An appropriate and functional transportation network forms an essential basis for the competitiveness of agricultural and forestry enterprises as well as for the preservation of liveable, rural areas. Through structural changes in the field of agriculture, which become obvious e. g. by the increasing size of farms and agricultural machinery, the demands on the existing agricultural road network have changed significantly. Machines have become significantly heavier, larger and faster and due to increasing farm sizes, trans-regional transportation becomes more and more important. Considering these changed requirements, in numerous Federal States of Germany initiatives for designing core transportation networks have been launched. The goal of these initiatives is to design core road networks as needs-based, multifunctional path systems across regions. The core road networks consist of existing roads with a high relevance for agricultural transportation, which will be modernized to meet current and future needs of agriculture. Identifying these roads is a challenging task for planners. In this paper, we present digital methods for supporting planners in designing agricultural core road networks. These methods are based on a Digital Twin of the cultivated landscape. One of the core concepts of the Digital Twin is the coupling of a comprehensive, spatiotemporal information model of the cultivated landscape with complex analytical methods. Besides monitoring the current state of the agricultural landscape, the concept can also be used to assess the impact of design proposals in various aspects. This article describes the new digital methods and their application in a real planning process. Furthermore, it discusses the relation of the Digital Twin concept with the geodesign paradigm.