some one got to it before me but bro i wouldnt nuke the soil if i were you because that shit will get contaminated by all sorts of other rapid growing bacteria possibly even mold if it has the right humidity and spores hop on it (which are electrostatically charged and stick to everything). id send an email to the soil producers, they might be there for a reason or its a bad batch and theyve made you an unhappy frog lol but that really blows, you might be able to kill them with hydrogen peroxide, which shouldnt affect all the bacteria, and after a few days the H2O2 will have decomposed and evaporated away (obviously test it out on a handful of soil before you pour a liter into your pot to make sure what ever it is they are dies). good hiroshima on the nematode vibes your way!!!