Laying a new lawn - can I mix bark with topsoil?

I'm converting a children's barked play area to lawn this week. I've removed the bark and membrane in preparation for the topsoil. Some of the bark I removed is quite fine and I was wondering if I could mix it with the topsoil before laying the turf? Does anyone know if I can do this? It seems a shame not to reuse the finer bark in some way... Many thanks

 

Its not advisable. A small amount won't matter but too much and as the bark rots it may cause a problem like mold.

 

As well as leaving the lawn bumpy,- as the little pockets of bark finish decomposing it will sink .

 

It will encourage fungi as said previously