another article - soil pH

[Paul Wheaton]

Folks have asked me to let them know here when I write a new article ...

This one is on soil pH.

just an fyi ....

[Ken Scharabok]

I just scan read the article. I suggest contacting your local library to see if they can obtain a copy of More Food From Soil Science: The Natural Chemistry of Lime in Agriculture by Dr. V. A. Tiedjens. He also wrote Olean Farm, U.S.A.: An Agricultural Success Story, which is on basically the same subject. (If your local library can't obtain the first book I have a couple of copies available on eBay.)

Essentially the crux of his presentation is that soil pH is simply a very poor indicator of the need of soil for at least calcium. Rather you have to do a trace mineral analysis to get base saturation of calcium, which should be at least 80%. He cites some fields on which he applied massive amounts of crushed limestone and pH actually decreased.

You can increased base saturation of calcium without affecting pH at all by applying gypsum.

Not all limestone is the same.

Soil analysis will vary by season. For example if you took four samples, spring, summer, fall and winter, from the exact same spot likely each analysis would be different.

On soil testing, if you have the money to do so send the exact same soil samples to four different labs. You are likely to get back four different analysis, with some readings varying significantly.

I suspect if you put a teaspoon full of straight ag lime in with the samples they would still tell you you needed to spread 1-2 tons per acre. One of the former County Ag Agents once told me he had never seen a soil analysis come back from the state lab which didn't call for 1-2 tons per acre. He suspected they didn't really even test for it.

As you can tell I am not much of a fan of relying heavily on soil analysis tests.

[Paul Wheaton]

Would you say "pH is a very poor indicator" or ... maybe ... that a farmer would be much wiser to have a better overall understanding to soil chemistry than just pH?

In this article, I do mention that this is something of a quickie summary that is better covered in a bunch of a books.

In the last couple of years I've been thinking about audience a lot. Who is the article for? Who do I want to write for?

Lots of times, I'm just itching for ALL of the information. And I'm trying to learn about some weird little quirk of something. Buried in the details. Other times, I'm trying to answer somebody's quick question. They don't want all the details. They want something they can write on a post it note and take home.

So I think there is a spectrum of knowledge and desire for knowledge.

0 - don't know, don't care
1
2
3 - reading books
4
5
6 - writing books
7
8 - years of first hand, full time research on this small topic
9
10 - lifetime of detailed knowledge on this small, focused topic

I think when I'm trying to learn a lot of this stuff, my interest is around "5".

But I'm trying to write for the 0 to 2 folks. I don't feel qualified for anything else.

..... I guess what I'm trying to say is that I agree with you. And maybe I should amend my article a bit. I think there are a lot of people that are told about pH and they aren't sure what to do about it. And they know people that just throw down lime every year and have great results. Why? So I think that this page keeps people from doing what their friends do without at least first checking to see what their pH is. And I think that the stuff about nutrient availability introduces some of the ideas of micronutrients - something that they might choose to learn more about in their soil test.

Let's face it Ken, I think this topic is about a thousand times richer than your knowledge and my knowledge combined. Some folks are willing to put in 20 minutes to learn a bit. So I'm trying to write enough to make the best of that 20 minutes. I'm willing to add to the article, or change it. The trick is that the absolute truth would fill a library. So, when trying to keep it short and sweet - but at the same time not be confusing .... well ...

Some important things I think I conveyed:

1) get a professional test. Cheap gizmos are garbage.

2) go easy on the amendments.

3) Hey look! Micronutrients!

4) It doesn't have to be perfect, pretty close is good enough.

5) This stuff is safe, organic, cheap and easy.

6) How to.

7) Lots of different folks have lots of different ideas of what makes for good pH for different things.

I think this is a good intro to soil tests and using lime/sulfur. An easy first step.

.... now! On to a slightly similar topic!

I've always thought that testing soil during a wet season would give a lower reading. What has been your experience along these lines?

[Ken Scharabok]

I've always thought that testing soil during a wet season would give a lower reading. What has been your experience along these lines?[/QUOTE]

All I am fertilizing now are either pasture or hay fields. I haven't done a soil test in probably eight years. Normally I alternate years between spreading lime and spreading fertilizer (with seed mixed in with it).

[Paul Wheaton]

So you broadcast seed onto pasture/hay ground? Which seed? How well does it take?

[Ken Scharabok]

I have adequate fescue so usually have them add some timothy and orchardgrass, and clover on the hay fields. Last time I just had them include Johnsongrass. They don't sell it, but I simply bought out of state and had it delivered there. JG makes an excellent hay if it is thick and is cut when not much more than knee high.

Coop already charges for fertilizer spreading so doesn't add an extra spreading charge for putting in seed.

On how well it takes - really depends on weather for next couple of weeks after spreading. I figure when seed is put down with fertilizer, and it rains nicely for the next two weeks or so, some of the seed will establish itself.


I also have them include boron and sulfur to the fertilizer (N-P-K).

Spreading salt is also said to be popular in New Zealand.

[Cabin Fever]

I think your article will, at a minimum, get people to think about pH. Most people focus on fertilizers and do not understand how soil pH can influence the availability of nutrients. Ken is correct in stating that soil pH should not be used as an index of soil fertility. For instance, a soil may have sufficient to excessive levels of iron, but at high pH the iron is immobile (“tied-up”) and the plant may be starving for this nutrient.

I would recommend that your article describe exactly what form of lime it is discussing. You use the generic term “lime.” Lime can be “quick lime,” “hydrated lime,” or “ag lime.” I assume your article is referring to ag lime....which can be crushed, pulverized or granulated (pelled) calcitic lime or dolomitic lime.

Secondly I would recommend a bit more discussion in taking a good sample for analysis. The article talks about mixing sub-samples from three locations into one composite sample for analysis....and then doing it over from different sites in the yard (ie, west yard, south garden, etc.) It would be better be take samples from more locations....maybe 10 or 12....and mix for each “site” sample.

Adding too much ag lime will not make the soil “toxic” as the article implies. The pH of 100% ag lime is only 8, consequently it will not increase the soil pH above 8 no matter how much ag lime is applied.

I realize that the article is written for the average homeowner, so simplicity of the application rate table is adequate. However, just so you know, the amount of ag lime to apply to a given soil is more related to the soils buffering capacity than to it’s actual pH value. In other words, two soils can have identical pH, one soil has a low buffering capacity and the other a high buffering capacity. The soil with the high buffering capacity would require more ag lime to raise the soil pH than the one with low buffering capacity. You touched on this concept when you contrasted a sandy soil to a clayey one. But buffering capacity is determine by other properties in addition to texture.

You might want to consider adding a bit more explanation to the Colorado State University table. I use this exact table in some of the teaching that I have done.