Mesh interferes with the texture of a plane So I have a simple scene in blender, there is a track situaded in a grass field. However it seems that the road somehow inteferes with the plane. If I (re)move the track it solves the problem. The same happens with a little car I have that isn't shown. The grass texture is a seamless grass texture 1024x1024 if I recall correctly.

I've chequed the bounding boxes and wireframes and everything seems good.
You can download the .blend file below.
I don't know what you mean by the track interfering... but the texture mapping for the grassy plane is messed up.

First of all, your plane has been scaled in Object mode.

select Select the plane and press CtrlA and select Apply Rotation and Scale

(More on why you always want to apply your scale here and here) 

Next: 
Your plane has no UV map, so blender will not know how to map the image.

Go to top view. , enter edit mode select all (A) press U to unwrap the texture. 





(note that I changed the number of repeats for illustrations purposes...