Growth rate, or radial- or basal increment, is a function of an assortment of interacting variables: species and existing stand conditions (genetics, stand density and competition, stocking levels, canopy position, live-crown ratio, etc.); topography and soils (hillslope position, site index, soil moisture and drainage, pH, fertility, compaction, etc.); weather (strong winds, ice damage to crowns, excessive heat, precipitation patterns, drought, flooding, etc.); insects and disease; past high-grade logging removing the most vigorous species in the stand; grass and broadleaf control; etc.
Diameter Growth and Survival of Illinois Species: http://www.nrs.fs.fed.us/pubs/rp/rp_nc257.pdf
Every CRP tree planting in Illinois must meet minimum survival requirements -- generally, this minimum threshold is 300 trees per acre. IDNR district foresters and NRCS/SWCD field staff monitor CRP tree plantings for compliance.
If you're interested, we will be holding our 2nd East-Central Illinois CRP Reforestation Tour on October 26, 2016. Please contact Mr. Jonathan Manuel with the Champaign County SWCD office (Jonathon.Manuel@il.nacdnet.net) for sign-up information.