Date: Wed, 2 May 2001 20:24:21 -0600 Reply-To: steved@ncatark.uark.edu Sender: Sustainable Agriculture Network Discussion Group Comments: Authenticated sender is From: Steve Diver Subject: Strawberry's, Methyl Bromide, Compost, Mycorrhizae Strawberry Fields (Forever), Methyl Bromide, Compost, Mycorrhizal Inoculation, Rhizosphere, Frank Sances, Elaine Ingham, Soil Foodweb SANET Readers - In the thread on Effective Microorganisms (EM), Alex McGregor and Dale Wilson referred to the strawberry work in California by Elaine Ingham. This is the work that Frank Sances and Elaine Ingham conducted in the Santa Maria Valley, looking at alternatives to methyl bromide through soil health-building practices. "Crop Profile for Strawberries in California" on the USDA OPMP/PIAP web page contains an authoritative summary of strawberry production in California, with: total acreage; specialized regions of production; amazing facts on the volume of nursery plants grown and used; and common pests and control options. Crop Profile for Strawberries in California http://pestdata.ncsu.edu/cropprofiles/docs/castrawberries.html The aforementioned Sances-Ingham strawberry trials have been conducted annually since 1994. Treatments have included a series of organic amendments and microbial inoculants with the intention of re-establishing a healthy soil foodweb as a biocontrol mechanism for soil-borne pathogens. In other words, instead of using soil fumigants like methyl bromide to control the disease complex that severely reduces strawberry yields, the idea was to add organic residues and composts to the soil to support a functional soil foodweb to fight these soil-borne pathogens through natural biological control. Interestingly, the disease complex that harms strawberry roots and reduces yields is a direct result of human activity. Farmers -- in the early part of the century through repeated plowing and application of raw manures, and then later using a smorgasborg of NPK fertilizers and synthetic pesticides -- impacted the natural health of soils in the rich agricultural valleys of California. Dr. Ingham refers to a book, "How Bountiful the Soil" that talks about valley conditions at the turn of the century. Some of these California soils contained 10-15% organic matter. Crops where healthy, with few insect or disease problems. However, within 15 years of the beginning of annual cropping and plowing, fertility started dropping and yields declined. This is when applications of raw manures were initiated to provide nitrogen and organic matter. Despite the addition of manures, repeated plowing spurred the depletion of organic matter which reduced total numbers and diversity of microbial populations. And while raw manures add raw organic matter and nutrients to the soil, they can also result in high levels of nitrates and pockets of anaerobic conditions which in turn results in toxic byproducts. Under these conditions, pathogenic organisms like fusarium started to flourish. By 1955, fungal diseases were out of control; methyl bromide arrives on the market as a soil fumigant. By 1975, methyl bromide is applied every 2 years. By 1985, methyl bromide is applied before every crop Working in conjunction with Frank Sances of Pacific Ag Research, Elaine Ingham conducted a microbial assy of Santa Maria Valley in the early 1990s. This is what she found: *Microarthropods, all gone *Protozoa, all gone; Thus, nutrient cycling capability also gone *Fungal hyphae, all gone *Bacteria, 100 species per gram; Thus, no nitrogen retention, no disease suppression *Root-feeding nematodes present: sting, citrus, root knot, etc. *Spore-forming pathogenic fungi present: Pythium, Rhizoctonia, Phytopthera *Santa Maria river, at certain times running at 150 ppm Nitrates *EPA drinking water maximum for Nitrates, 10 ppm In contrast, some characteristics of a Healthy Soil include: 600 million bacterial individuals, 15,000 to 20,000 species per gram 150 meters fungal biomass, 5,000 to 10,000 species per gram 10,000 protozoa 20-30 nematodes, Bacterial-Feeding, Fungal-Feeding, Predatory 200,000 arthropods per square meter At some point -- I presume in the early 1990s -- Frank Sances and Elaine Ingham found each and hooked up to look at organic amendment treatments as an alternative to methyl bromide. Early-on, treatments included broccoli residues and spent mushroom compost. A number of research reports in the 1980s showed that cruciferous plants contain fumitoxic compounds such as glucosinolates and isothiocyanates, spurring the use of cover crops like oilseed radish, mustard, and rapeseed in an attempt to control plant-feeding nematodes and soil-borne diseases. So applying broccoli residues hauled from nearby broccoli fields in the valley seemed like a reasonable idea, as a natural fumigant for strawberry beds. However, early research results showed that neither of these organic