Crotalaria Juncea L. Cv. IAC-1 for Livestock Feed and Seed Production in Low-External-Input Mixed Crop/Livestock Production Systems for the Tropics.

Crotalaria juncea L. is a tropical warm season legume that is growing in popularity in the United States (U.S.) as a cover crop and green manure crop that can contribute nitrogen and organic matter to the farming system.  It also serves as an important fiber crop, has use as a livestock forage, and may serve as a valuable bioenergy feedstock.  Due to the limited availability of commercial C. juncea seed in the U.S., this preliminary trial investigates C. juncea cv IAC-1 for livestock forage production and commercial seed production under low-external-input farming conditions.  A feasibility study was conducted on St. Croix in the U.S. Virgin Islands to test two seed production systems. Test plots were broadcast seeded and then rolled with a culti-packer.  No inputs were applied for the production of the crop.  The first system (SYS1) measured seed production at 2 harvest dates (160 days after planting (DAP) and 191 DAP).  The second system (SYS2) combined biomass removal through a hay harvest 55 DAP and then seed harvest on the C. juncea  re-growth at 195 DAP or 140 days after forage removal.  SYS2 produced a mean biomass yield of 4,741 kg/ha of forage on a dry matter basis which was dried, bailed for hay, and subsequently fed to sheep in a separate feeding trial.  Preliminary results indicate that SYS2 produced fewer seed pods per plant (21 ±2.8, p<0.05)) and had fewer seeds per pod (4.7 ± 0.2, p<0.0001)) than either harvest 1 (30 ±2.5 and 6.6 ±0.2, respectively) or harvest 2 (29 ±2.5 and 6.4 ±0.2, respectively) from SYS1.  At the time of seed harvest, SYS2 had higher plant density with 67 plants /m² than harvest 1 (160 DAP) or 2 (191 DAP) from SYS1 with 40 and 41 plants/m², respectively (p<0.0001).  Total seed yield was highest in harvest 1 of SYS1 producing 3,153 kg/ha ±270 which was statistically similar with harvest 2 that produced 3,115 kg/ha of seed from SYS1, but was greater than the seed harvest in SYS2 with 1,040 kg/ha of seed (p<0.0001).   Results of this study indicate that Crotalaria juncea cv. IAC-1 can be grown in the tropics under low-external-input conditions to produce a robust seed crop, and that farmers can harvest C. juncea  forage for livestock production and still produce and harvest a seed crop for future planting or for sale as a  potential cash crop.  Additional research trials will follow to further investigate the use of C. juncea as a multi-purpose crop in low-external-input mixed crop/livestock systems.