material that can raise the pH either, so can magnesium, sodium, carbon and potassium. Likewise sulfur is not the only mineral that will lower the pH, so will phosphorous and chlorine. On your typical farm, the heavy use of salt fertilizers creates a situation of rising pH levels, where calcium is not then being applied, resulting in a calcium deficient soil, followed by cascading nutrient failures and greater and greater problems. In your garden things could be different, or very similar, with over application of dolomite lime creating a magnesium problem, or an over application of compost/manure creating phosphorus or potassium imbalance achieving the same situation. Poor nutrient availability to the plant leads to poor plant health leads to disease and insect attack and a low quality nutrient poor product.

In my own garden space I had just this case. A slightly high pH with a soil mineral matrix that included naturally excessive magnesium and potassium, little calcium and several years of over zealous applications of manure and compost that intensified the imbalance. It was the perfect situation for induced plant stress, low quality vegetables and rampant weed problems… much to my dismay. Had I followed the conventional thinking, organic or not, a little bit of sulfur would have been applied along with more compost. Net result would have been an ever worsening change in the soil, including increasing soil compaction and no improvement whatsoever to produce quality.

What about the idea that certain plants prefer a soil within a particular pH range? For example blue berries are thought to prefer an acid soil of 5.5 to 6.5, alfalfa from 6.5-7.5 and corn and wheat from 6.5-7.0. Studies in plant nutrition and available calcium have shown the truth of the matter (Soil Acidity as Calcium (Fertility) Deficiency Albrecht), when there is sufficient calcium for good growth then pH as low as 4.5 can grow a great crop. And since low pH soils are usually limed with calcium it erroneously leads one to think that pH makes a difference. Even the nitrogen fixing abilities of certain soil bacteria on legumes only works effectively when there is sufficient available calcium in the soil regardless of the pH.

Interestingly there is an alternative way to understand pH that makes a lot of sense. Recall from the last article I introduced the idea of positively charged ions called cations, and negatively charged ions called anions. What’s the importance of this? It’s that pH is a measurement of electrical resistance in the soil. Thus a pH reading of 7 means that there is an equal amount of resistance between the cation and anion charges. A high pH indicates there is too much electrical resistance in the soil, causing a restriction in energy-nutrient flow to the plant, while a low pH indicates that there is too little resistance causing an overload of energy-nutrient flow. Keep this idea in mind as in the future we will discuss this in more detail and how we can use electrical conductivity to monitor and improve upon plant nutrient uptake.

So instead of working to adjust your pH, it’s more essential to manage the factors that construct the soil pH. A very fertile soil for high nutrient and energy production is a living biological system and must must be carefully balanced for the needs of the soil microorganism via an equilibrium of pH, soil minerals, energy, physical conditions and organic substances. Without this balance, the potential for plant nutrition and soil building erodes.

Remember then, that pH is a consequence of soil nutrient and biological interactions, it is not a cause of anything. pH can however be a useful gauge for you to monitor how various nutrients and other substances you apply are interacting with your soil. It is not however to be used to determine what nutrient, mineral or compound to apply to the soil. That should only be done after you have carefully reviewed all the factors that contribute to excellent soil fertility.

~Sean

6 thoughts on “pH part II

  1. You’re probably getting to this-but how does the average gardener determine and provide all the proper nutrients for the healthiest garden?

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