Grass airfields act like having tarmac base

[skywalker22]

I just landed on some of the airfield with a grass on it, 1st ot all, I was surprised on the hard landing like there would be a tarmac base, and then when I started braking, there was that sound of tire braking on tarmac with my Bf-109. Would be nice to fix that, having grass or some soil, which would also act like one. 

And another thing, the grass blades should be shorter on the airfield, looks strange having 50cm or more tall grass sticking out of the ground.