I recently bought a new house in northern PA. This year when spring hit my backyard was a disaster. Most of it looked dead. None of my neighbors lawns looked like mine. As the weeks/months went on it started to look a bit better, but still a mess. Tons of weeds everywhere. Dead patches. So, I decided to take a soil sample and have it tested. enter image description here


The most obvious problem is that the nitrogen phosphorous and potassium levels are all completely off the scale.

If I had to guess a cause, somebody (not necessarily you!) applied some fertilizer and got the concentration completely wrong. The high levels have killed off the grass but the tougher weeds survived.

The other problem is that the pH is low (too acidic) but that might just be a side effect of the insane NPK levels. For example the pH of ammonium nitrate is around 5.25 and the level in your sample is maybe 20 or 50 times higher than it needs to be to grow a good lawn.

The high sulfur level will also lower the pH.

We don't know what type of grass your lawn used to be, but a reasonable target value for pH would be 6.5 to 7.

Probably the easiest way to get the NPK back into a sensible range (if it works) is deluge the lawn with water for several months and hope you wash them out of the soil. Otherwise, you will be looking at removing all the top soil (maybe to a depth of a foot or more) and replacing it, which won't be cheap.

Trying to get the grass growing before you sort the NPK levels out is most likely a waste of time - and a waste of money, if you buy seed or turf.

  • Looking at the website, those soil tests are pretty cheap, so it would be worth doing another one after say 3 months of "wash out the NPK" watering to see what the effect was. Don't worry about the NPK levels getting too low - that is cheap and easy to fix with the correct amount of fertilizer.
    – alephzero
    Jul 31 '20 at 12:08
  • The house sat empty for about 2 years. The grass was insanely overgrown when I moved in. I don’t think anyone was putting fertilizer on it. Is there anything else that could have caused these insane numbers?
    – Jen
    Jul 31 '20 at 12:11
  • I lived in a house with some numbers similar to yours (off the chart P and K, and high sulfur, but low N). The "soil" (calling it "soil" is actually an insult to soils everywhere) was truly horrible - it was so clayey that we could've opened a pottery. This was caused by the builder removing (and presumably selling) all of the wonderful topsoil that was originally there, leaving only the subsoil in place. It's conceivable that your soil was always horrible, due to the builder dumping "fill soil" or subsoil after finishing the house.
    – Jurp
    Jul 31 '20 at 13:29
  • The house was built in the early 40’s. I’m really at a loss about what to do other than saturating it with water for months like the suggestion above.
    – Jen
    Jul 31 '20 at 16:13
  • 2
    Hmmm. P won't leach out of your soil anytime soon, as it moves very slowly through the soil profile. K moves quicker, but not as fast as N. The rest of the minerals make absolutely no sense - Low Mg is much much more common than high Mg. Same with Sulfur and Manganese. Because these numbers are so off-the-charts, I recommend submitting a soil sample to a different agency. In Wisconsin, our Extension performs soil testing - is that the same in PA? If so, it would be worth the money to have a second opinion.
    – Jurp
    Jul 31 '20 at 21:50

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