Friday, September 7, 2012

"Mother Earth's Intestines"

     Yesterday we got a heavy rain that led to some urban flooding.  This was actually a very welcome event for our area as it has been locally very dry and the trees were beginning to wilt.  I am always amazed when I walk past people's yards after a heavy rain like that.  Some people have tons of earthworms that suddenly emerge seemingly out of nowhere.  Others do not have a single one.  This may not be something that you normally look for, but I see it as a sign of the health of the soil for each individual site.
     A healthy soil is teaming with organisms.  Among the most prevalent and obvious are earthworms.  These blind miracle workers are literally what my Dad used to call "Mother Earth's Intestines".  They are more digestion system that they are anything else.
     Earthworms are essential for a healthy soil.  First of all, they hugely act to reduce the amount of organic litter on a site.  A worm can literally consume half its own weight each day.  That means that all those leaves, blades of cut grass, dead insects and whatever other organic stuff ends up on the soil  can be eaten and removed by worms as food.  In the process, the worms remove this stuff from the surface and carry it underground.  There they grind it up and digest it.  Eventually the undigested matter is deposited into the soil as worm castings which act to greatly enrich the soil for plant growth.
     Worms also move through the soil.  When they do, they create tiny tunnels which are reinforced by a slimy mucus that they use to aid in their forward motion.  These tunnels are hugely important to a healthy soil in that they allow for both air and water to move into the soil.  This is a much more effective method of aeration of a planted soil than by physically, mechanically aerating it.
     Without worms, we would have massive amounts of organic matter piling up and hard, infertile soil that provides a poor host for plants.  So, they should be welcomed and encouraged.  Worms are actually quite prevalent - poor soil may have as many as 250,000 earthworms / acre but a rich fertile soil may have up to 1,750,000 / acre.  That's a lot of little creatures all working to make your site better by making your soil better.
     So why do I look for worm numbers after a rain?  There are a number of theories for why they come to the surface.  One theory is that they are surfacing because the soil is saturated and no longer has enough oxygen for them to breath.  Another theory is that they are using the wet surface conditions to move more quickly to another location than they could have had they stayed underground.  Yet another has to do with the carbon dioxide from all the soil organisms dissolving in the rainwater to create carbonic acid which irritates the worms.  Regardless of why they come up, their presence is a good indicator of soil health.
     The more worms the better!  They keep their numbers in check depending on the amount of space and organic matter available.  A site that has lots of worms most probably has good numbers of other soil organisms as well and therefore good fertility and aeration.  It also probably has good rainwater infiltration.
     What about those sites with few or no worms?  They might have been killed off by insecticides or their numbers might have declined because of a lack of organic matter or a poor, hard, dry soil.
     So, go out and look for worms.  If you don't see any, you might try encouraging them with a nice meal of grass cuttings and shredded leaves.  They love compost and will reward you with great soil.

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