Definitely a good thing to do.
If you don't want to cover the land, another good thing to do with large quantites of cardboard is pack the broken-down boxes tightly into one box, with all the corrugations running vertically. Put it behind the shed and wee into it every couple of days. Makes brilliant compost.
Small quantities, of course, can be torn up and put on the compost heap.
The worms seem to especially love corrugated cardboard. It’s always good to get them working away for you. As the card or paper disintegrates it adds its carbon directly into the soil. Then the grass clippings get drawn down and eaten as well. The improvement to the soil is tremendous. Initially, our soil was very poor with hardly a worm to be found. Not surprising when there’s little organic matter for them to eat. After mulching the worm population increases and the rest of the soil ecology along with them. They’re busy concentrating nutrients in their gut so worm casts are perfect for plants.
The tunnels they create are also extremely valuable in this process, enabling oxygen to get down further into the soil. This aids both the plant roots directly and fuels the aerobic economy of the soil. It’s a slow process but after just three years the difference in the soil is obvious. It’s darker, deeper, and richer.