amendments worked very well. The high levels of broccoli residues didn't match the goals of a soil foodweb transition (too much fumitoxic sulfur? bacterial food source rather than fungal food?, I'm not quite sure), and secondly, the spent mushroom compost was more akin to a lower-grade compost useful as a mulch rather than a high quality compost geared to disease suppression. In the following year(s), Sances-Ingham shifted to a premium grade compost as a soil treatment, and started working with strawberry plants raised in plugs (as opposed to the standard practice of bare root plants). Special attention also turned to the plug potting mix itself, specifically augmenting the mix with a premium-grade compost and a mycorrhizal inoculant. All of these soil-health-building practices and organic amendments treatments were compared to soil fumigants, and a control. There is a good reason to pay attention to this work. For one, organic strawberry production was hardly done until recent years. The whole agricultural industry was so heavily biased towards chemical inputs that nobody dared think that it could even be done. In commercial strawberry production, soil fumigants like methyl bromide are commonly used as biocides to kill soil life. It sets back the disease complex that hinders strawberry production long enough for a crop to grow and yield a bountiful harvest. Herbicides are used to control weeds. NPK fertlizers are used to provide fertility. Fungicides and insecticides are used to control bugs and diseases. Plastic mulches are used in combination with drip irrigation. Soluble NPK fertilizers are injected through the drip lines. From the ag industry viewpoint, all this just seems like an acceptable way to produce a crop and make money. The cost of strawberry production in California -- largely driven by astronomical land prices -- is enormous. Thus, farmers have a very distinct need for *confidence* that a crop will produce good yields, and the methyl bromide plasticulture strawberry production system works very well from a farmer's viewpoint and from a banker's viewpoint. From the sustainable agriculture viewpoint, however, it simply does not make sense to kill soil life and treat the soil like a hydroponic medium rather than work with soil life and work within the constraints and principles of nature. Likewise, it is alarming to see farmland soils treated with biocides like this year-after-year for so long, and it is also raises questions about food quality and food safety of the actual berry crop. A foremost concern of chemically-intensive strawberry production, is the health and safety of farmworkers who treat the fields with products like methyl bromide and pesticides. There is also the concern of nearby neighbors, including schoold children and teachers. SANET has listed a few reports over the past years regarding pesticide residue concerns on strawberries, and about fumigation taking place in close proximity to schools, so this information is not new. In addition, agricultural runoff of fertilizers and pesticides is a concern. The most glaring example of this problem is the hypoxia problem in the Gulf of Mexico; largely due to agricultural runoff from two-thirds of the United States watershed. Based on the nitrate levels detected during certain periods in the Santa Maria River, it seems this can be a significant problem in California, too. OK, recognizing there is a concern about the standard chemical-strawberry production approach, what are some positive things to look to? Two trends emerge: One is the phase-out of methyl bromide. Methyl bromide is an ozone depleter and according to EPA guidelines it must be removed from the market by 2006, with declining total usage each year until it has reached 100% phase-out. The EPA Methyl Bromide Phase Out web site contains all the essential information on this topic. U.S. EPA Methyl Bromide Phase Out Web Site http://www.epa.gov/ozone/mbr/mbrqa.html A positive result from the fast-paced research undertaken to find alternatives to methyl bromide is that cultural and biological practices have gained as much attention as chemical alternatives to methyl bromide. Secondly, organic farming methods for strawberries and other crops have made significant advances in recent years. Good markets for organic produce have prompted large California farms to try their hand at this production system, conceptual thinking and concrete knowledge as to how to approach organic farming systems have expanded exponentially since the late 1980s, and organic input products and equipment technologies have been developed to meet the challenge. As a consequence, some interesting research and field results have taken place. In addition to the Sances-Ingham plots, some of the research grant programs that have propelled field trials on organic farming methods as well as methyl bromide alternatives include the