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Title: Planting date and seeding rate effects on sunn hemp biomass and nitrogen production for a winter cover crop

Author
item Balkcom, Kipling
item MASSEY, JESSICA - Auburn University
item MOSIJIDIS, JORGE - Auburn University
item Price, Andrew
item ENLOE, STEPHEN - Auburn University

Submitted to: International Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2011
Publication Date: 9/1/2011
Citation: Balkcom, K.S., Massey, J.M., Mosijidis, J.A., Price, A.J., Enloe, S.F. 2011. Planting date and seeding rate effects on sunn hemp biomass and nitrogen production for a winter cover crop. International Journal of Agronomy. Article 237510. Available: http://www.hindawi.com/journals/ija/2011/237510/. https://doi.org/10.1155/2011/237510
DOI: https://doi.org/10.1155/2011/237510

Interpretive Summary: Sunn hemp is a tropical legume that produces plant biomass and nitrogen (N) quickly, but seed for the traditional cultivar is very hard to obtain and expensive if available. Scientists with USDA-ARS located at the National Soil Dynamics Laboratory in Auburn, AL in cooperation with Auburn Univ. examined the agronomic performance of a new sunn hemp cultivar breed to produce seed in the Southeast and determine how much N is available to a subsequent rye winter cover crop in east-central Alabama from 2007 to 2009. Different sunn hemp planting dates and seeding rates were examined following corn and wheat harvests. Sunn hemp biomass production was inconsistent but did relate to the growing season. Neither planting date nor seeding rate affected rye biomass production, but rye biomass averaged over both planting dates following wheat/sunn hemp averaged 43% and 33% greater than rye following fallow. Rye biomass following corn/sunn hemp was equivalent to fallow plots, which was related to the growing season. This research indicates early planting dates are recommended for sunn hemp with seeding rates between 17 and 34 kg/ha to maximize biomass and N production.

Technical Abstract: Sunn hemp (Crotalaria juncea L.) is a tropical legume that produces plant biomass and nitrogen (N) quickly. Our objectives were to assess the growth of a new sunn hemp cultivar breed to produce seed in a temperate climate and determine the residual N effect on a subsequent rye (Secale cereale L.) winter cover crop in east-central Alabama from 2007 to 2009. Plant populations, plant height, stem diameter, biomass production, and N content were determined for two sunn hemp planting dates, following corn (Zea mays L.) and wheat (Triticum aestivum L.) harvest, across different seeding rates (17, 34, 50, and 67 kg/ha). Rye biomass production was measured each spring following the sunn hemp growing season. Sunn hemp biomass production was inconsistent across planting dates, but did relate to growing degree accumulation. Seeding rates had little effect on sunn hemp biomass production. Nitrogen concentrations were inversely related to biomass production, and subsequent N contents corresponded to biomass levels. Neither planting date nor seeding rate affected rye biomass production, but rye biomass averaged over both planting dates following wheat/sunn hemp averaged 43% and 33% greater than rye following fallow. Rye biomass following corn/sunn hemp was equivalent to fallow plots, which can be attributed to reduced growing degree accumulation. This research indicates early planting dates are recommended for sunn hemp with seeding rates between 17 and 34 kg/ha to maximize biomass and N production.