I think your topsoil is gone Frankie…. ……that’s probably hindering your biomass production…..Having even a small layer of topsoil over clay makes a big difference……Below is growing on heavy clay and hasn’t had anything special done to it….I mowed it during the summer and then just threw seed out in October…..that’s it…….It has a decent little layer of OM on top though where it hasn’t been tilled…..It also doesn’t get full direct sun all day long so that probably helps hold a little more moisture too…..