EQIP Improvement Act of 2018 This bill amends the Food Security Act of 1985 to modify the Department of Agriculture (USDA) Environmental Quality Incentives Program (EQIP). (EQIP provides financial and technical assistance for agricultural producers and land owners to implement certain conservation practices.) The bill modifies EQIP to: reduce the maximum federal cost-share from 75% to 40% for specified practices, repeal the requirement for at least 60% of the funds made available for EQIP payments to be targeted at practices relating to livestock production, and reduce the five-year EQIP payment cap from $450,000 to $150,000. The bill also requires USDA to: (1) coordinate the program with the conservation effects assessments carried out by USDA, and (2) revise the guidance issued to states for allocating funds to require data regarding environmental concerns to be used as a primary factor to prioritize projects. USDA must prioritize EQIP applications that consist only of the performance of certain land management or vegetative practices that are a cost-effective means of addressing the most pressing impairments that threaten to degrade or impair water quality, water quantity, soil or related natural resources within a local watershed, or a specific natural resource boundary.