Justice for Black Farmers Act of 2021 This bill directs the Department of Agriculture (USDA) to provide a variety of assistance to address historical discrimination and disparities in the agricultural sector. For example, the bill establishes an equity commission in USDA to examine discrimination by the agency against Black farmers and ranchers and recommend actions to end the systematic disparities in the treatment of Black farmers and ranchers. USDA must also establish a Farm Conservation Corps to provide young adults who are from socially disadvantaged groups with the skills necessary to pursue careers in farming and ranching. The bill provides funding for historically Black colleges and universities to commence and expand courses of study that are focused on careers in agriculture or related disciplines. The bill also increases the authorization of appropriations for a program to resolve issues relating to ownership and succession on farmland. Additionally, it expands credit assistance for socially disadvantaged farmers and ranchers. Further, the bill (1) establishes that a minimum of 50% of a covered packer's (not including a packer that owns only one livestock processing plant) daily volume of livestock slaughter must be purchased through spot market sales from nonaffiliated producers; (2) increases funding for the Local Agriculture Market Program; and (3) gives priority to socially disadvantaged farmers and ranchers for conservation technical assistance, the Conservation Stewardship Program, and the Rural Energy for America Program.