Selenium helps block the formation of free radicals. Can be found in egg yolk, seafood, poultry, kidney, liver, muscle meats, whole grains and seeds but the soil needs to have selenium for these to uptake... So I read....
No, but you can add selenium through tree spikes that slow release the selenium to the trees who then deposit it in the soils through their leaf shedding and wood decay when they fall down go boom. Additionally you can add it through something like kelp or other supplements. However, you'll need to keep adding it as the selenium washes out. Our farm is fortunate to have good selenium in our soils as we're up in the mountains where it comes from. Farms down in the river valley have less as they've had it washed out and in some places they have next to none. Selenium deficiency can cause serious problems with animal growth. See:
First, Minnesota is interesting as parts of the state seem to have good seleniumlevels while other areas are low..It's right on the line. Here is a US gov. interactive map, you could check your county and see what local soil levels are.
If you have livestock and are feeding them a mineral supplement, then the composted manure can be a source for micronutrients for gradual soil building. (Or maybe you know someone who has..) Organic sources are absorbed best by animals.
Interestingly, with livestock there can be problems from selenium deficiency in some regions and at the same time high-selenium toxicity issues in other areas.
People are increasingly finding they have low selenium levels as industrial agriculture gets bigger and more concentrated...lots of feedlot animals are fed up on grains that are grown on selenium deficient soils. If you eat meat, you might want to just source out a local farmer who pays attention to herd nutrition...maybe you can score some naturally raised grass-fed beef