The following article is a description of one of our 2010 research projects, which is being funded in part by the Nova Scotia Dept. of Agriculture.
Project title: Potential economic and agronomic benefits of the cultivation of the Almond Mushroom, Agaricus subrufescens, in tomato crop field tunnels as part of a crop rotation.
Farm owners:
Cindy Rubinfine and David Blanchard
Pleasant Hill Farm
5104 Hwy 208
Pleasant River, NS
B0T 1X0
Project leader:
Andy Radin
231 Boutiliers Point Rd.
Boutiliers Point, NS
B3Z 1S9
Project Cooperator:
Kevin Wentzell
Lunenburg Regional Recycling and Composting Facility
908 Mullock Rd.
Whynott Settlement, NS
B4V 2W2
September 10, 2009
Comprehensive project description
This project will begin in the late winter of 2010 and continue until early 2012.
The applicants intend to explore the following objectives over a two year period beginning in winter of 2010 and continuing until winter of 2012:
A. Establish effective inoculation and cultivation protocols for Agaricus subrufescens, the Almond Mushroom
B. Document effects of A. subrufescens cultivation on soil by evaluation of changes in soil nutrient and organic matter contents, and soil chemical and physical properties
C. Document mushroom tissue nutrient analysis in relation to soil nutrient status
D. Evaluate performance of subsequent vegetable crop following mushroom crop
E. Determine the feasibility of concurrent intercropping with tomato and mushroom
F. Determine overwintering ability of A. subrufescens greenhouse beds
G. Develop a farmer-friendly method of spawn production
We feel that our project is relevant to the program objectives of Innovation Fund. On-farm profitability is addressed through usage of existing infrastructure (greenhouse) and cultivated space during alternate years for production of a novel, highly marketable, and high market value crop, the Almond Mushroom (or Almond Portobello). The potential for field tunnel soil improvement from mushroom cultivation can enhance alternate year vegetable crop productivity. Use of a non-plant kingdom rotation crop can disrupt vegetable crop disease and insect pest cycles, and suppress weeds. Development of a local spawn production protocol creates potential for a new local mushroom industry.
Introduction
Cultivation of summer vegetables in Atlantic Canada is carried out successfully in many regions, but more and more growers are turning to field tunnel production for additional heat accumulation and season length. The proprietors of Pleasant Hill Farm, a certified organic, Nova Scotia-registered farm are in their third year of vegetable production at their Pleasant River, NS, location where they specialize in field tunnel-grown tomatoes. The field tunnel differs from the typical greenhouse in that crops are grown directly in the field soil, rather than in containers of medium or in hydroponic troughs. (The word “greenhouse” will mainly be used throughout this proposal, but it is to be understood that all plantings are established in field soil.) This is compatible with the philosophy of organic production, in which a top priority is the building of soil fertility and structure through the addition of organic materials in order to maintain a high level of soil biological activity. This in turn facilitates mineralization of plant nutrients at a biological pace. However, intensive production on the same small area makes great demands on the soil. Repeated tillage destroys soil structure through physical disruption, and it hastens consumption of organic matter. The nature of the organic amendments which are applied, such as ruminant manure-based compost and emulsified seaweed and fish products can result in the buildup of soluble salts in the plow layer over time. Additionally, continuous vegetable cropping allows insect pest and disease cycles to persist, and stimulates weed seed propagation. Nevertheless, a typical technologically advanced field tunnel represents a substantial investment, and the soil on which it stands is a valuable piece of production real estate, so the simple solution of sacrificing this space to a soil-building green manure crop in alternate years is not an economically feasible option.
An ideal rotation crop is one that makes different demands on the soil from vegetable crops. One such possibility is the cultivation of the almond mushroom, Agaricus subrufescens, and there is much precedent for greenhouse mushroom production in Asia. Mushroom cultivation at first involves the growth of mycelium, which is the “vegetative” part of the fungus consisting of hyphal threads which colonize and digest a substrate, which in the case of most edible mushrooms, is dead or decaying organic matter. Following a period of growth, the mycelium can be stimulated to “fruit”, that is, to start producing crops of mushrooms. Cultures of the mycelium are maintained in a nutrient rich medium for further inoculation of new substrate for subsequent crops.
