In his Times Weather Eye column of 30 June Paul Simons offered an explanation for the distinctive smell of soil after rain.
Streptomyces bacteria spores in the soil ‘pop off’ when the air turns humid & get kicked up in clouds when rain hits the ground. If you are lucky enough to have a very keen nose for this smell you can even use the humid phase to forecast the approaching shower.
I guess ploughing just kicks up even bigger clouds of spores & that is what explains the especial intensity of a freshly turned field in autumn. It is not clear however if it will be a good or a bad thing to have fewer spores released if farmers follow the latest green advice to stop ploughing
Picture Credit: No. 14 from Soil Microbiology and Biochemistry Slide Set. 1976. J.P. Martin, et al., eds. SSSA, Madison, WI
