EARTH WORMS and RESIDUE

   
     It is becoming more common to see articles and presentations referencing the presence of earth worms as an indicator of soil health.  Does that mean you have reached the goal of returning the ground back to it's original self sustaining condition that was present prior to man's intervention?  NO, --it is one of many indicators!  The compaction layers, low pH, low SOM, and high erosion can be present and still have a significant population of earth worms, both horizontal movers and vertical movers.  I'm not convinced that every acre of ground has a native population of earth worms, --they either were never there, or conditions became so bad over time that they disappeared.  I am convinced that earth worms will move into an area if conditions change that will allow them to survive.  I have always been able to find earth worms in the early spring in the low areas where moisture was plentiful, even prior to no-tilling, --just not very many.  I soon learned as a kid that it took a lot of spading in the crop ground to find enough worms for a day of fishing, where, if I went to an area that had a lot of residue and was pretty wet, it only took a few spade full of dirt to fill my needs.
       What will encourage earth worms to inhabit cropped fields?  They need food, and shelter just like any other living thing.  If their homes and food are not destroyed on a regular basis they will be there or move there.
       The recent No-Till Farmer magazine had an insert titled "12 UNRIVALED BENEFITS OF EARTHWORM ACTIVITY IN YOUR SOILS".  When I first read them, several seemed to be repetitive, but they were different, but had similarities.  These 12 points come from various university studies throughout the US.  I'm going to paraphrase a two page article to shorten this post.  1--Improve Water infiltration:  Pencil thin burrows allow rainwater to penetrate deep into and throughout the soil profile.  2--Improve Soil Aeration:  Burrows are conduits for air moving into the soil profile and CO2 movement out to stimulate plant growth.  3--Increased Hardpan Penetration:  Earthworm tunnels once bored through the hardpans stay and improve root access.  4--Reduced Soil Compaction:  Burrows both vertical and horizontal encourage root growth, which helps breakup compacted areas.  5--Mix Surface Residue Into Soil:  Some species pull residue into the soil.  63000 worms per acre will make about 18 tons of castings.  In ten years they are capable of complete renewal of 2" of topsoil.  6--Release Of Crop Growth Stimulants:  Earthworms break down crop growth inhibitors, phenols and formaldehyde from decaying residue and lace the material with growth stimulants, auxins and cytokinins.  7--Bring Minerals Up From Subsoil:  Earthworm castings contain 5-10 times the soluble plant nutrients of the original soil.  8--Neutralization of Soil PH:  Earthworm processed soil is always closer to neutral pH.  9--Rapid Growth Of Beneficial Microbes:  Earthworms carry around and deposit beneficial microbes as they go.  These thrive and help decompose residue.  10-- Improve Soil Tilth:  Earthworm castings contain sugars and enzymes which help build soil aggregates.  Fields bulk up being more sponge like.   Fields with high worm populations have 4 times infiltration rate of fields without earthworms.  11-Improved Nematode Control:  Earthworms eat harmful nematodes and leave  soil conditions that limit nematode numbers.  12-- Increase Micronutrient Chelation:  Earthworms link micronutrients, such as zinc and boron to other nutrients for easier uptake by plant roots.  13--Reduce Erosion:  I'll add this one to the list.  The surface residue required for the listed benefits above, along with the earthworm tunneling to the surface slows water loss, hence, reduces erosion.
      Earth worms are truly natures plows, only they do a much better job by leaving a less erosive soil, cycling minerals through the soil, and improving moisture infiltration.  The higher the population the better.  Earth worms are a great indicator of which direction your soil is headed, --to a healthier state or to DIRT.
      The Take Home Message Here Is:  DON'T TILL AND DON'T REMOVE RESIDUE!