; and (ii) the Director of the National Science Foundation. (3) High-carbon-input crop phenotypes (A) In general The Secretary shall carry out development of advanced cultivars and forestry crops with enhanced carbon uptake and retention. (B) Collaboration The Secretary shall carry out the activities under subparagraph (A) in collaboration with the Chief of the Forest Service. (4) Cultivation system optimization (A) In general The Secretary shall carry out research on regionally specific best practices for soil health and carbon retention at not fewer than 10 sites, including at least 1 site in a tropical region. (B) Consideration The Secretary shall consider co-locating sites described in subparagraph (A) with sites used by the National Resource Inventory of the Natural Resources Conservation Service, the Long Term Ecological Research Network, the National Ecological Observatory Network, and the Forest Inventory and Analysis Program. (5) Agroforestry The Secretary shall carry out research on integrating regionally appropriate trees and shrubs into crop and animal farming systems as a carbon dioxide removal practice at no fewer than 5 geographically diverse test sites. (6) Perennial plants and marginal lands The Secretary shall carry out research into the use of perennial plants for carbon dioxide removal, including research on— (A) genetic traits; (B) improved soil carbon sequestration modeling; (C) perennialization of useful annual crops