Kerrigan (2005) places what have been considered three different species, A. brasiliensis, A. blazei, and A. subrufescens, into the latter species through work with DNA sequencing. The following is from a paper by Richard Kerrigan (2005):
Named for its distinctive fragrance and flavour, this mushroom was widely cultivated, sold and eaten in the Atlantic states of the United States from at least Massachusetts to Washington D.C., from the late 19th century into the 20th. Spawn (inoculum culture for farming) of A. subrufescens was even offered for sale. As late as 1918, it was reported to be in cultivation. Commercial production of A. subrufescens subsequently declined as market trends changed; soon the related ‘‘button mushroom’’ species Agaricus bisporus ( J.E. Lange) Imbach appears to have been the only mushroom species being regularly cultivated in the United States.
This fungus is a soil dwelling saprophyte, able to digest lignin, cellulose and organic debris in general (Stamets 2000). It is now cultivated extensively in Japan and Brazil, both for its culinary and medicinal qualities. Unlike most other mushrooms of commerce, it is very productive in the warm humid conditions like that which exist in a greenhouse during a Nova Scotia summer. Economically speaking, almond mushrooms have lucrative potential, yielding from 9 to 15 kg per m2 (Iwade and Mizuno 1997), and selling for $20/kg or more. Thus, a 60’ x 20’ greenhouse could gross between $15,000 and $20,000 per year. Mushrooms in dried form may be worth a great deal more to the pharmaceutical industry due to its well documented cancer-fighting beta glucan content. Stamets (2000) cites several references concerning the isolation of several constituents which are active against tumors or modify immune responses to cancerous cells.
Most commercial production of almond mushrooms takes place in Brazil and Japan, so descriptions of production methods in English are scarce and not altogether exact. Iwade and Mizuno (1997) outlined a method which is similar to typical Button Mushroom (Agaricus bisporus) production in indoor low light conditions using ruminant manure compost, but at a warmer temperature. Stamets (2000) describes indoor production on ruminant manure compost similar to that of the button mushroom, also under warmer controlled conditions. He also mentions sterile sawdust and fresh woodchip, which is virtually sterile, as suitable substrates. Like button mushroom production, both methods use freshly made compost which has not yet been recolonized by any secondary saprophytic fungi.
In Brazil, composted bagasse, a waste product from sugar cane processing, is used as a substrate in outdoor mounded beds (Stijve 2002). Mizuno (2000) describes how in Brazil, freshly composted bagasse, horse manure, grass and various organic and chemical supplements are inoculated with spawn in outdoor piles. This is then allowed to colonize the compost and after 30 days, it is filled into outdoor ditches measuring 25 cm in depth and 30 cm wide. This is then covered over with 6 cm of casing soil. Fruiting begins in 25 days and continues in flushes every 15 days for as much as three months. Mizuno (2000) mentions the use of the “bed block”, a moistened mixture of sawdust, rice bran and nutritional supplement packed into a small plastic bottle and inoculated with mycelia culture and incubated for a period of time. The resulting dense hyphal masses inside the bottle are removed in chunks and inserted into a mushroom production substrate, such as compost. Taguchi et al. (2008) produced mycelium in a 50:50 mixture of sterile sawdust and rice bran, substrate materials cited as cheap and available. Stamets (2000) mentions rye grain as a useful spawn production substrate.
Additional factors may play roles in successful production. A study in Brazil investigated the effect of light on production of mycelium and none was found (Bernardi et al.2009). However, Stamets (2000) claims that light may play a role but its degree of influence has not been characterized. There are also two potential inoculation methods. The standard method of substrate inoculation with button mushroom spawn is called “through mixing”, in which spawn is worked into the substrate homogeneously. Another method described by Iwade and Mizuno (1997) and Mizuno (2000) involves placing concentrated plugs of mycelium (bed blocks) at 20 cm intervals on shaped ridges of substrate. Stamets (2000) claimed success with this latter method, describing the resulting mushroom flush as occurring in “islands”.
