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Please share your cover crop experiences with all of us. What are your experiences with cover crops? Which ones provide good biomass in your soils? What system do you use to calculate the nitrogen return or credit? Here are some experiences from Mary Howard and Klaus Martin (great diverse sustainable farmers in NY) (From SANET-MG listserv) I have used red clover as my main nitrogen source for many years. When I first converted to organic, clover grew rampantly producing more than 400#/acre of N on the best fields including the growth that took place in the wheat or spelt crops that the clover had been seeded into. As soil nitrogen increased, the growth of clover has slowed until now we get between 50# and 100# in the fall and up to 150# in the spring depending on when it is plowed. Not all of this nitrogen is from recent fixation. Legumes respond to high levels of soil nitrogen by fixing less new nitrogen. I think much of the spring growth may have reused nitrogen that had been fixed in the previous fall and incorporated into the new spring growth. Our challenge in the Northeast is to get the nitrogen to mineralize at the time the crop needs it. We have had so much cold wet weather in May and early June of the past 7 years that nitrogen is not mineralized fast enough to meet the needs of both the crop and the residue breakdown until the soil becomes warmer. I used a small amount of Chilean nitrate last year (12# N/acre) in the starter to help the early corn and it seemed to make a big difference. Yields were up to 40 bushels per acre higher where I used the extra N. If your P index allows it or where it is low enough so that extra P is needed, manure could also supply part of your N requirement. Be careful if you use layer manure. It contains a large amount of calcium and lime must be reduced to account for that. The big challenge with organic N is timing mineralization to coincide with crop demand. If N is very deficient, grow crop that needs less and wait until you have enough to produce corn unless you have a lot of cheap manure. > Date: Tue, 30 Jan 2007 17:16:32 +0000 > From: craig mcsparran <[log in to unmask]> > Subject: clover nitrogen contributions to corn > > <html><div style='background-color:'><P> </P> > <P>Sanet</P> > <P>I have a question regarding the amount of nitrogen that can be > contributed from a winter annual crimson clover, grown prior to corn. > I believe a standard contribution would be between 50-100# > of nitrogen from a good stand of crimson clover plowed down prior to planting corn in the mid-Atlantic area. > However if the clover was chopped for forage and only the root mass of > the clover was left, would a substantial amount of the nitrogen still > be available for the following crop or was most of the available > nitrogen removed in the above ground biomass?</P> <P>If anybody has > had experience using Chilean nitrate as a supplemental source of N for > organic corn I would like to hear your thoughts on this practice.</P> > <P>Craig McSparran</P> Vicki Morrone Organic Vegetable and Crop Outreach Specialist Michigan State University C.S. Mott Sustainable Food Systems 303 Natural Resources Bldg. East Lansing, MI 48824 517-353-3542 517-282-3557 (cell) 517-353-3834 (fax) http://safs.msu.edu/ http://www.mottgroup.msu.edu/ If you would like to access previous postings to the Mich-Organic listserv you can copy and paste the following URL into your browser address bar http://list.msu.edu/archives/mich-organic.html