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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