Lawn Soil Tests Are In - July 2019


Back in June, I posted a photo of a couple of soil tests from Soil Savvy that I had purchased to try to ascertain the exact details of our soil in the lawn.  I thought it would be a good chance to get a baseline and to understand if we had differences in the soil that was left undisturbed in the far back of our lot and the more clay-like soil that is lying underneath the sod closer to our house.

I did exactly as the instructions said to do:  pulled up small samples from various parts of the lawn and mixed them together.  For each of the two samples.  Mailed them away and then waited a little bit.  A few days later,  received a couple of emails with links to the results. 

At the top of this post, you'll see the results from what I call the "far backyard".  This is soil that is totally undisturbed and grass that we inherited.  Based on my experience, it is softer, not as hard to pull a plug out of and A LOT less clay when I turn a shovel over.

Below, you'll see a combined result for the areas that we sodded after we built our house.  All of these areas were filled in, leveled and then the sod was added on top.  All of these areas have a thin layer of topsoil and then A LOT of clay. 

In doing the soil test, I was (of course) looking for the N-P-K situation with both lawns, but I was also looking at a few other things:

1.  pH.  I posted all about how I had a REALLY bad wild onion situation in our backyard lawn this year.  Mostly in the 'far backyard' undisturbed soil.  Admittedly, it was probably like this in year's past, but I never really paid much attention.  I posted about how I removed quite a few clumps this year.  The other remedy is adding lime to increase the alkalinity of the soil to make it a little less hospitable. 

2.  Clay soil vs. non-clay soil differences.  I was figuring that the clay soil test was going to come back with different results due to clay soil not having much organic material and - from what I read - potentially having higher nutrient content. 

So, what did we find out?

First, let's look at the far backyard (the top one). 
  • All three of the N-P-K are below the target area per Soil Savvy.  Nitrogen is the *closest* to the target level.   Phosphorus is the furthest away from the target.  My most-recent application was Milorganite (5-4-0) and Humic Acid.  
  • Calcium, sulfur, sodium, zinc, copper and aluminum are all fine.  
  • I don't think I really care about boron.  Do I?
  • Iron is on the high end of the spectrum.  But, still in the target range. 
  • Magnesium and Manganese are both high. 
  • pH is 6.26 and currently falls in the target range.  But, I think I can push it more.
Key takeaways for the far backyard - the undisturbed soil:  I can put down quite a bit more fertilizer and be just fine.  I need to think about using a balanced fertilizer or somehow consider a way to augment the Milorganite with some potassium since it includes none.  I also notice that the pH is a little low and if I want to get rid of the onions, I'm thinking I can put down quite a bit of lime to increase the pH a little bit and make the far backyard a bit less hospitable to the wild onions.  

Now, let's look at the clay soil that is beneath our sod:

  • Nitrogen and Phosphorus are low but potassium is close to the target range.  Nitrogen is lower in the sodded areas than the far back.
  •  Calcium is high.  Way higher than the far back.  
  • Magnesium is double what is in the target range. 
  • Iron and Manganese are both higher in sodded areas, but Zinc is lower.  
  • pH for the sodded area is on the high end of target, but is higher than the far back.
The tests have been a lot of fun and have provided some interesting data.  Of course, the tests could be outliers, right?  Like, the soil samples I sent in were heavy in one thing or the other because of where I pulled them from?  Totally could be.  

But, I think I'll try to do one of these tests next Spring/Summer and based on the treatments I'm going to put down (ahem...lime is coming, backyard), I am going to *into* the tests hoping/thinking that I can/should have moved some of the numbers in specific ways.  I also will (for the first time) attempt to put down some Fall lawn food - which should increase those N-P-K numbers, right?  Or if it is Milorganite, at least the N and P?!?

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