Organic Science Canada- Spring 2022 by OrganicScienceCanada

ORGANIC SCIENCE CANADA SCIENCE FOR PRODUCERS | ISSUE 4 | SPRING 2022

Tending Your Soil Life

A healthy soil contains a staggering number of living organisms P G. 2 3

Can Struvite Fix Our Phosphorus Problem?

Growing Media For Organic Greenhouses

Grazing Cover Crops: You Can Have Your Cover Crop And Eat It Too

P G. 1 1

P G. 1 5

P G. 2 1

About Organic Science Canada Magazine Organic Science Canada magazine is packed with the latest advancements in organic research and innovation from the national Organic Science Cluster (OSC) program. The magazine brings you trends, news and results from across Canada. The scientists who appear in these pages are working hard to improve the sustainability and profitability of organic and low-input agricultural systems. Organic Science Canada magazine is published by the Organic Federation of Canada (OFC), in cooperation with the Organic Agriculture Centre of Canada (OACC). Created in 2007, the OFC is composed of ten organic associations representing

nine provinces and one territory. Collectively, they promote the development of the Canadian organic industry across the country. The Federation is responsible for the maintenance and interpretation of the Canadian Organic Standards and the management of Organic Science Clusters 1, 2, and 3. OFC is based in Montreal. The OACC was formed in 2001 with a mission to lead and facilitate organic research and education. The Centre plays a key role in national efforts to advance the science of organic agriculture. OACC also supports the training of the next generation of organic professionals. OACC’s home base is in Truro, Nova Scotia, at Dalhousie University’s Agricultural Campus.

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

OSC3 (2018-2023) is supported by the AgriScience Program under Agriculture and Agri-Food Canada’s Canadian Agricultural Partnership, and by over 70 partners from the agricultural community. OSC3 has 27 research activities under five general themes: field crops, horticulture, pest management, livestock and environment.

FOR MORE INFORMATION: www.organicfederation.ca www.dal.ca/oacc @OrganicAgCanada @OFC_organic

Table of Contents 3

WELCOME

SNIPPETS

FEATURE: CAN STRUVITE FIX OUR PHOSPHORUS PROBLEM?

INFOGRAPHIC: BOOST YOUR BOTTOM LINE WITH HEALTHY SOIL

GROWING MEDIA FOR ORGANIC GREENHOUSES

DO ORGANIC SOILS NEED REGENERATION?

ORGANIC SCIENCE CLUSTER SUPPORTERS

GRAZING COVER CROPS: YOU CAN HAVE YOUR COVER CROP AND EAT IT TOO

FEATURE: TENDING YOUR SOIL LIFE

ABRI VÉGÉTAL: TASTY ORGANIC CROPS, GROWN SMARTLY

COVER CROPS: A SECRET WEAPON FOR HEALTHY SOIL?

THE MORE THE BETTER?: MULTI-SPECIES VS SINGLE-SPECIES COVER CROPS FOR CARROTS

ECONOMICS VS THE ENVIRONMENT: TRADE-OFFS IN NUTRIENT MANAGEMENT FOR ORGANIC VEGETABLES

Above: A close up of a Velvet Queen sunflower dusted with pollen at the Guelph Centre for Urban Organic Farming. (Photo by Nathalie Amyotte) Cover photo: Garlic harvest. (Photo by Jedidiah Gordan-Moran)

This magazine may be cited as: Geldart, E.. Graves, M.E., Boudreau, N., Wallace, J., and Hammermeister, A.M. (Editors). 2022. Organic Science Canada. Volume 4. Organic Federation of Canada, Montreal, QC and Dalhousie University, Truro, NS. 40 pp. www.dal.ca/oacc/oscIII

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Organic Science Canada: Digging Into Soils renew the soil food web on our farms, and our own bond with it. One of the exciting things about research on organic systems is that it crosses boundaries. Studies on one planting and cropping system gives me ideas for how to change our own cover crop regime on a different crop altogether.

Over the last few years, we have been asked to pivot so much and so fast we could be drilling post holes. As we’ve dug into our soils, we have directly seen and felt the effects of climate chaos- from hydrophobic soils to flood-borne contamination and erosion to lack of nutrient uptake due to drought. Every season brings unique challenges, and perhaps more violent challenges than usual this year (speaking for BC, for certain). This issue of Organic Science Canada provides us with a snapshot of some of the research that can help our soil survive these challenges. Encouraging robust soil life is clearly the best way to create resilience on the farm, whether we are growing hops, carrots, sunflowers or sheep. We know that soil contains multitudes of organisms, but what are they and what do they do? Janet Wallace offers us detailed information on what’s living in our soil (pg. 23). This article focuses on a number of soil organisms, in particular arbuscular mycorrhizal fungi, and their role in soil health. She brilliantly explains, “soil life is, in essence, the foundation of organic agriculture.” This helps us realize that perhaps it’s time to slow down a bit and re-examine that which sustains us – quite literally – and

