Just press your middle mouse button on the dirt once you've run out of the stack that's in your hand, and it will bring another stack from your inv.

 

Doesn’t that only work in creative?

 

Nope, I just tested it, as long as you have the blocks in your inventory, it will bring them into your hand.

 

Pretty sure you could write a macro that would /stack just before you run out of dirt cause im pretty sure it just fill up stacks that arent full (hotbar first)
Though the chat messages might be annoying.

 

In creative, it creates the block in your inventory, but in survival it brings the next stack of items from left to right to your currently selected space, and if you have a tool in your hand, unless your whole row is full of tools, it will move instead a stacked item and place it there, as well as move your selected spot on the hotbar

It's a mod, but there's inventory tweaks that has this mechanic. Idk if it's allowed though.

 

You just want a macro to /stack every 30 secs? I'll give it a go for you and forum pm you it :p