How to merge two different vocabulary in one auto-complete text-field? I have two taxonomies like below:

Content--- editor pick
       --- recommended
       --- today high
Sources--- sky
       --- earth
       --- water


to attach these with blog-post i need to make 2 different auto-complete text-box.
I want to make a single text box and both the taxonomy should be suggested in that.
You can do it using Entity Reference module. You can able to reference multiple vocabulary terms using this module.

See the screenshot of field settings of field type "Entity Reference" and Widget types "Auto-complete (Tags Style)"