[Answer]-How to set default field values when Django's reverse() is used for admin "add" page?

you could do it by passing some values in GET, but this wont work always(e.g. for datefields etc..), i would do it with custom ModelAdmins with get_form method

class MyModelAdmin(admin.ModelAdmin):
    def get_form(self, request, obj=None, **kwargs):
       form = super(MyModelAdmin, self).get_form(request, obj, **kwargs)
       form.base_fields['your_field_name'].initial = 'abcd'
       return form

did you try simply adding it to a string?

reverse("admin:...")+"&fieldname=value"

you may need to use formating like this

return HttpResponseRedirect('%s%s'%(reverse("..."), '&field=value'))

depending on what your values are, you may need to also use a uri encoding routine (there are many ways to do this).