Evaluating Cover Crop Mulches for No-till Organic Production of Onions

Emily R. Vollmer^1*, Nancy Creamer¹, Chris Reberg-Horton² and Greg Hoyt³

Abstract
Cover crops of foxtail millet ‘German Strain R’ [Setaria italica (L.) Beauv.] and cowpea ‘Iron & Clay’ [Vigna unguiculata (L.) Walp.] were grown as monocrops (MIL, COW) and mixtures and compared with a bare ground control (BG) for weed suppression and nitrogen (N) contribution when followed by organically managed no-till bulb onion (Allium cepa L.) production.

Experiments in 2006–2007 and 2007–2008 were each conducted on first-year transitional land. Mixtures consisted of cowpea with high, middle, and low seeding rates of millet (MIX-70, MIX-50, MIX-30). During onion production, each cover crop treatment had three N rate subplots (0, 105, and 210 kg N/ha) of surface-applied soybean meal [Glycine max (L.) Merrill].

Cover crop treatments COW and BG had the greatest total marketable onion yield both years. Where supplemental baled millet was applied in 2006–2007, onion mortality was over 50% in MIL and MIX and was attributed to the thickness of the millet mulch.

Nitrogen rates of 105 and 210 kg N/ha increased soil mineral N (NO3^-; and NH4⁺) on BG plots 2 weeks after surface application of soybean meal each year, but stopped having an effect on soil mineral N by February or March. Split applications of soybean meal could be an important improvement in N management to better meet increased demand for N uptake during bulb initiation and growth in the spring.

Source
HortScience (2010) 45: 61-70


Author Locations & Affiliations
(1) Department of Horticultural Science, North Carolina State University, Campus Box 7609, Raleigh, NC 27695
(2) Department of Crop Science, North Carolina State University, Campus Box 7620, Raleigh, NC 27695
(3) Department of Soil Science, North Carolina State University, 455 Research Drive, Mills River, NC 28759
* Corresponding author, E-mail vollmer.emily@gmail.com


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Posted February 2010