<i>Crotalaria juncea</i> Genotype Biomass Accumulation in Northern Semi-Arid and Humid-Continental Climates

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. Seeds available for production are 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 also variations in genotype performance is critical for production management. We evaluated the growth and biomass accumulation of four genotypes (KMB1, KMB2, Thailand Original Sunn, and ‘Tropic Sunn’) of sunn hemp grown in northern semi-arid and humid-continental environments, Wyoming (Adams ‘22 and ‘23 (irrigated), Wyarno ‘23 (rainfed)) and Minnesota (Morris ‘22 and ‘23), USA. Thailand Original Sunn had the fastest growth rate (height over time) but the slowest canopy closure (NDVI over time), while KMB1 had the slowest growth rate but the 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 the genotype did not have a significant effect on biomass accumulation, the environment affected not only growth but also biomass accumulation. At 60 DAP, the sunn hemp biomass averaged 1836, 489, 2459, 3334, and 731 kg ha−1 in the Adams ‘22, Adams ‘23, Morris ‘22, Morris ‘23, and Wyarno ‘23 environments, respectively. At 90 DAP, the sunn hemp biomass averaged 6459, 4573, 7979, 7403, and 2220 kg ha−1 in the Adams ‘22, Adams ‘23, Morris ‘22, Morris ‘23, and Wyarno ‘23 environments, respectively. The 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 support the hypothesis 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.

Keywords

• <i>Crotalaria juncea</i>
• sunn hemp
• genotype
• biomass