class MigrateNotesToEditorsOnEdition < ActiveRecord::Migration
  def up
    Edition.where('notes_to_editors !=""').each do |edition| 
      edition.update_attribute :body, "#{body}\n\n##Notes to editors\n\n#{edition.notes_to_editors}"
    end
    remove_column :editions, :notes_to_editors
  end

  def down
    add_column :editions, :notes_to_editors, :text
  end
end

class MigrateNotesToEditorsOnEdition < ActiveRecord::Migration
  def up
    Edition.where('notes_to_editors !=""').each do |edition| 
      edition.update_attribute :body, "\n##Notes to editors\n\n#{edition.notes_to_editors}"
    end
    remove_column :editions, :notes_to_editors
  end

  def down
    add_column :editions, :notes_to_editors
  end
end

--- 
+++ 
@@ -1,12 +1,12 @@
 class MigrateNotesToEditorsOnEdition < ActiveRecord::Migration
   def up
     Edition.where('notes_to_editors !=""').each do |edition| 
-      edition.update_attribute :body, "\n##Notes to editors\n\n#{edition.notes_to_editors}"
+      edition.update_attribute :body, "#{body}\n\n##Notes to editors\n\n#{edition.notes_to_editors}"
     end
     remove_column :editions, :notes_to_editors
   end
 
   def down
-    add_column :editions, :notes_to_editors
+    add_column :editions, :notes_to_editors, :text
   end
 end
Correct last migration not to remove the body

Also added proper 'down' method
