RenewableUK, a trade body for the UK wind and marine renewables industries, provides the answer. (There's no reason for me to believe that the UK's space requirements are different from ours.)
According to them,
To obtain 10% of our electricity from the wind would require ... 0.3% to 0.5% of the UK land area.They go on to say that less than 1% of this area would be used for foundations and access roads and that the other 99% could still be used for farming. By comparison, they say, 1.5% of the UK land area is covered by roads and about 77% is used for agriculture.
Photo: National Renewable Energy Laboratory, Photographic Information Exchange.