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Re: No-till , Nature, and Soil Quality

     I, too, firmly believe that conservation tillage practices can 
     contribute to improved soil quality.  And the only question i have for 
     an earthworm is: How can we minimize the rapid leaching of nitrate in 
     wormholes, especially during periods of low crop N demand?  
     
     I have tried to keep up on the advantages of increasing earthworm 
     populations and recently had the opportunity to ask Clive Edwards 
     about the nitrogen issue.  If i understood him correctly, earthworm 
     burrows are great for most everything EXCEPT minimizing nitrate 
     leaching.
     
     Working in the nutrient sensitive Tar Pamlico River Basin in North 
     Carolina, one of our major goals is to reduce nitrogen load to the 
     basin and its associated estuaries.  In Upper Coastal Plain and 
     Piedmont environments, we record a reduced nitrogen load due to a 
     reduction in soil loss which may be associated with increased 
     infiltration.  The increased infiltration, especially under mulches, 
     can result in greater amounts of soil water available to the plant.  
     Better moisture conditions during the growing season can, in turn, 
     result in better nitrogen use efficiencies - and reducing the 
     potential for leaching through the earthworm holes in the winter 
     months.  The impact of earthworm burrows is outweighed by better 
     growing environments during the summer months.
     
     BUT, for the Lower Coastal Plain the story is different.  With soil 
     loss already low due to < 2% slopes, there is less of an impact on 
     infiltration, and based on our nutrient accounting method there is 
     little if any reduction in the nitrogen load leaving the field .  Does 
     the presence of earthworm holes allow nitrogen to reach shallow 
     groundwater more rapidly than if there were no burrows?  What are the 
     advantages of conservation tillage systems in flatlands with regard to 
     nitrogen load reductions.
     
     I hope my comments are all accurate with regard to the science of the 
     systems discussed.  And hope that some of you will have thoughtful 
     responses to the issues raised.
     
     cheerio,
     noah ranells
     tar pamlico basin coordinator
     nc division of soil and water conservation
     


______________________________ Reply Separator _________________________________
Subject: No-till , Nature, and Soil Quality
Author:  Raymond Weil <rw17@umail.umd.edu> at Internet
Date:    4/22/97 11:13 AM


Dear Sanetters,

I know that no-till technology presents a dilema to some in sustainable
agriculture, particularily those greatly concerned about reducing, if not
eliminating,  pesticides for organic certification or other reasons.   There
is no question, however,  that GOOD no-till management (no-till, like so
many other systems, is often abused and distorted), which should almost
always include cover crops, crop rotation, and animal integration,  works
wonders for soil quality and erosion reduction. One need only consider the
example of Nature to see that tillage is probably the most disruptive and
foreign practice possible in soil management. Here in East, the model of
Nature is the forest floor, a soil system that good no-till management will
begin to mimick after  5 or 6 years.  Doing this completely without
herbicides is a tremendous challenge, one that  our research has only
partially accomplished. Until that goal is realized, I truely believe that
the trade-off between the possible ecosystem disruption of careful herbicide
use and the certain, major  disruption of tillage is positive one. Ask any
earthworm!


To the Health of Your Soil!


Ray R. Weil
Professor of Soil Science
Dept. of Natural Resource Sciences & LA
1103 H.J. Patterson Hall
University of Maryland
College Park, MD 20742
USA

telephone: 301 405 1314
FAX:            301 314 9041
e-mail:  rw17@umail.umd.edu