Farmland Security Act of 2023 This bill authorizes increased civil penalties for violations of the Agricultural Foreign Investment Disclosure Act of 1978 (AFIDA) and increases Department of Agriculture (USDA) oversight and research into foreign investment in agricultural land. (AFIDA and the regulations that implemented the act require foreign investors who acquire, transfer, or hold an interest in U.S. agricultural land to report such holdings and transactions to USDA.) In general, the bill allows USDA to determine an appropriate civil penalty amount for an AFIDA violation by removing the cap that currently prohibits the civil penalty from exceeding 25% of the fair market value of the interest in the land. The bill provides an exception for a shell corporation (i.e., a corporation, company, association, firm, partnership, society, joint stock company, trust, or estate that has no or nominal operations). An AFIDA civil penalty for a foreign-owned shell corporation must be 100% of the fair market value of the interest in the agricultural land associated with the violation. The penalty does not apply if the shell corporation remedies a defective filing or failure to file within 60 days of USDA providing notice. USDA must conduct annual compliance audits of at least 10% of the reports. Further, USDA must provide state and county-level personnel annual training in identifying agricultural land for which a report must be submitted. USDA must also annually conduct research and submit a report to Congress on foreign investment in agricultural land, including trends in the purchase of U.S. agricultural land by foreign-owned shell corporations.