Sunn Hemp for Alternative Forage Production: Field Management and Forage Characteristics in the Northeast.

Tropical annual Crotalaria juncea, common name Sunn Hemp (SH), is of increasing interest to farmers for its dual-purpose potential as an N-fixing cover crop and alternative forage. Despite interest, information in the northeast U.S. is scarce. Preliminary research (2013-2015) verified SH grows successfully in the temperate climate of Massachusetts. In the summer of 2016 and 2017, four replication of SH were planted on three dates (7/12, 7/26, 8/9) in a random block design to identify ideal planting and harvest dates provisory to a grower’s desired use. The effect of date of planting (DOP) on dry matter (DM) production, rate of growth, N-fixation, and suitability as forage was assessed. From 30-90 days after planting (DAP), plants were harvested every 10 days; harvest ceased after the first frost and winterkill. A split-plot treatment assessed the effect of weeds on growth over time. Weed pressure did not significantly affect DM regardless of DOP or DAP. As expected, DAP (nested in DOP), had a highly significant effect on DM. DOP was also highly significant, with SH planted on 7/12 producing up to 14 Mg ha^-1 DM suitable for green manure before the first frost, while the 7/26 and 8/9 DOP produced just 7 Mg ha^-1 and 2 Mg ha^-1, respectively. The 7/12 DOP allowed for either three cuttings and 3 Mg ha^-1 DM for forage, or 2 cuttings and 5.5 Mg ha^-1 DM; a yield and quality trade-off is expected. The 7/26 planting allowed for only two cuttings and 2 Mg ha^-1 DM. Substantial amounts of N were produced, up to 280 (DOP1), 210 (DOP2), and 55 (DOP3) kg ha^-1 . SH demonstrates remarkable potential for dual-purpose use in the Northeast as both alternative feed and fertilizer, and this work establishes the foundation necessary to support further research.