Keyline design is an intellectual tool to be used in regeneration of soils and agricultural practices. It involves management of water cycle resources and infiltrating the water into the soils on or near the contours of the land, in order to retain the maximum rainfall which arrives at the site. This allows plants and soil organisms to prosper even on desertified landscapes which were degraded by poor management or other natural processes. See Regrarian agriculture on the internet for more holistic details.
Darren Dougherty on Regrarianism on youtube (1:29:19) is a great place to start.