Fungal mycelium has the potential to unlock the carbon from wood, an abundant and locally available resource, and convert it into a soil microbial food source. In his book Mycelium Running (2005), author and mycologist Paul Stamets extensively discusses the as-yet untapped human-engineered potential of fungal mycelium to cycle nutrients through the environment. We hope to use A. subrufescens to: produce a high value mushroom crop; maintain and elevate soil organic matter content; and to promote the soil colonization of this saprophytic fungus, which can improve soil structure and nutritional status in beds which are intensively cultivated. We also intend to track the performance of the subsequent vegetable crop in what were previously mushroom beds. In fact, we would like to ascertain whether or not the fungus can survive in the ground of an unheated winter greenhouse, and then continue to grow as an intercrop with the subsequent year’s vegetable crop. To our knowledge, such a scheme has not been investigated.
Another locally available source of organic material with potential for mushroom production is the municipal solid waste (MSW) compost produced at the facility in Lunenburg. Ruminant manure compost is the traditional substrate for Agaricus production, but little work has been done with MSW compost. Stamets (2000) suggests that a nitrogen content of 1.5% to 2% is ideal, and MSW compost from Lunenburg is typically around 2% N (Radin and Warman, submitted for publication). There have been favorable results in button mushroom production with the use of MSW compost as a casing material, which is layered over the top of the mycelial substrate (Lelley et al. 1979) and upon which the fruiting takes place. Little if any work has been done with mushroom production in MSW compost since that time. Therefore, we will use MSW compost as part of both the mycelial substrate and the casing material.
Lastly, we are interested in producing spawn for subsequent almond mushroom crops. We will follow general guidelines as described by Mizuno (2000) and Stamets (2000, 2005).
References cited
Bernardi, E., L.P. Donini, E. Minotto, and J.S. Nascimento. 2009. Effect of media and light conditions on the growth and mycelia mass of Agaricus brasiliensis. Arquivos do Instituto BiolÃgico (SÃo Paulo) 75:375-378.
Iwade, Inosuke and Takashi Mizuno. 1997. Cultivation of Kawariharatake (Agaricus blazei Murrill). Food Rev. Int. 13:383-390.
Kerrigan, Richard W. 2005. Agaricus subrufescens, a cultivated edible and medicinal mushroom, and its synonyms. Mycologia 97:12-24.
Lelley, I.J., A. Hasuk, A.A. Ernst, and W.W. von Stumfeldt. 1979. Municipal-waste composts. Are they a practicable alternative to peat as a mushroom casing material. Mushroom Journal 79:313-315.
Mizuno, Takashi. 2000. Cultivation of the medicinal mushroom Royal Sun Agaricus, Agaricus blazei Murr. (Agaricomycetideae). International Journal of Medicinal Mushrooms 2:215-220.
Radin, A. and Warman, P. Submitted. Assessment of productivity and plant nutrition of Brussels sprouts, Brassica oleracea var. gemmifera, using municipal solid waste compost and compost tea as fertility amendments. Journal of Sustainable Agriculture.
Stamets, Paul. 2000. Techniques for the cultivation of the medicinal mushroom Royal Sun Agaricus, Agaricus blazei Murr. (Agaricomycetideae). International Journal of Medicinal Mushrooms 2:151-160.
Stamets, Paul. 2005. Mycelium Running: How mushrooms can help save the world. Ten Speed Press, Berkeley, California.
Stijve, Tjakko. 2002. Agaricus blazei Murrill- A new gourmet and medicinal mushroom from Brazil. Australasian Mycologist 21:29-33.
Taguchi, T., S. Kawachi, and S. Meguro. 2008. Cultivation of himematsutake (Agaricus blazei) in saw-dust media. Bulletin of the Faculty of Agriculture, Miyazaki University.
Methods
The following design proposal may be subject to slight modifications, depending on unforeseen circumstances. The experiment will take place according to the description below in the first year, but the second year’s study will take place in a second greenhouse and be refined and modified by lessons learned in the first year. The committee will be notified of any such modifications in the interim report. During the second year, the beds of the first year greenhouse will be used to grow a subsequent vegetable crop, and yield data will be collected in order to determine if there are differences in productivity between the treatments. All work will be carried out at Pleasant Hill Farm located on Route 208 in Pleasant River, Nova Scotia.
