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This article in AJ

  1. Vol. 99 No. 6, p. 1448-1457
    Received: Oct 23, 2006

    * Corresponding author(s): harry.schomberg@ars.usda.gov
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Potential for Using Sunn Hemp as a Source of Biomass and Nitrogen for the Piedmont and Coastal Plain Regions of the Southeastern USA

  1. Harry H. Schomberg *a,
  2. Nicole L. Martinib,
  3. Juan C. Diaz-Perezb,
  4. Sharad C. Phatakb,
  5. Kipling S. Balkcomc and
  6. Harbans L. Bhardwajd
  1. a USDA-ARS, J. Phil Campbell, Senior, Natural Resource Conservation Center, Watkinsville, GA 30677
    b Dep. of Horticulture, Univ. of Georgia, UGA-Tifton Campus, Tifton, GA 31793
    c USDA-ARS, National Soil Dynamics Lab., Auburn, AL 36832
    d New Crops Program, Virginia State Univ., Petersburg, VA 23806


The tropical legume sunn hemp (Crotalaria juncea L.) could be a valuable green manure/cover crop for vegetable producers in the southeastern USA because of its rapid growth and large N2 fixing ability. Planting and termination date effects on biomass and N accumulation are relatively unknown for the region, but would help producers manage sunn hemp between summer and winter cash crops. We determined sunn hemp biomass and N content at 30, 60, 90, and 120 days after planting (DAP) for four planting dates (mid-April to mid-July) at a Piedmont and a Coastal Plain location in Georgia. Maximum biomass at a given DAP was produced from May and June plantings in the Piedmont and from April and May plantings in the Coastal Plains. Maximum biomass and N ranged from 8.9 to 13.0 Mg ha−1 and 135 to 285 kg ha−1, respectively. An equation for estimating sunn hemp biomass as a linear function of cumulative degree days (CDD) and cumulative solar radiation (CSR) was verified with independent data from Alabama, Florida, and Virginia. A similar equation for estimating N content as a quadratic function of CSR was not as accurate but still might be useful. Sunn hemp can fit well into short-rotation sustainable vegetable production systems in the Southeast, and these equations can be used by producers to make reliable estimates of sunn hemp biomass production.

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