Soil testing

[MontyJ]

Monty, what is OM anc CEC?

I did use lime a couple of years ago, but hardly any at all so I don't think it made a huge difference.

OM = Organic Matter
CEC = Cation Exchange Capacity.

The CEC is used in conjunction with the saturation levels to determine the balance of the soil. You could have a Ca of 22,000ppm, Mg of 2000ppm and K of 2000ppm and guess what? If the CEC is 15 NONE OF THOSE LEVELS ARE TOXIC! The CEC measures the capacity of the soil to hold nutrients in a form available to plants. Just because a particular nutrient is high doesn't mean it's bad. If you only look at the "Low" High" "Very high", you are missing the big picture. Obviously that's an exaggeration, and there are some nutrients that are toxic at low levels such as boron, but Boron isn't a cation is it.

If you want to scoff at soil samples, fine. Perhaps others would like to learn about them. I think the "If it ain't broke, don't fix it" horse has been beaten enough. Soil samples can do a lot more than just fix things, if you understand them. They can also head off a problem before it becomes a problem. Also, the size of the area in question has absolutely no bearing at all. It doesn't matter. Area size would only be required if corrections were needed which in this case they are not.

 

[seedcorn]

Monty, not to get into argument, but the area being represented is critical. I don't care what your CEC's are, there are huge environmental problems with the numbers you suggest are fine!

If your garden is doing well, you are adding compost, what value is a soil test telling you that your levels are good? Without knowing sampling methods, area tested vs area represented, previous sampling history, varieties to be grown, area tendencies, a soil test is of limited value--notice limited, not worthless.

If someone wants to do soil samples, no harm but you can't fix what isn't broken. You will just break what is good. I get the impression that some of you think the pH needs to be fixed. Why? In Indiana, that pH would be hard to maintain--our soils tend to maintain a pH of 6.7. In some western states, they would consider to get their pH that low a victory.

Bottom line for me, if your garden is great, keep on doing what you are doing. Keep the course until you start to see a problem, then head it off, starting with examine what changes have happened and, yes, a soil sample.

 

[897tgigvib]

Monty, how would a person get a better cec number?

 

[MontyJ]

I got up a little early this morning before work so I could run the numbers of the soil test. Since I don't have the buffer pH I had to use an estimating factor to determine the CEC. My calculation may be slightly lower than the actual CEC, but not enough to make a difference. This is for illustration purposes only, but should be pretty close.

CEC = 11.6
Base Saturation = 94.83%

Nutrient Saturation:

K = 1.91%
Ca = 79.88%
Mg = 13.05%
H+ = 5.17

As you can see, the nutrients in the soil are being held by adsorption in the soil. There is nothing to run off. The numbers listed as very high are listed that way because they are out of balance and are causing the high pH. If you want to see the math, I will be happy to show my work.

 

[MontyJ]

Monty, not to get into argument, but the area being represented is critical. I don't care what your CEC's are, there are huge environmental problems with the numbers you suggest are fine!

If your garden is doing well, you are adding compost, what value is a soil test telling you that your levels are good? Without knowing sampling methods, area tested vs area represented, previous sampling history, varieties to be grown, area tendencies, a soil test is of limited value--notice limited, not worthless.

If someone wants to do soil samples, no harm but you can't fix what isn't broken. You will just break what is good. I get the impression that some of you think the pH needs to be fixed. Why? In Indiana, that pH would be hard to maintain--our soils tend to maintain a pH of 6.7. In some western states, they would consider to get their pH that low a victory.

Bottom line for me, if your garden is great, keep on doing what you are doing. Keep the course until you start to see a problem, then head it off, starting with examine what changes have happened and, yes, a soil sample.

Again, when looking at the numbers alone, area size has NO BEARING. The numbers will not change regardless of the area size. If the area was 10' x 10' or 1000' x 1000' the numbers would be the same. Which numbers are you refering to? My completely outrageous example numbers?? In that example those levels would not be toxic to plants because there aren't enough CEC sites to make them available to plants. It would be an environmental disaster though because most of that would be available for run-off. If you are refering to the numbers from the soil test, see my post above. The soil is capable of holding everything in place. Science, chemestry and math don't lie.

Also, if you look at the numbers you can see that all is not well. The Ca:Mg ratio is off. Now, I'm not one of those Albrecht ratio zealots but this test is clearly showing that there may be a drift towards a calcitic soil. Future tests will show whether that is the case or not. Still, it's not in trouble yet, and everything is in adequate supply for good plant uptake and growth. If you wait until a problem shows up in your garden to take a soil test, you could lose an entire season. By monitoring what is going on in the soil, you can head off a problem before it starts.

 

[MontyJ]

Monty, how would a person get a better cec number?

CEC can raised by adding humus to the soil. That's one reason why compost is so good for the soil. I have to go to work right now, but when I get home I can explain CEC if anyone cares.

 

[897tgigvib]

Yes! Please when you get a chance, explain CEC and the whole thing. Sounds like cec fixes and moderates a lot, and is easy to increase, and is a very important number.

 

[OldGuy43]

While we're on the subject how do we feel about the DIY kits that you can buy most everywhere?

 

[bobm]

MontyJ... when you say area size makes NO BEARING ... take my 20 acre property in Cal. for example. It is at 503' +/- elevation of rolling high desert with clay soils deposited by errosion from the high Sierra Nevada Mts. ( mountains rise 500'-1000' within 1/2 mile to 3000 ' within 3 miles )over eons of time. There is meandering black, white, red, and yellow soils changing at about every 10+/- feet deposited by creeklets and flood waters. Some areas of my pasture even has white salt deposits on the soil surface where no grass grows. So how can I get an accurate soil test ? :tools

 

[897tgigvib]

That does make a lot of sense BobM.

My guess would be each area would need a separate test, but just might be something that evens things out. Monty will probably know. He may have been talking about most places that have large expanses of similar soils, I don't know.

This is a great thread!