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  • From: "Tradingpost" <tradingpost@lobo.net>
  • To: livingontheland@lists.ibiblio.org
  • Subject: [Livingontheland] Soil Fertility Basics: Organic Matter by Steve Peters
  • Date: Fri, 18 Jul 2008 13:04:51 -0600


Soil Fertility Basics: Organic Matter by Steve Peters
http://www.seedsofchange.com/enewsletter/issue_20/issue_20.asp


The key to growing healthy, nutritious plants is maintaining fertile soil.
Much more than dirt, garden soil is a richly complex ecosystem that is as
dynamic and diverse as a tropical rainforest. Most soil activity, however, is
invisible to the human eye so we tend to think of soil as merely a medium for
holding up plants. Nothing could be further from the truth. A single gram of
soil can host billions of living organisms!

Soil The most important component for sustaining a healthy, living soil is
organic matter (OM). OM comprises all organic substances in varying stages of
decay including plant roots, stems, and leaves, microorganisms, and added
organic materials such as compost, manure, and straw. When organic matter
reaches its most mature and stable form it is called humus, a dark and
fragrant, nutrient rich substance essential for long term soil fertility. OM,
and in particular humus, serves many vital purposes. It attracts and holds
essential plant nutrients. It acts much like a sponge by retaining moisture.
It produces vitamins, hormones, and other growth substances important for
plant health. It is also critical for maintaining good soil structure by
binding the mineral portion of the soil into loose aggregates. This permits
air to reach the roots, allows for capillary movement of water, and enables
roots to penetrate the soil.

Finally, and perhaps most significantly, organic matter is the food source
for soil based organisms, including bacteria, fungi, actinomycetes, yeasts,
soil-dwelling insects and earthworms. Without these living organisms plants
would cease to exist. They perform a variety of critical processes including:
1) Converting organic nitrogen, which is unusable to plants, into inorganic
nitrogen compounds (ammonia and nitrates) which are available to plants; 2)
fixing atmospheric nitrogen and making it available to plants; 3) producing
organic acids that make mineral nutrients soluble and available to plants; 4)
living symbiotically on plant roots and aiding the plant in the uptake of
many important nutrients and growth substances; 5) preying on pathogenic
organisms that would otherwise be detrimental; 6) contributing to soil
aggregation by producing gum-like polysaccharides; and 7) producing carbon
dioxide (CO2) which is released into the atmosphere and is essential for
photosynthesis.

As a home gardener, the best way to increase the organic matter content of
your soil is to add mature, high quality compost. Composting is that
seemingly magical process that transforms raw organic residues into a stable,
sweet-smelling earthy substance that contains a balanced blend of all the
essential plant nutrients. Compost can be applied to the soil at almost any
rate without fear of toxicity or loss of nutrients, although more frequent,
smaller applications are preferred. Compost provides a slow and steady
release of nutrients throughout the growing season, and can cure a variety of
problems including high or low pH or a nutrient imbalance. Mature compost is
particularly important in sandy soils which lack the ability to retain much
water or nutrients.

Another important source of organic matter is >cover crops, which are grown
specifically for soil improvement and are incorporated into the soil prior to
growing vegetables and other garden plants. Cover crops can be grown any time
of the year. Spring annuals (Oats and Triticale) are planted as soon as the
soil can be worked in early spring. Summer annuals (Buckwheat, Cowpea,
Sorghum) are grown only during frost-free months, while winter annuals
(Austrian Winter Pea, Hairy Vetch, Winter Rye) are planted in late
summer/early fall, overwinter, and resume growing the following spring. For
longer term soil-building, biennials (Yellow Blossom Sweetclover) and
perennials (Red Clover) can be grown. Cover crops are not as effective as
compost for building humus, but they stimulate a greater amount of biological
activity. In heavy clay soils, fresh cover crop residues may be preferred
over compost because they help open up the soil and provide drainage.

Raw animal manures are not generally recommended for direct application to
the garden because much of the nutrients are lost by leaching. They can also
introduce unwanted weed seeds and pathogens, and can cause over-stimulated
leafy growth because of excess available nitrogen. We recommend composting
raw manures before putting them in the garden.

Steve PetersMany organic residues such as straw, leaves, and sawdust, are
very high in carbon (C) relative to nitrogen (N). When incorporated into the
soil, these materials will stimulate biological activity. The problem is,
however, that because of a lack of N, the soil microorganisms tie up most of
the available soil N, causing a nitrogen deficiency in plants. Eventually
these microorganisms will die and release their N, but this could take weeks
or months. Therefore, it is best not to incorporate these high-carbon
residues into the soil but rather to use them in pathways, spread them as
surface mulches, or to add them to your compost piles.

There are soil tests available through many cooperative extension services
and private soil testing laboratories, which can give you an idea of the
organic matter content of your soil. However, this is often not cost
effective for the home gardener. A simple way to measure the biological
activity in your soil is to measure CO2 respiration, which is associated with
the breakdown of organic matter by soil microorganisms. Higher levels of
biological activity in the soil reflect healthier soils, which provide
essential plant nutrients like nitrogen and phosphorous. The Woods End
Institute, a leading soil and compost quality laboratory, has developed a
simple method for the home gardener to test for CO2 respiration in soil and
compost. Please look for the Solvita Garden Care Test in our product
offerings below.





  • [Livingontheland] Soil Fertility Basics: Organic Matter by Steve Peters, Tradingpost, 07/18/2008

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