The typical smell from cut grass is actually microbes. The soil is very much disturbed by the way we cut grass (not talking about reaping hay/wheat/etc here, just your typical suburbanite with a lawn mower). I can't remember what they are now for the life of me, but the microbiology professor at my college loved explaining to the younguns that the reason the local water tasted/smelled bad (compared to most places) was that the same variety of microbe responsible for the cut grass smell was present in high concentrations in the source for the city water. Once he pointed it out, you could pick out the similarity.