From the Document: "The farm bill is an omnibus, multiyear law that governs an array of agricultural and food programs. It provides an opportunity for policymakers to comprehensively and periodically address agricultural and food issues. In addition to developing and enacting farm legislation, Congress is involved in overseeing its implementation. [...] Some farm bill programs would expire without reauthorization, such as the nutrition assistance programs and the commodity programs. Without reauthorization, certain basic farm commodities would revert to long-abandoned--and potentially costly--supply-control and price regimes under permanent law dating back to the 1940s. Many discretionary programs would not have statutory authority to receive appropriations. Other programs have permanent authority and do not need reauthorization (e.g., crop insurance) but might be included in a farm bill to make policy changes or achieve budgetary goals."
CRS In Focus, IF11126
Congressional Research Service: https://crsreports.congress.gov/