I would like to use Quantum instead of ArcGIS to make field map but before, I need to know if its possible to do spatial interpolation with definited points in a field (ex. pH points). Is there a manual to learn about it?
you can use the interpolation plugin: http://docs.qgis.org/html/en/docs/user_manual/plugins/plugins_interpolation.html
or you can use the sextante plugin, loads of different interpolation algoritmes: http://docs.qgis.org/html/en/docs/user_manual/sextante/index.html