As a warm season cover crop legume, Sunn Hemp increases soil organic matter, provides nitrogen, grows in low fertility sandy soils, and does not harbor most types of nematodes most destructive to crops in North America, generally found in sandy soils in Southern growing regions.
Sunn Hemp is native to the tropics, but grows in North America as a summer annual. It can produce over 5,000 pounds of biomass and up to 140 pounds of nitrogen per acre, depending on conditions.
Because of its fast growth, Sunn Hemp only needs 8 to 12 weeks of frost-free growth conditions to achieve good results. This makes it an excellent choice where there is a relatively short window following cash crop harvest in the fall and the onset of winter.
Where conditions are favorable, Sunn Hemp can provide the benefits of a winter legume prior to a killing frost in the fall, and also in the summer after the winter crop has been harvested.
Sunn Hemp grows rapidly and achieves economic value as a cover crop in about 60 days. Sunn Hemp is killed by the first frost. The management cue for termination (burn down) is when the first flower buds begin to appear.
Sunn Hemp adds significant nitrogen to depleted soils, such as following small grain harvest, as a break crop in sugar cane production, and with vegetables grown in loose sandy soils, where it also adds up to two and a half tons of organic matter. Sunn Hemp nodulates readily with native cowpea type rhizobia. Plant anytime after last threat of spring frost. For maximum benefit, plant a minimum of 8 weeks before average first frost in the fall.
Requires inoculant, cowpea type is recommended
Suggested seeding rates:
- Drill (7.5″ rows): 15 lbs/acre
- Broadcast/Aerial: Not recommended
- Precision plant at 9 lbs/acre in 15″ rows or 5 lbs/acre in 30″ rows (4″ in-row spacing). Kinze Brush Meter with Backing Plate – 60 Cell Sugar Beet Plate
Approx. seeds/lb.: 15,000
Seeding depth: Seed ½ to 1″ deep as required for good seed-to-soil contact with adequate moisture present on a weed-free bed. Soil pH 5.5 to 7.5.
Ave. Emergence time: 3-7 days
Planting window: Anytime after the last threat of spring frost. For maximum benefit, plant a minimum of 8 weeks before average first frost in fall. Soil temps should be at least 60° F. or warmer.
Control: Control (terminate) at first flower for maximum benefit, and before it becomes fibrous and difficult to manage.