How to reset a form element to its ordinary default value?
field_get_default_value - Helper function to get the default value for a field on an entity.
Usage:

&lt;?php
  $field = field_info_field('YOURFIELDNAME');
  $instance = field_info_instance('node', 'YOURFIELDNAME', 'YOURNODETYPE');
  $defvalue = field_get_default_value('node', $node, $field, $instance, $node-&gt;language);
  print_r($defvalue); // Here structure, like $defvalue[0]['value']
?&gt;