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Nitrogen fertilization is a common practice for sustaining forage production in forage systems in southeastern United States. Warm‐season annual legumes may be an alternative forage to warm‐season perennial grasses that do not require N fertilization. Sunn hemp (Crotalaria juncea L.) is a fast‐growing, warm‐season annual legume native to India and Pakistan. The objective of this 2‐year study was to assess the herbage accumulation (HA), atmospheric N2 fixation (ANF) and nutritive value of sunn hemp. Treatments were the factorial arrangement of two sunn hemp cultivars ("Crescent Sun" and "Blue Leaf"), three seeding rates (17, 28 and 39 kg seed/ha) and seed inoculation (inoculated or non‐inoculated seeds), distributed in a randomized complete block design with four replicates. Crescent sun had greater HA (3,218 vs. 1764 kg DM/ha) and ANF (41 vs. 25 kg N/ha). Blue leaf had greater crude protein (CP) (188 vs. 176 g/kg) and in vitro digestible organic matter (IVDOM) concentrations (564 vs. 531 g/kg) than crescent sun. Non‐inoculated seed had greater CP than inoculated seed, 188 and 177 g/kg, respectively, and inoculation did not affect HA. Intermediate seeding rate (28 kg/ha) decreased HA (2002 kg DM/ha), while HA from high and low seeding rates (17 and 39 kg/ha, respectively) did not differ (2,863 and 2,615 kg DM/ha respectively). Planting non‐inoculated crescent sun at 17 kg/ha seeding rate is a feasible management practice to produce sunn hemp in subtropical regions; however, inoculation should always be recommended for proper establishment. [ABSTRACT FROM AUTHOR]