Agriculture Data Act of 2018 This bill amends the Food Security Act of 1985 to require the Department of Agriculture (USDA) to collect, review, analyze, and disseminate certain data on the impact of conservation practices on farm and ranch profitability, including the effect on crop yields, soil health, and other risk-reducing factors. The bill also requires USDA to establish a conservation and farm productivity data warehouse to make the results of the data collection and analysis available to academic institutions and researchers. USDA must also provide technical assistance, including through internet-based tools, based on the analysis conducted and other relevant data, to assist producers in improving sustainable production practices that increase yields and enhance environmental outcomes.