Ag 101 Week 39


Why is pH so important?

The following is a conversation that started from a post I published called Amending Vs. Fertilizing from Week 5 on an agricultural social network called Agfuse. To see the post in its entirety, go to and sign up for a free account.

Pat Rogers, the founder of Agfuse responded with-

“I am continually baffled by long time farmers in my area who still don't see the value in getting your pH right. To me, it's the foundation of farming. An optimal pH leads to more efficient nutrient use which in turn helps us grow better crops (on less fertilizer no less). A good fertility plan that isn't used in combination with a good ph/amendment plan is pretty useless if you ask me.”

I replied-

“If you think of the soil as a digester similar to a gut, managing pH to be slightly acidic keeps it operating effectively to assimilate nutrients that are already present or being added in the form of manures and fertilizers. I often explain it as if you are taking advantage of what is inherently present and using what might be added as efficiently as possible. A healthy gut or soil, one being slightly acidic where as good bacteria and fungi flourish does that. pH is the linchpin to creating that environment conducive for healthy flora to thrive. 
Often, I think we don't understand all the ways pH is useful or even what drives it. It can also be a hard concept to grasp. I liken it to an abacus. You're using calcium, magnesium, sodium, and potassium, etc. balancing pH -hydrogen, to encourage a healthy system. And as you mentioned, grow a better crop with less or no fertilizer.”

It influences what nutrients will be available to the plant by having an effect on the mineralization of rock minerals and encouraging balanced soil biology for more efficient use of those minerals. 6.0-6.5 is the ideal range for most crops. However, a pH range of 6.8-7.2 can be tolerated by some as well.

The following is a chart showing at what pH nutrients are available

Google Image

Google Image

An obvious example and one I deal with on a regular basis are blueberries.

They are a great example of two things

1.     Pre-planning based on soil type and chemical characteristics is imperative

2.     pH is the linchpin of any long-term fertility plan

I think I said it best in an email to a client when giving iron sulfate recommendations for an established blueberry patch having some issues

“Iron can be indicative of the type of soil you have. Some soils are naturally higher or lower in iron or have varying amount due to previous uses. The challenge with blueberries is they can't use the iron that is present because it is bound in the soil due to the pH being so high. You have to give it to them in a form that is readily available until you adjust the pre-existing pH. Then you should be able to stop amending with the iron sulfate, and they will be content with what is available to them. This is why pre-planning is probably the most critical when it comes to blueberries.” 

I’m going to go one step further and clarify that pH is something that needs to be consistently monitored because the soil always wants to go back to its inherent traits. For example, I want blond hair, but I’m a brunette. If I want to keep my hair blonde, every four to six weeks I have to dye the part that has grown out, because inherently it grew out brunette. Just as you want to grow blueberries, every 1-3 years you need to have a soil test done and need to be using the necessary amendments to ensure the pH will be within a range conducive for growing them.

To adjust pH, some common amendments are

High calcium lime

Dolomitic lime (high magnesium lime)


Elemental sulfur

Fall is a great time to soil test. It is also a great time to amend soil to have the time necessary to prepare for the next crop.

 For a free printable pre-planting application chart for adjusting pH

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