It took 41 nozzles to cover the entire boom on 30" spacing. There was one nozzle on the far end of each boom and there was a nozzle in the exact center of the boom.

If your tire spacing is 120" and you're trying to run between the rows on row crops and you want to use drop nozzles to protect the whorl on corn you pretty much have to have a nozzle right in the center of the boom.