Date: Mon, 4 Jun 2001 09:19:02 -0700 Reply-To: amcguire@coopext.cahe.wsu.edu Sender: Sustainable Agriculture Network Discussion Group From: Andy McGuire Subject: Double Digging study In-Reply-To: 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 Comments: Authenticated sender is From: Steve Diver Subject: Re: Double Digging Comments: cc: CAVM@AOL.COM In-Reply-To: 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 Sender: Sustainable Agriculture Network Discussion Group From: Alex McGregor 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