Cold Soil and Direct Seeding

I've happened on to a project (1994-2009) called the Alberta Reduced Tillage Inititive (ARTI).  This project had many partnerships, including private, public, and education.  They studied many aspects of Direct Seeding (DS) including effects of cold soils.  The following URL access' their site.
                          http://www.reducedtillage.ca/about.aspx
     This is a big site.  One study indicates that tall standing stubble (stripper header) warmed faster than the short stubble mat left by regular platform header,  and allowed better seed/soil contact with disc type opener.
     I will update this post as I have time to read other studies.