Sunn hemp planting date effect on growth, biomass accumulation, and nutritive value in southeastern Wyoming
Carrie A. Eberle, Lauren Shortnacy
Abstract
Abstract Sustainablesuccess of the Northern High Plains (NHP) crop and livestock industry is limited by market accessibility, infertile soils, short growing seasons, and availability of high nutritive value, low‐cost feed. Adoption of the tropical legume, Crotalaria juncea L. (commonly known as sunn hemp), into NHP cropping systems could improve the sustainability of the rotation by fitting into summer growing windows and being used as a hay alternative. Rainfed and irrigated studies were conducted in Lingle, WY, to determine the target planting date for sunn hemp in the NHP. Later planting day of year was correlated with increased percent establishment in the rainfed study but had no effect in the irrigated study. In both irrigated and rainfed studies, planting between 8 June and 18 June maximized biomass accumulation. Biomass accumulation 60 d after planting ranged from 0.2 to 5.1 Mg ha –1 in the rainfed study and 1.2 to 4.2 Mg ha –1 in the irrigated study. For both irrigated and rainfed studies, the nutritive value of sunn hemp was high with crude protein greater than 220 g Kg –1 , acid detergent fiber less than 305 g Kg –1 , neutral detergent fiber less than 331 g Kg –1 , relative feed values above 183, and total digestible nutrients greater than 590 g Kg –1 . Planting date did not affect nutritive value. Sunn hemp grown in the NHP has a 60‐d yield potential 5.1 Mg ha –1 , should be planted between 8–18 June to 60‐d biomass production, and has nutritive value equivalent to supreme quality alfalfa ( Medicago sativa L.) hay.