"Night Soil" is human excreta, not cattle: [en.wikipedia.org]

Yes, it has been used on fields in the past. It's really the worst thing for the job - contains far more bad and virii than anything out of a cow, steer, or pretty much any form of livestock (including flying dinosaurs aka birds). Truly hazmat.

Until the late 1960s, playing fields at city parks in San Francisco were fertilized using dried sludge from the sewage treatment plants. Worked fairly well as a fertilizer, but they later found that it was full of heavy metals from the (at the time common) industrial plants in town, as well as being insufficiently heated to kill the bugs. And all of us kids played in it. Uh huh. Amazing we didn't have all those oddball illnesses before vaccines, right? And I'm sure SF wasn't alone in the practice.

Were there sludge trains? I think SF's all got hauled off in trucks, but at least 2 of the old sewer plants (North Point and Southeast) had rail service or could have had it (tracks in the street, anyway).