[pseudohadamard]

Someone strolled around and dropped a squirt of glyphosate every few paces. That stuff has an area effect so it'll kill grass in a small radius, if they'd done the (apparently) obvious and sprayed a continuous stream to mark out the digits it'd have ended up as a big blobby mess. Whoever did this put some thought and planning into it.

[gus_massa]

I was thinking about table salt.

But it's strange that all the dots appear to be the same size, so I'm guessing round object. Is it possible to go there with a round pick nick blanket and sit every day in the same spot until the grass die?

[pseudohadamard]

No, it's much easier to do than that. If you've seen the Great Escape think something like that, run a tube down the inside of your trousers, tank of glyphosate in some innocuous bag, and a valve that dispenses a fixed amount each time it's activated. To anyone watching you're wandering somewhat randomly around the lawn taking selfies or texting or something, when in fact you're poisoning the grass every three paces.

[gus_massa]

In that case I expect lines of very irregular blobs of different sizes. The number 8 has like 40 almost equal circles that have the size of the car. They are very circular, all have the same size, the same internal structure.