The soil in my backyard has very few rocks but the clay is so hard and dense it may as well be a brick wall.
What is the purpose of planting clover?
(It’s the bacteria in the roots that do the actual nitrogen chemistry.)
"If you mix sand into clay, the clay particles will fill in all the open spaces between the sand particles and often the clay will act as a ‘glue’ sticking all particles together, ultimately resulting in a more dense soil."