House Ag has the text of the agricultural amendments to the carbon bill. (There's also a summary.) I was wrong in my assumptions on how it might work--I was figuring a direct NRCS to farmer linkage. Not so, instead there's provision for "offset project developers" and "independent offset verifiers" which sound like private entities. So the NRCS would be working through these third parties. (This is based on a fast skim and I don't claim any expertise in the area.)
Seems to me this is partially political. (I know you're surprised.) By using third parties you increase the chance of getting influential supporters and contributors on board. Use a government agency, you only get the agency's employees. [Updated: Did I ever link to the National Farmer's Union testimony? They're currently acting, I think, as an offset project developer. They've got an interesting website application show in the testimony as well.]
Because I'm on the weak government kick recently, I'll go on to say this is an example of how and why we end up with weak government (otherwise known as protecting our liberties); the process of getting legislation enacted requires logrolling and obeisance to local power centers.