Crotalaria juncea genotype biomass accumulation in Northern Semi-Arid and Humid-Continental Climates

Authors: Eberle, Carrie; HARRIS, DONNA - University Of Wyoming; JONES, TYLER - University Of Wyoming; FOWERS, BETH - University Of Wyoming; MEALOR, BRIAN - University Of Wyoming

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2024
Publication Date: 10/10/2024
Citation: Eberle, C.A., Harris, D.K., Jones, T.Z., Fowers, B., Mealor, B. 2024. Crotalaria juncea genotype biomass accumulation in northern semi-arid and humid-continental climates. Agronomy. https://doi.org/10.3390/agronomy14102334.
DOI: https://doi.org/10.3390/agronomy14102334

Interpretive Summary: Sunn hemp is a tropical forage legume used as a cover, forage, and fiber crop. There is limited seed of sunn hemp varieties available for production, instead non-specific genotypes are sold for use. As sunn hemp is grown in more diverse locations, it is important to understand how it performs in different environments, and if the non-specific genotypes available to the public differ in their performance. We evaluated the growth and forage yield of four genotypes (KMB1, KMB2, Thailand Original Sunn, and Tropic Sunn) of sunn hemp grown in Sheridan, Wyoming, and Morris, Minnesota, USA. Thailand Original Sunn had the fastest growth rate (height over time) but slowest canopy closure (NDVI over time) while KMB1 had the slowest growth rate but fastest canopy closure. When harvested 45 days after planting, forage yield was the highest for Thailand Original Sunn for all locations. When harvested at 60 and 90 days after planting, forage yield was not different between genotypes. Sunn hemp grown in Wyoming had slower growth rate, slower canopy closure, and lower forage yield than sunn hemp grown in Minnesota. These findings indicate that the non specific genotypes are unlikely to yield differently when harvested after 60 days and that growing conditions will have the largest effect on forage yield. These research findings will benefit producers interested in using sunn hemp as a forage crop and extension educators, researchers, and ag consultants interested in adopting sunn hemp into a cropping rotation or feed ration.

Technical Abstract: Crotalaria juncea (sunn hemp) is a tropical forage legume used as a cover, forage, and fiber crop. Sunn hemp seed production occurs primarily in India because it requires short days to flower and set seed. Seed available for production is typically non-specific genotypes instead of true breeding varieties. As sunn hemp is grown in more locations, understanding not only its performance in different growing conditions, but variation in genotype performance is critical for production management. We evaluated the growth and biomass accumulation of four genotypes (KMB1, KMB2, Thailand Original Sunn, "Tropic Sunn") of sunn hemp grown in northern semi-arid and humid-continental environments, Wyoming and Minnesota, USA. Thailand Original Sunn had the fastest growth rate (height over time) but slowest canopy closure (NDVI over time) while KMB1 had the slowest growth rate but fastest canopy closure. While growth rates varied among sunn hemp germplasm, there were no marked differences in biomass accumulation when harvested at 60 and 90 days after planting. Although genotype did not have a significant effect on biomass accumulation, environment not only affected growth but also biomass accumulation. Growth rate, canopy closure, and biomass accumulation differed when compared between the semi-arid environments and the humid-continental environment, with the humid-continental environment producing faster growth and higher biomass. These findings indicate that genotypes are likely to perform as predicted within growing regions, but there may be room to improve performance in different environments through selective breeding.