permaculture

["Lawrence F. London, Jr." <venaurafarm@bellsouth.net>]

-------- Original Message --------
Subject: [SANET-MG] Soil organic matter
Date: Sun, 2 Jan 2011 00:24:59 -0800
From: Mary-Howell & Klaas Martens <kandmhfarm@SPRINTMAIL.COM>
To: SANET-MG@LISTS.IFAS.UFL.EDU

That was a great post Karl and thank you Joel for the links and references
you posted earlier.

I think that Karl's post shows us that all farming is local.  While there
are universal general principles that apply to all agriculture, farmers
everywhere must adapt their practices according to local conditions.  The
Cubans may be fortunate to have developed their system of farming without
the 'help' of outside experts.

I remember reading Sir Albert Howard's account of going to India with all
the knowledge and arrogance that the best agricultural schools in the world
(England's) could give him and then meeting who he called his 'real
professors' of agriculture: the peasant farmers who had lived there for many
generations.  He recounted how he introduced the northern European practice
of plowing in a legume cover crop to improve the soil and that it seldom
produced the same positive results in India that it had in England.  He also
observed that the years when it did work were also the years when the
monsoon rains failed or were very light.

> From that he figured out that during the long periods of warm
> anaerobic soil
conditions that occurred in the monsoon season in India, the fresh organic
matter was broken down and lost before it could benefit the next crop.  He
had previously regarded the labor intensive practice of gathering all the
crop residues manure and other materials from the fields and putting them
into aerobic compost piles during the monsoons as a waste of labor.

We are lucky that Sir Albert was humble enough and smart enough to learn
from his observations and apply them on his own farm.  He passed that
knowledge on to later generations.

Some of the least productive soils I've ever worked with are old meadows and
hayfields in the low hills of eastern New York.  They are very high in
organic matter.  Some of them have OM levels as high as 8% yet they produce
very low crop yields.

High organic matter does not guarantee good crops.  It is in the breakdown
of organic matter that fertility is released for subsequent crops to use.

Building organic matter alone is not best goal for managing soil.  Just
storing OM without using any of it will result in very poor crop yields.  As
soluble minerals are tied up by crop growth, the soil becomes progressively
poorer and yields decrease.

Productive soil needs to have actively cycling organic matter.  Simply
reducing the rate of organic matter decay does not necessarily result in
better soil.  It just slows down its biological activity.  Healthy
productive soil needs to have a high rate of biological activity.  That
means a high rate of organic matter breakdown.  As long as more organic
matter is added to the soil each year than what is consumed, the soil gains
organic matter content.

Long term No-till farming does not raise total soil organic matter unless it
includes cover crops.  Even with cover crops, it does not always improve
organic matter.  It often only increases the OM levels near the surface
while depleting OM levels deeper in the soil profile.

I've observed some large increases in SOM in soils that are moldbord plowed
regularly.  These statements aren't opinions.  They are direct observations.

I had a SARE grant several years ago that included testing soil every 6
weeks.  We were surprised to see organic matter levels increase through the
spring and summer after the land was plowed and peak in about August -
September.  That was without us making any outside additions of OM.  In 1999
it increased by a full percentage point between June and late August across
six fields in different stages of rotation.

If plowing destroys organic matter, why did it increase so much after spring
tillage?  The biggest single drop in OM we observed throughout the
experiment, was after a very heavy period of rain that left the soil
waterlogged for many weeks.

Klaas