Bonus tip: mow everything

Strategic mowing of weedy pasture has been shown to be a great way of controlling many types of annual and perennial weeds. Research by the University of Wisconsin showed one mowing in the growing season (eg when a plant is at a fresh, dense leafy stage, but before flowering) can be enough to manage annual weeds, while multiple mowings of perennial weeds when they are 20-30cm high (again, before flowering) will kill them off. However, some weeds with a creeping root system like Californian thistle (note, in the US this is known as Canada thistle), will require multiple mowings during specific growth periods.

http://host.cals.wisc.edu/renzweedsci/1996/10/04/weedcontrol-in-pastures-without-chemicals/