permaculture

[Lawrence London <lfljvenaura@gmail.com>]

Studies on the double digging gardening method.
http://www.ibiblio.org/london/orgfarm/double-digging.txt

Date:         Mon, 4 Jun 2001 09:19:02 -0700
 Reply-To:     amcguire@coopext.cahe.wsu.edu
 Sender:       Sustainable Agriculture Network Discussion Group
               <SANET-MG@LISTS.IFAS.UFL.EDU>
 From:         Andy McGuire <amcguire@COOPEXT.CAHE.WSU.EDU>
 Subject:      Double Digging study
 In-Reply-To:  <aa.16510607.284b6fd8@aol.com>
 Content-Type: text/plain; charset="us-ascii"

 Here is one study that looked at double digging:

 Author(s): Holt, B.F. ; Smith, I.K.
 Title: Small-scale intensive cultivation methods: the
 effects of deep hand tillage on the productivity of bush
 beans and red beets.
 Source: American journal of alternative agriculture. 13, no.
 1 (1998): p. 29-39.
 Additional Info: Greenbelt, MD : Henry A. Wallace Institute
 for Alternative Agriculture. Publishing Agencies: US
 Imprint, not USDA
 Standard No: ISSN: 0889-1893
 Language: English
 Abstract: This study examined how one aspect of intensive
 cultivation, double digging by hand (loosening the planting
 bed to 50 cm deep), contributed to crop productivity and
 nutrient uptake in bush beans (1994 and 1995) and red beets
 (1995 only). Comparison beds were prepared with the soil
 cultivated to 25 cm (single dig) and 6 cm (surface
 cultivation). Although there were significant differences
 (1994 beans) between the surface cultivated beds and other
 cultivation types for leaf mass and chlorophyll content,
 there were no significant differences in the total mass of
 beans (whole fruit) produced. There were no significant
 differences in beet green or root (edible portion) biomass
 among cultivation methods. Levels of Ca, Mg, and K in the
 bean fruits and beet roots were not significantly different
 among cultivation methods. This study demonstrated that deep
 cultivation significantly alters the soil profile as
 measured by penetrometer resistance, but that this change
 does not necessarily alter productivity or nutrient uptake.
 We suggest that deep hand tillage has little effect on crop
 productivity in well-watered and moderate to high fertility
 soils. These results are similar to those found in
 mechanically subsoiled systems.




Date:         Mon, 4 Jun 2001 12:17:52 -0600
 Reply-To:     steved@ncatark.uark.edu
 Sender:       Sustainable Agriculture Network Discussion Group
               <SANET-MG@LISTS.IFAS.UFL.EDU>
 Comments:     Authenticated sender is <steved@ncatark.uark.edu>
 From:         Steve Diver <steved@NCATARK.UARK.EDU>
 Subject:      Re: Double Digging
 Comments: cc: CAVM@AOL.COM
 In-Reply-To:  <aa.16510607.284b6fd8@aol.com>

 CAVM@AOL.COM wrote:
 > I know it is almost a sin to make assertions without cites but I can not
 > recall where I read a few weeks ago about a test done with single digging 
 > of
 > a garden and double digging.  The double digging did no better but was
 > considerably more work.

 The American Journal of Alternative Agriculture featured a paper
 in 1998 that summarized research on double digging in comparison to
 single digging.

 Holt, Ben F., and Ivan K. Smith.  1998.  Small-scale, intensive
 cultivation methods: The effects of deep hand tillage on the
 productivity of bush beans and red beets.  Am. J. Alt. Agric.
 Vol. 13, No. 1.  p. 28-39.

 Table of Contents online:
 American Journal of Alternative Agriculture
 http://www.winrock.org/wallacecenter/ajaa.htm

 Intro to Abstract:
 "This study examined how one aspect of intensive cultivation, double
 digging (loosening the planting bed to 50 cm deep), contributed to
 crop productivity and nutrient uptake in bush beans (1994 and 1995)
 and red beets (1995 only).  Comparison beds were prepared with the
 soil cultivated to 25 cm (single dig) and 6 cm (surface
 cultivation)."

