i'm trying to improve the soil quality in my yard, it's hard and clay-like and roots have a hard time going down below like 4 cm. i have cow patties, rice hulls, rinsed coco coir and some cardboard.

currently the plan has been to mix up the patties and rice hulls and bury that below ground (completed already), then mulch with the coir + hulls + patties, then finally cover with cardboard. the yard is small so not much cardboard involved. i'm growing cucumbers, tomatoes, peppers, eggplants and beans this year, they should have been in the ground already but i wanted to grow from seed and my cats got to the sprouts. so i gotta get new ones

please tell me what i am missing or what i could do better.