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Discussion Starter · #1 ·
I have sifted out a lot of debris and gravel from the soil, respectively I am still in the process. Now missing about 3" of height, which I want to replace with a suitable substrate.

The soil is very sandy, contains 2% humus, has a pH of 7.3, contains extremely high levels of zinc at 23.4 ppm (target: 3 ppm) and high levels of copper (3,6 ppm). So far I was only looking at the too high pH, low levels of boron and manganese, and had overlooked the problem with zinc, as it was also high in an older analysis, but not as extreme. Here is the analysis from mid September 2022 (was lying fallow for 1 year, values in ppm):
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The sample came from an excavation 2 to 18" below the surface into which I want to mix the additional substrate.

Zinc was already somewhat elevated in a sample of the top soil layer at another site from February 2022, but further down the level appears to be 3x higher:
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However, the sample was from a relatively small area I had just excavated and of course could be a local problem. But I have diseases in the lawn in the other areas every year and also have the impression that the lawn (TTTF/KBG) has relatively weak roots and thus dries out quickly.

Adding peat would lower the pH and increase the humus content, but also increase the soluble zinc content even more.

Is it known what effects too much zinc (and copper) has on TTTF/KBG lawns?
 

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St Augustine and Centipede 2 acres
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I think you are asking this — I excavated an area and I still need to add 3 inches of soil to come to the desired height. I took a soil sample and here are the results.

Don’t worry about everything right now. Start with the high Ph. Peat moss will lower the Ph so adding peat and tilling it in with the existing soil will get you a lower Ph. After bringing it up to height, take 10 samples of the area at a depth of 3 to 4 inches. Combine these samples and take some of that and get it tested. It should now be on the acidic side. Now is the time to easily fix if not. If you need lower, add some sulfur and more peat.

Use ammonium sulfate fertilizer for nitrogen since it is 21-0-0-24. This means that every 4 pounds of AS contains a pound of sulfur. Overtime your Ph will continue to drop. You can add micro-nutrients as the soil samples indicate. Lowering elemental metals like zinc or copper can only be solved by dilution (replacing existing soil).

My personal belief is that chasing perfection will cost a lot of money and a lot of effort, all leading to a lot of disappointment and alcohol consumption.
 

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Discussion Starter · #3 ·
I called the lab that did the soil analysis. They told me that a concentration of 30 ppm zinc would still be acceptable. At least one would have seen a well growing lawn on a soil with this zinc content.

The value of copper in the soil here would also not yet be toxic. This would be expected above a value of 30 ppm.

Rather, by reducing the pH with peat, the amount of available manganese is significantly increased. Reducing the pH by one unit increases the concentration of soluble manganese by a factor of 100, which in their view is much more important than the disadvantage of also increasing the amount of zinc. Along the way, it also increases the storage capacity of water and nutrients. Then I guess I will stick with the plan.

Actually, I wanted to have a mixture of bark humus and peat delivered, but the supplier had increased the prices by 50% and peat is still cheaper to have elsewhere. But I will ask again, because the at least the fertilizer prices are falling here already again and bark humus would please me a little better, because the density is higher and thus probably also the mixture less sinks together.
Use ammonium sulfate fertilizer for nitrogen since it is 21-0-0-24.
With it I had fertilized the last 2 years about intermittently. The rest of the time I used usual NPK fertilizer. The pH value has obviously not changed. I had also tried elemental sulfur without any noticeable change. But peat immediately lowered the pH from 7.2 to 5.3 in a tiny test region of 3 sqft (Mix soil with peat moss to lower the pH?). I would like to mix additional potash magnesia and horn meal into the soil, because both K and Mg are low and N anyway.
My personal belief is that chasing perfection will cost a lot of money and a lot of effort, all leading to a lot of disappointment and alcohol consumption.
I hope you only believe it and did not have to experience it yourself.;)
 
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