USDA-SARE program and UC-SAREP in California. The following SARE & SAREP databases, as well as the USDA TEKTRAN database, can be searched to find research results using keywords like: strawberry, organic, rhizosphere, compost, mycorrhizae, biocontrol: SARE Research Projects Database http://www.sare.org/san/projects/search.html UC-SAREP Funded Projects Database http://www.sarep.ucdavis.edu/grants/database/ Selected Publications Resulting from SAREP Grants http://www.sarep.ucdavis.edu/grants/SelectedPubs.html TEKTRAN - Technology Transfer Automated Retrieval System http://www.nal.usda.gov/ttic/tektran/tektran.html So what are the results from the Sances-Ingham plots? ============================================= Dale Wilson wrote: I found two references (attached below) in Biological Abstracts apparently from this work. Here are a few of the conclusions from the one hit that contained an abstract: - "Weeding costs were five-fold greater in organic treatments" - "Strawberry yields were highest in the methyl bromide/chloropicrin, Basamid and Telone/chloropicrin treatments." - "Strawberry yields among the organic treatments were not statistically different from the untreated control." - "single application of these particular organic amendments were inadequate in significantly increasing soil food web diversity." References: TI: Conventional and organic alternatives to methyl bromide on California strawberries. AU: Sances-Frank-V {a}; Ingham-Elaine-R SO: Compost-Science-and-Utilization. 1997; 5 (2) 23-37. ============================================= Based on this citation alone, the results don't look too good. But this citation is one glimpse at a multi-year study. Before I list the research reports, let me return to the Sances-Ingham plots and provide further insight. Strawberry plants are obligately mycorrhizal plants. In her research on the soil foodweb -- combined with the accumulated knowledge of soil microbial ecology studies -- Dr. Elaine Ingham found that row crop plants (grasses, annual row crops, vegetables) like to inhabit or create a bacterially-dominated soil ecoystem, while woody plants (trees, shrubs, vineyards) like to inhabit a fungal-dominated soil environment. Strawberry plants are understory woodland plants. Thus, in their natural habitat they live in a fungal dominated environment, in the forest. Linking these ideas with treatments, Sances and Ingham started amending the potting mixes for strawberry plugs with high quality composts and a mycorrhizal inoculant. If the soil foodweb of the strawberry plant root system can be shifted to the strawberry plant's liking -- especially boosting the rhizosphere -- then perhaps the organic plots will promote a functional and diverse soil foodweb to ward off the pathogenic organisms which result in the disease complex necessitating the use of methyl bromide in the first place. Results, as reported previously on SANET (see below): In California, as well as in North Carolina, amending the strawberry plug potting mix with a good quality compost and mycorrhizal inoculants resulted in yields comparable or superior to methyl bromide plots. The North Carolina study: Alternatives to Methyl Bromide Fumigation in North Carolina's Annual Strawberry Production Systems. M.A. Grabowski, F.J. Louws, and G.E.Fernandez. Plant Pathology, North Carolina State University 1999 MS Symposium Abstracts http://www.cals.ncsu.edu/plantpath/Graduate/msabstr99.htm According to notes from Elaine Ingham's soil foodweb seminar, February 2001, strawberry yield increases in the organic plug plant plots over the methyl bromide plots follow a curve that looks like this: Year 1: 600 lbs more Year 2: 1,000 lbs more Year 3: 1,200 lbs more Year 4: 1,500 lbs more The principle here is worth repeating over and over again: Feeding the soil with organic amendments and/or creating a diverse crop mix above ground helps create an Abundance and Diversity of soil organisms. This Abundance and Diversity of soil organisms is so important. It is the backbone of organic agriculture, supported through decades of research, experience, and observation. Compost, cover crops, crop rotations, intercropping, agroforestry, mulch, manures, compost teas... all of these practices support and enhance the Abundance and Diversity of soil life, and that is why I emphasize this principle in my seminars and tell farmers and gardeners that they can throw NPK fertilizers out the garage door if they pay attention to this fundamental concept. [And anytime you can bring along a dissecting microscope and a bag of decomposing organic matter full of wiggly compost creatures, the soil life principle sinks in pretty fast.] When healthy, functional soil life is in place, productive crop yields can be achieved with zero dependance or greatly reduced dependance on fertilizer and pesticide inputs. Of course, slow-release mineral fertilizer supplements