It was a water spray (Bil said "aerators" around 0:44; he probably did not mean the spiky lawn care thing, but rather a sprinkle system), to keep the existing c

It was a water spray (Bil said "aerators" around 0:44; he probably did not mean the spiky lawn care thing, but rather a sprinkle system), to keep the existing chemicals on the ground from turning into dust and flying further away. (At least that is my understanding.)