Jim's 2020 Soil Test

[Jim]

Good day. This is an amazing service you provide. Thank you very much for doing this. I got a really bad one for you--even I know enough to see that. This is Central Texas black clay. Growing Bermuda. Now that I've seen these results, I'm honestly surprised that my lawn is fairly decent. Let me know what you think.

[andy10917]

Moved from Soil Test Interpretation Queue by Moderator

[andy10917]

Please place a link to this posting into the Soil Test Interpretation Queue, so we don't forget your posting. I'm moving your posting out of the queue and into its own thread,

Now for the bad news: even a quick glance shows me a Calcareous Soil situation. This indicates a soil so dominated by Calcium that the results are distorted. We can guess at the amount of distortion, or you can have the soil retested by Logan. It will cost you another test cost, but the results will not involve guessing. Up to you - Logan saves samples for a couple of weeks, so retesting doesn't involve resending samples. Let us know which direction you want to go.

Too bad that you didn't read the "Posting a Soil Test for Interpretation" thread before sending - there is a warning about this situation in your area.

Note: if you are in the Dallas/Ft Worth area, the Austin, TX or the Twin Cities (MN) area, request "Ammonium Acetate extraction of cations" in your submission.

[andy10917]

Also, please edit your profile to include the "Lawn Size" and your "Experience Level" - this helps us to understand and determine the detail that is appropriate for you, and the amount of work you will need to do.

[Jim]

Yikes, not my finest hour. Sorry about that. I'll fix my profile and order the correct test from Logan.

[andy10917]

Don't worry about it.

We'll wait for the new Ammonium Acetate results, which I'm guessing will be two days after you call them (this happens a few times a year). We'll get you going!

[Jim]

Good morning. Logan says they have two ammonium acetate tests, 7.0 and 8.2. Which one do I need?

[andy10917]

Use the 8.2 test

[Jim]

Here it is.

[andy10917]

Put a link to this thread into the Soil Test Interpretation Queue

[andy10917]

I got a really bad one for you--even I know enough to see that.

OK - this is far less terrible than your initial reaction indicates. While the scenario of crazy numbers came partly from the calcareous nature of the soil, it was compounded by the fact that you identified the soil test depth as 6", and not the 4" depth that the "Posting a Soil Test for Interpretation" sticky thread at the top of the Soils Forum requests. It's a straightforward (but annoying) set of math conversions that I need to do to see the numbers that are similar to what you may have seen on other folks' reports. The 4" depth is the middle of the grass root zone, and the 6" depth is more for deeper-rooted agricultural crops. When the soil is reported at a test depth of 6", all items that are shown in lbs/acre are inflated by 33%. So, with the inflation of calcareous scenarios and the 6" vs 4" issue, you have inflation on top of inflation. I've corrected for it.

As you said, you have a soil structurally that is showing a very high TEC of around 28 - this comes from the "black clay". They typically drain slowly and are shallow soils - often right on top of limestone. This means a change in irrigation tactics is needed - the standard 1"/week practice just won't work in soils like your's. You'll have to find out be experimentation what drains OK and still saturates to the whole root zone. The OM number indicates a poor organic matter number of 2.31%. Shallow soils with low OM numbers indicate that a concentration on the addition of mulched leaves, peat moss and/or compost is in order to both raise the OM number and build up the soil. LOTS of OM...

In the cations, the Calcium number of calcareous soils is so high that it skews the "desired value" of all other cations, which are calculated as a ratio to the Magnesium and Potassium numbers. You do not have a problem with shortages of Magnesium or Potassium - the ratios of them to the Calcium is calculated against a crazy number, and reported shortages don't exist. Some folks (and even some agronomists) mistakenly "chase the ratio", which is a waste of money and can actually make the situation worse.

The Phosphorus number is good.

The Iron number is very poor, and at your pH of 7.9 wouldn't be available anyway. You could try Milorganite, which has a naturally chelated form of Iron, buy chelated Iron ($$$), or read up on foliar FAS treatments (every 3 weeks or so - lots of work). Your current Iron situation is probably affecting the lawn's color negatively.

In the micro's, Boron and Zinc could use supplementation - let me know if you wish to do that this year.

Don't even ask about lowering the pH - it's impossible in your situation. Bermuda will grow in that soil if you do what is listed above. With your adequate levels of Potassium and Phosphorus, you could get away with Urea at 2 lbs/K monthly during the growing season. Urea is cheap.

That's it - if you want to read up on your soil a bit more, click the link: Austin Area Soil Article

[Jim]

I'm really glad I had you look at this because I was already looking around for sources of Magnesium and Potassium. You have saved me a lot of money and work.

Yes, I'll go ahead and tackle the micros as well.

[andy10917]

Get Twenty Mule Team Laundry Soap (for Boron) from the grocery store, and Zinc Sulfate from Amazon/EBAY. Apply three tablespoons per 1000 sq ft of each every 60 days, as outlined in the Micronutrient Application Guide.

[Jim]

I want to attack the OM issue aggressively, and since my front yard is only 1,000 sq ft, I should be able to do some real damage. With such a small area, I may use some paid sources (bagged compost, peat moss), but I also found a source of free sawdust.

I saw in other threads that it is okay to use, but my question is how much would you consider too much and should I add extra nitrogen to compensate?

[andy10917]

Overall, the official limit is "don't cover up the crowns of the grass". That typically is 1/8" to 1/4". Lots of smaller apps are better than clobbering it all at once, and avoid the problem of it forming a "crust" at the soil surface. How do you know when to apply it again? When you don't see any at the surface. Be aware, sawdust is preferred by beneficial fungi, and not the same process as things like grass clippings, SBM, Milorganite, etc -- which typically are bacterial. It will take a bit of time to build up the fungal component in the microherd, but you should see an acceleration as they get a steady diet of sawdust for a few months.

To spend wisely and get good results on 1,000 sq ft, I'd do a mix of peat moss and sawdust -- I wish I could afford to do that regularly on 1+ acre.