Magento 1.9.x module that adds a category attribute for cms blocks that can be placed at the bottom of a category.
Download or clone, install in your Magento 1.9.x, log in and refresh cache and indexes. Create a cms static block with text for the specific category where you want to add this block at the bottom. Save and go to your category. Under the tab "Display Settings" of your category you should be able to select a "CMS Block" and directly below that a "CMS Block (bottom)". If not, be sure to clear cache and reindex.