With our red clay in Oklahoma, horticulture division suggests adding gypsum to soften the clay along with aged compost that incorporates shredded leaves and grass clippings.Yup, it's like that in much of central Texas too, either granite or limestone. Even around here, some people trying to put in pools or underground structures like basements or storm shelters get shell shock from the price of excavation after their site has been assessed. The clay soil is fertile, but a long term project for gardeners. I'm using raised beds as well as working on loosening the tilth of my native soil in one area using compost and a little sand. One of the reasons for keeping the hens is their compostable litter and droppings.
I also double dig when I turn my 12 inch high raised beds.every other year. This opens up the clay under the beds to the roots of my veggies and helps improve drainage and tilth.
I use the clean out from the deep litter in the hen house in my compost too. The soiled wood shavings from the brooder room becomes mulch and gets turned into the beds in the fall.