California Assembly Bill 32 requires effective statewide greenhouse gas (GHG) reduction strategies. This report summarizes the results of six studies--developed to inform California policy--that review the latest science and economics of GHG mitigation opportunities in California's agricultural sector. Specifically, the report examines the potential for annual GHG reductions in cropland, rangeland, and manure management systems and through emissions-targeted optimization of feed for dairy animals. Among the examined practices, dairy manure management appears to provide the largest emissions reduction opportunity at the lowest cost per ton, but economic and other hurdles must be overcome to realize it. Other mitigation activities could yield relatively large per-acre reductions but on relatively small acreage. Yet other activities could be widely implemented, but their potential effectiveness is uncertain. More data on the GHG reduction potential and costs of management practices in California agriculture and a better understanding of adoption barriers are needed.