 Conclusion to Abstract:
 "This study demonstrated that deep cultivation significantly alters
 the soil profile as measured by penetrometer resistance, but that
 this change does not necessarily alter productivity or nutrient
 updake.  We suggest that deep hand tillage has little effect on crop
 productivity in well-watered and moderate to high fertility soils.
 These results are similar to those found in mechanically subsoiled
 systems."

 Excerpt from Conclusion:
 "Because of the high labor and energy costs of double digging, the
 results from this study suggest that it should be avoided in
 locations with sufficient rainfall, moderate to high soil fertility,
 and no definite root-restricting soil horizons.  Because the effects
 of deep hand tillage have received little attention to date, we
 designed this study as a starting point for further research.  Plants
 were given sufficient nutrients and moisture.  The present study does
 not address plant productivity under severely limited supplies of
 nutrients or moisture, an area that clearly requires further
 investigation.  Where there are restricting horizons or resource
 limitations, the small-scale farmer might consider double digging
 once, followed by continued proper bed management."

 Some comments:

 The largest commercial biointensive farm I've encountered was a
 1 acre organic market farm in California, where the intensive
 double digging was peformed by hired Mexican labor.

 Alex McGregror's biointensive mini-farm in Tenneesse is the one
 that comes to mind as a practical example of the John Jeavon's
 biointensive model in action, modified according to fit Alex's
 ideas and resources.

 Alex gave a presentation to a room-packed audience at the Southern
 SAWG conference in January, 2001. My recollection is that he follows
 something very close to what the conclusion to the AJAA article above
 said, "the small-scale farmer might consider double digging once,
 followed by continued proper bed management"; i.e., he double digs
 the first year only.

 Incidentally, Timberleaf Soil Testing Lab in California offers a soil
 test that is specifically geared to biointensive market farming.
 This soil test grew out of Steve Rioch's program at Ohio State
 University.

 Steve Diver


Date:         Tue, 5 Jun 2001 09:27:57 -0400
 Reply-To:     Sustainable Agriculture Network Discussion Group
               <SANET-MG@LISTS.IFAS.UFL.EDU>
 Sender:       Sustainable Agriculture Network Discussion Group
               <SANET-MG@LISTS.IFAS.UFL.EDU>
 From:         Alex McGregor <waldenfarm@SPRINTMAIL.COM>
 Organization: Walden Farm
 Subject:      Re: Double Digging
 Content-Type: text/plain; charset=us-ascii

 Steve & Andy,

 Thanks for pointing out the reference.  This is the only scientific research 
I
 know of about "double digging."  I would like to point out a few
things about this
 paper.

 1. These comparisons were done using beans and beets- selected by Ben
and Ivan to
 represent fruit and root crops.  The flaw here is that both these do
not require
 peak fertility to produce a crop.  This was pointed out to me (and
Ben) by Steve
 Rioch.  Steve suggested they use carrots as the root crop and a
non-legume for the
 fruit; that is, a high nutrient & high fertility demanding plant.

 2.  Please note in the conclusion the part about high fertility and adequate
 moisture.  Jeavons' work started in soil that had been graded below the 
subsoil
 level and in an area of California with low rainfall.  He developed
his techniques
 to match these.  My point is that no type of agriculture should be
considered an
 orthodox religion.  It needs to be applied to match soil, climate, crops and
 resources.

 3. Ben didn't use Steve as a resource for this study.  He had had a falling 
out
 with Steve and changed his Master's program from Biointensive to
Botany.  I taught
 the Garden portion of Steve and Ivan's classes during these years and
talked with
 Ben about his research.  I found him to be an angry young man who had 
concluded
 that "Biointensive doesn't work" before the research was concluded.

 Alex McGregor
 Walden Farm