Dear Robert, when we are single digging soil we use a tarpaulin! This goes back years as they are really cheap from Army surplus stores. As they are waterproof it does not matter what you get on them, so can withstand our British weather, which is not easy! They are also massive so you can cut them to any size you so wish. Of course they only come in one colour and that is Army green!
Regards form a very wet England.
Neil.