Experimental design
Experiments and mushroom production will take place in a heated and ventilated greenhouse measuring 18.3 m x 6.1 m. Four existing 91.4 cm wide vegetable beds running the length of the structure will be used to create mushroom growing ditches as described by Mizuno (2000). Each bed will be considered as a separate complete block for experimental design purpose. The production ditches will be excavated in the early spring to facilitate soil warming, and warming will be additionally hastened by overnight heating. Each of four randomized complete blocks will incorporate two factors, substrate mix and inoculation method, and one subfactor, casing material. Substrate mixes will be created in four factorial treatments: 100% woodchip, 66% woodchip/33% MSW compost, 33% woodchip/66% MSW compost, and 100% MSW compost. Substrate will be inoculated either by “through mixing” or by using bed blocks. Each plot, measuring 91.4 cm X 162.6 cm, will have a 25 cm deep and 30 cm wide ditch down the center line. Half of the running length of the ditch (81.3 cm) in each plot will be covered over with native soil, and the other half with MSW compost. The center-to-center distance between each block will be 121.9 cm. The ends of each plot will be separated by a 30 cm space. In total, there will be 8 plots per block (4 substrate mix levels X 2 inoculation methods), each split into two casing soils, and this block will be replicated four times. Beds will be created using approximately equal amounts of substrate, as measured by dry matter weight. Spawn for the first year’s inoculation will be obtained from Western Biologicals Ltd. (P.O. Box 283, Aldergrove B.C. Canada V4W 2T8). Casing materials will also be applied in equal quantity by volume to obtain a 6 cm depth. Substrate temperature and moisture levels will be monitored with soil thermometers and tensiometers, and maintained at or near optimal levels (24 to 26?C and 70%, respectively) using heating/ventilation and micro sprinklers.
All MSW compost used will be screened to pass through 5 mm mesh to remove foreign materials and stones which are sometimes found in this product. Casing soils will be either field soil from the ditches dug in the beds, or cured MSW compost. It is noted in the literature that casing soil should not be sterile, in order to facilitate budding of the mycelium.
Ditches in beds will be filled with substrate mixtures and inoculated in mid to late May, depending on when the 15 cm deep soil temperature reaches 20?C. When substrates are well colonized with mycelium, which may take approximately 4 weeks, casing soil treatments will be applied. Fruiting flushes are expected to begin 3 to 4 weeks after and continue on, although it is unknown for how long.
Using the mushroom plots of the first year, a full complement of approved organic amendments will be applied and vegetable seedlings (as yet undetermined if cucumbers or tomatoes) will be transplanted in the second year. Plants will be fed with supplements as ordinarily practiced and yields will be recorded from all plots. Meanwhile, a new greenhouse will be prepared for a second mushroom production episode, this time refined according to the results of 2010.
Parameters measured
For the purpose of identifying short term economic benefit, mushroom yield records will be maintained throughout fruiting periods. Soil testing will be used to determine the influence of the treatments on soil parameters. Initial substrate and underlying soil pH and electrical conductivity (EC) will be measured, and compared to later measurements following mushroom production. Underlying soil of each greenhouse length block will be initially tested for elemental and organic matter contents before the start of the experiment, and each plot will then be tested during the first autumn after mushroom production has ceased. For the purpose of determining the effect of different substrate treatments on accumulation of mineral elements from MSW compost and how this relates to yield, mushroom tissue from each plot will also be analyzed. Data will be analyzed using a two factor analysis of variance model with split plots.
Significant events and procedures during the course of this two year study include: initial soil sampling (March 2010); bed ditch creation (April 2010, 2011); bed substrate mixing, filling and inoculation (mid May 2010, 2011); application of casing material (mid June 2010, 2011); fruiting flush dates (various points during summer and fall of 2010 and 2011); mushroom tissue sampling (summer 2010, 2011 if necessary); soil sampling (fall 2010, 2011); spawn culturing (fall 2010); data analysis and preparation of interim report (December 2010-January 2011); testing for spawn viability (March 2011); vegetable transplanting into first year mushroom beds (March-April 2011); vegetable harvest (June-October 2011); data analysis and final report preparation (November-December 2011); preparation of refereed and popular press publications, and presentations for various conferences.
