Why is it so much harder to keep up speed on your bike when you’re in the grass than when you’re on dirt or hard soil?

Question

It feels like the tiny little speck of grass shouldnt bring that much friction. Is there something I’m missing?

In: 2

Answer 1

Pavement, and hard surfaces are much smoother than grass.
Grass is also softer than hard surfaces so you sink a bit. When sinking you have to fight against gravity to roll up out of the ever moving depression under the tires. This expends more effort.