Conservation Assistance Loan Act of 2018 This bill establishes a Department of Agriculture (USDA) nonrecourse conservation assistance loan program. Under the program, farmers who receive loans must meet certain conservation requirements, including: (1) complying with applicable conservation and wetland protection requirements under the Food Security Act of 1985, (2) using a reduced tillage method and nutrient management practices, and (3) planting a cover crop. (Under a nonrecourse loan, a farmer pledges a commodity as collateral and may deliver the pledged collateral to USDA to repay the loan.)