How long can you get away with leaving it in one place before the grass burns?Move your tractor daily as the ammonia smell builds up very fast and will burn grass.
I'm doing the tractor method with 6 quails but my problem is my backyard is very small and exposed. Only a few areas get shaded and the sun is really strong so I'm basically limited to the edges otherwise they will get a full day of 45oC sun.
I definitely know what you mean about the ammonia smell though, it's irritating to the nose if I get too close.
My tractor has an inside part with a roof that has mesh on the bottom, I use deep litter in there to deal with some of waste. The outside part which is larger has no mesh on the bottom.