The features have all been dated to between 2000 BC and 1900 AD.
Their discovery will help the National Trust conserve the estate and decide where to plant some 75,000 native British trees in the next few months.
The survey was carried out in February this year over a 22 square mile section of the 5,431 hectare (13,420 acre) estate.
It was the biggest survey the conservation charity has ever carried out.
The discoveries shed new light on the estate’s rich agricultural history and the farming practices that were abandoned in the 18th century by former owner Sir Walter Blackett, who introduced a new and “rational” way of efficient farming.