I want to restore land infested with Russian thistle (Salsola tragus L., Synonyms Salsola iberica Sennen & Pau or  Salsola kali L.).  The land is located in southern Utah about 5 miles north of Arizona (Kanab, Utah).  I am going to drill in a mix of grass seed and forb seed obtained from Granite Seed Company.  The soil is a red, heavy silt (probably contains a fair amount of clay) that is derived from Moenkopi mudstone.  Before reseeding I plan to mow the Russian thistle and collect the clippings plus seed and destroy them. 

The question that I want answered is: Is there a very short half life herbicide that can be used to eradicate emerging Russian thistle seedlings before I drill in the seed mix that will be used for  re-vegetation that will not kill the seedlings of re-vegetation mix.