like rock minerals or rock dusts and lime are common soil amendments that support the biology, chemistry, and physics of soils in the context of organic farming systems and that's another part of the soil health picture that should not be neglected. But it is soil biology, the vast number of species, the immense total numbers of these creatures, that controls and regulates nutrient cycling, organic matter decomposition, humus formation, and related biochemical activities, including the ability of a soil to be naturally suppressive to diseases. So that is some background information to this story. Whereas methyl bromide is used by commercial farmers because it provides confidence in the production of a successful strawberry crop, in contrast I feel the preceding story is important because it can provide a similar level of *confidence* that organic strawberry production is feasible when attention is paid to a healthy soil foodweb. Likewise, it supports the view that augmenting the crop at each point of the organic production cycle can be important; for example, supplementing the plug mix, amending the planting bed, foliar feeding with compost teas, etc. In the web links below I have included previous SANET posts on this general topic. These include the USDA Methyl Bromide Alternatives website which contains numerous studies and reports on cultural and biological practices, as well as additional details on the Sances-Ingham strawberry research. Next, the EPA website contains full text proceedings of the Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions. Papers from Frank Sances detailing the strawberry research can be found for 1995, 1997, 1998, 1999, and 2000. Though it appears that the PDF versions of these papers are missing some of the graphical charts displaying yield data. For reasons unknown, the 1996 proceedings are absent from the website. These proceedings also contain reports from dozens of researchers looking at a host of cultural and biological alternatives, and many of these are quite revealing for the insight they provide in support of sustainable agriculture. This whole post is a mouthful but I hope it helps paint a clearer picture of soil foodweb practices that offer an option for organic strawberry production, and how farmers can adapt alternatives to soil fumigation which is not very safe for farmworkers, the environment, or the living soil. Steve Diver ATTRA http://www.attra.org ========================================= SANET web archives with related material on this thread: Alternatives to Methyl Bromide Yields Benefits to Farmers Sat, 4 Oct 1997 00:51:38 +0000 SANET Web Archives http://www.sare.org/htdocs/hypermail/html%2Dhome/21%2Dhtml/0367.html Re: Compost, Mycorrhize Alternative to Methyl Bromide in Strawberry Date: Fri Mar 31 2000 - 16:24:32 EST SANET Web Archives http://www.sare.org/htdocs/hypermail/html%2Dhome/43%2Dhtml/0420.html Strawberry + mycorrhizae + compost = NO methyl bromide Date: Fri, 24 Nov 2000 20:32:40 -0600 SANET Web Archives http://lists.ifas.ufl.edu/cgi-bin/wa.exe?A2=ind0011&L=SANET-MG&P=R4221 1 Note: You may have to copy and paste one or two characters from this web address onto your web browser to get this last web link on the SANET web archives to work. ===================================================== ===================================================== Online Proceedings of the Methyl Bromide Alternatives and Emissions Reductions conferences From: 1995 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions http://www.epa.gov/ozone/mbr/mbrpro95.html Suitability of Organic Compost and Broccoli Mulch Soil Treatments for Commercial Strawberry Production on the California Central Coast (F.V.Sances and E.L. Ingham). http://www.epa.gov/ozone/mbr/1995airc/019.pdf From: 1997 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions http://www.epa.gov/ozone/mbr/mbrpro97.html Conventinonal and Organic Alternative to Methyl Bromide On California Strawberries (Frank V. Sances) http://www.epa.gov/ozone/mbr/1997airc/037sances.pdf From: 1998 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions http://www.epa.gov/ozone/mbr/mbrpro98.html Conventional and organic alternatives to methyl bromide on California strawberries (Frank V. Sances and Elaine R. Ingham). http://www.epa.gov/ozone/mbr/1998airc/023sances.pdf From: 1999 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions http://www.epa.gov/ozone/mbr/mbrpro99.html Conventional and Organic Alternatives to Methyl Bromide on California Strawberries (Sances) http://www.epa.gov/ozone/mbr/1999airc/9sancesf.pdf From: 2000 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions http://www.epa.gov/ozone/mbr/mbrpro00.html Conventional and organic alternatives to methyl bromide on California strawberries. Frank V. Sances Ph.D. Pacific Ag Group, San Luis Obispo, California http://www.epa.gov/ozone/mbr/altmet00/24sances.pdf