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market-farming - Re: [Market-farming] available N from soil organic matter

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  • From: road's end farm <organic101 AT linkny.com>
  • To: Market Farming <market-farming AT lists.ibiblio.org>
  • Subject: Re: [Market-farming] available N from soil organic matter
  • Date: Sun, 9 Apr 2006 14:08:28 -0400


On Apr 8, 2006, at 12:27 PM, Mike Emers wrote:

Does anyone know a rough rule of thumb for the amount of nitrogen
available from the percent organic matter in the soil? I know there are
many variables including soil moisture and temperature but I'm looking
for a ballpark figure.

Huh. I thought I had this, but I can't find it. I know it's around somewhere.

I did. however, find an old flyer from MOFGA which says, "reduce nitrogen recommendation by 10% for each 1% organic matter reported in soil test".

And I have a table from Cooperative Extension titled: "Book values for N supply from good full grown sods":
(the total amount doesn't become available at once;a they figure 55% release in the first year, 12% in the second, 5% in year 3)

If 0% legume in the sod: total organic N 150 lb/acre; year 1 release 83 lb; year 2, 18 lb; year 3, 8 lb
1-25% legume: total N 200 lb/acre; year 1, 100 lb; year 2, 24 lb; year 3, 10 lb
25-50% legume: total N 250 lb/acre; year 1, 138 lb; year 2, 30 lb; year 3, 13 lb
Greater than 50% legume: total N 300 lb/acre; year 1, 165 lb; year 2, 36 lb; year 3, 15 lb

So if you're tilling in a sod or cover crop, or did so recently, that should give you some idea of how much you're replacing. You wouldn't want to keep taking it out of the organic matter without replacing it somehow, in any case.

-- Rivka; Finger Lakes NY, Zone 5 mostly
Fresh-market organic produce, small scale



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