Project Deliverables
Upon completion of this project, the investigators expect to have established an Almond Mushroom production system in greenhouse beds, and established presence or absence of various effects on soil properties, as measured by both soil testing and by subsequent vegetable crop performance. It is also expected that a system of spawn production will be established for on-farm use. Throughout the entire project, activities and results will be photographically documented.
Project Benefits and Impact
Although we are aware of one relatively large scale mushroom grower in the province, the successful development of this production system can form the nucleus of a small scale gourmet mushroom industry in Nova Scotia. Unusual mushrooms are a “next step” in direct-retailing for Nova Scotian farmers and a project such as this could stimulate a grassroots industry development. Growth of Nova Scotia farmers’ market sales will continue as the diversity of Nova Scotia products increases. A quick look at the produce section of any large food retailer shows that significant shelf space is devoted to mushrooms, which indicates a high demand. A closer look at the packages reveals the distances which this product typically travels, and the monetary value associated with the more unusual varieties.
At the local level, the dwindling forest products industry needs to be replaced by innovative, homegrown production of goods that are consumable locally and this initiative builds towards food self-sufficiency for Nova Scotia. An industry such as this can also make use of a recovered resource, municipal solid waste compost.
This project is unusual and innovative because it: 1) explores production methods of a highly marketable, high value product; 2) seeks to remediate soil which has had high demand placed on it; and 3) develops a new use for existing farm infrastructure (greenhouse).
There has been considerable effort in thinking through this project: literature searching, personal communications, and high level discussions have been driven by a genuine desire to produce this mushroom and improve these greenhouse beds while doing so. The strong experimental design should provide enough information after the first year to enable us to demonstrate production success during the second year. The only way to achieve this is by investing energy, resources and analytical skill in its investigation.
Applicant’s experience and ability to successfully complete the project
We, the applicants Cindy Rubinfine and David Blanchard, have 30 years of experience as proprietors, both in dairy and vegetable operations, and have spent the last 11 years growing in greenhouse conditions. We have a strong understanding of this growing environment. The farm is organized, both in the field and greenhouses, into a labeled bed system in which the history of each of the 170 of them can be traced. Amendments, crop varieties, production, and sales are all recorded in a database in order to understand the effectiveness of our practices and increase our profitability. Since this farm is certified organic, we apply only approved, non- or least-toxic pest control products, but only out of necessity. We want to encourage the presence of beneficial predator and parasitoid insects by planting pollen and nectar plants known to be attractive. We are committed to building soil quality through incorporation of composted animal manures and undersowing of green manure crops. We follow a crop rotation designed to disrupt pest and disease cycles. In our dairy operation, in which we also raised grass-fed beef, we practiced rotational grazing while also growing our own silage and hay crops. We strive to manage our farm as a long-term agroecosystem, practicing sustainable logging practices in our woodlot, which includes fungal inoculation of stumps with marketable mushrooms that will also recycle nutrients back to the forest floor. We will both be involved in the oversight of all phases of this project, supplying physical labour where needed. We will also supervise a technician, whom we feel must have a strong grasp of this multifaceted project.
Our project leader, Andy Radin, is currently employed by Nova Scotia Agricultural College as a research assistant, working with Dr. Phil Warman on the use of municipal solid waste compost and water extract of compost as vegetable and berry production amendments. One refereed publication has been submitted from this work so far, and three more are currently in preparation. He has an M.Sc. in entomology from the University of Maine and B.Sc. in horticulture and entomology from the University of Wisconsin-Madison. He has published two papers concerning work with trap cropping and host colonization behaviour of the Striped Cucumber Beetle. Andy also produced 3+ acres of organically grown vegetables in the Hudson Valley of New York for 9 years.
Communication plan
Information gathered from this work will be disseminated in a number of ways. Using photography and presentation software, we will be prepared to present our work in indoor, off-season settings such as regional grower meetings and at conferences sponsored by the Organic Agriculture Centre of Canada. We plan to submit a publication to the Atlantic Canada Organic Regional Network (ACORN) and the Canadian Organic Grower Journal. There is also potential for the submission of a publication to a refereed journal. We intend to host more than one field day and possibly a workshop on bed construction, inoculation and spawn production, the latter being a key to self sustaining production. Field days will feature currently producing beds and product available for sampling. We will also make available to the public general information about the project and grant program at farmers’ markets when mushrooms are being sold.