Well, they always talk about Strontium 90. Isn’t this a direct reaction product? Neutron irraditation of ground material is an interesting point, and one I’m not familiar with, so I’ll grant what you say. I guess this would be mostly due to metals in the soil ?
With that many neutrons available you’d get quite a stew from soil or concrete. There are n-gamma activation reactions for N, C, O, Si, Al, Fe, K, Ca.....
The fallout from an air shot will have bomb debris, what’s left of the Pu or U, the U casing, and any structural stuff, probably Fe, Al, B, others, plus all the isotopes you get by neutron irradiation of these materials, and fission products of the pit. Consider that the casing absorbs a big fraction of the neutrons, so it will be very activated. Most of the activated material will have a short half life, which is part of the glow of the debris cloud, stuff with a half life less than a second wildly decaying.
The fission components are as you say Sr, and there would be Ba isotopes, Kr, Cs, I, Zr75. These all have relatively long half-lives.