Subject: Re: Mulching/Reseeding

From: [email-masked]
Date: Tue, 4 Feb 1997 10:06:41 -0500 (EST)

Thanks Jack:

I knew that there was a good reason.

Dan Hemenway

In a message dated 2/3/97 1:59:45 PM, [email-masked] (jack rowe)
wrote:

>A basic answer to the question of when to cut green manures for greatest
>fertility contribution versus reseeding is that a green manure will
typically
>have the highest levels of nutrients in its tissues, and the highest weight
(not
>counting seeds), when it is in the beginning of full bloom. As seeds are
formed,
>nutrients pass from the plant to its seeds, which are, as a result,
excellent
>concentrated sources of N, P, K, and minerals (that's why they're so good
for us
>to eat). Plants which have gone to seed are not so great as N-P-K-style
>fertilizers, though they can still make a significant carbon contribution,
>important for humus formation. Just don't let the carbon get way ahead of
the
>nitrogen if you are planning for production, as microbia will tie up the
>existing nitrogen while working on decomposing the carbon -- growing plants
>cannot compete with the efficiency of the microbia and will suffer nitrogen
>deficiency. This is why you'll see that grass growing through sawdust
mulches
>(very high C:N ratio) will have yellowed blades and poor, spindly growth. 
>
>When to cut for max fertility contribution also depends on whether plants
can be
>expected to regrow, or to die back upon cutting. Ryegrass, for instance,
will
>stand several cuttings if cut when young, but will typically die back if cut
>just as seeding begins. The single cutting at seeding will weigh more than
the
>smaller cuttings individually, but not cumulatively. Not only will several
>cuttings give a higher total dry weight (up to over 5,000/acre or 5,000
kg/ha),
>but it will also be richer in terms of nitrogen. For plants which do not
regrow
>after cutting, there is in general no advantage to cutting before flowering
>begins -- some weight gain would be lost. The grasses, in general, make
>excellent nitrogen recovery crops for following crops in a rotation, and
often
>enough N remains after cropping that the total N captured by ryegrass can
meet
>or exceed the amount which would be produced by a leguminous green manure
crop.
>This because, although the legume will have double the tissue analysis for
N,
>the ryegrass will have double the total weight -- plus the added carbon
>contribution and the capture of the other-wise wasted existing nitrogen. 
>
>Jack Rowe
>Seeds of Texas Seed Exchange
>[email-masked]