While cover crops help regenerate soil biology, chemical imbalance is another matter. The loss of phosphorus on organic farms is an ongoing problem. The primary forms of phosphorus available to organic farmers are not always usable due to soil pH, leading to chronic degradation, while manure is not always accessible. Struvite might be the solution, especially since it precipitates easily out of solutions of water combined with human or livestock waste. PhD candidate Joanne Thiessen Martens explains the three-year study that shows great promise in alfalfa crops, with slow release and long effect of struvite, even in alkaline soil (pg. 11). There is still more work to be done, including finding out if struvite from human waste streams will be added to the permitted substances list of the Canadian Organic Standards in 2025.

As organic farmers, we live by the mantra “feed the soil, not the plant,” but sometimes our tillage practices, cover crop and green manure regimes don’t quite get us where we want. Stéphanie Lavergne and Joannie D’Amours discuss cover cropping as a critical tool to build healthy soils (pg. 29). Their article explains the research of Organic Science Cluster 3, Activity 27. This activity aims to address how field management practices and combined approaches can influence soil health and soil carbon dynamics. They explain that preliminary research findings suggest reduced tillage There’s so much incredible research leads to healthier soils and an abundance being done through the Organic Science of earthworms. Cluster that gives us new insight, new Although the use of cover crops can tools and new ideas to implement on our benefit soil health and system resiliency in farms. While the work of OSC3 covers a lot the long term, using cover crops can some- more ground than this issue’s focus on soil times be a short term financial cost for health, we remain rooted in our conviction farmers. Carolyn Marshall suggests cover that healthy soil makes healthy ecosystems crop grazing as a solution (pg. 21). I’ve been and healthy farms. I’m excited to plan this using cover crops between my perennial year’s cover crop rotations and find out hops beds for years, both over summer and more about how to make my farm more winter. I’ve never been really sure how to resilient! I’m also very proud of the work choose which cover crop will really meet done by the Organic Agriculture Centre of my needs, so I rotate and intermix differ- Canada and the Organic Federation of Canent crops. I also – sometimes – kill that ada to enable all these research projects. cover crop (deliberately!) by turning my We know what a difference they make to all sheep into the hopyards in early spring, our farms. giving them an early pasture and reducing the amount of tilling I do. Marshall’s article suggests that there’s not a huge soil health difference between grazing or disking in a cover crop, but my sheep or chickens get a bonus!

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Sincerely, Rebecca Kneen Board member, Organic Federation of Canada

Snippets Margaret Graves, Emma Geldart, Emmanuella Ellis Organic Agriculture Centre of Canada, Dalhousie University

Plots at IRDA. (Photo by Mylène Généreux)

BETTER BABY GREENS: OPTIMIZING THE PRODUCTION OF ORGANIC GREENS IN MUCK SOIL Dr. Caroline Côté of the Research and Development Institute for the Agri-Environment (IRDA) coordinated a multidisciplinary team set out to develop an ideal baby greens production system for muck soil. The work was supported by the Organic Science Cluster 3 and Vert Nature, the corporate farm of VegPro International – the largest vegetable producer in Canada. The primary focus was to manage weeds and insect pests, and optimize yield.

Results showed that composted cattle manure produced significantly higher yields for green romaine lettuce. For spinach, pelleted poultry manure produced the highest yields. The different amendments did not impact weed populations.

Diverse trap crops that incorporated several species were better at attracting the redheaded flea beetle than the amaranth-only trap crop. To establish and maintain an effective trap crop, good irrigation and weed management were shown The irrigation system was monitored by to be important. tensiometers in the soil. A tensiometer is Results from the two seasons demona water-filled tube with a manometer or strated that irrigation played an important pressure sensor and a ceramic tip that is role in stimulating weed emergence during inserted in the soil. It measures the soil the period of stale seedbed. A stale seedmoisture tension, or the strength with bed encourages weed seeds in the soil to which the soil holds water and therefore germinate and are then killed before seedthe strength required by the plant to ex- ing the crop. It does not seem necessary to tract the water. In this case the irrigation irrigate the stale seedbed more than once system was set to come on at water tension based on the results of this study. Plots irvalues between -25 and -30 kPa for lettuce. rigated once or twice had a similar amount Water losses due to evaporation and water of weeds at harvest. taken up by the crop mainly occurred in the The use of bioinsecticides, either alone first ten centimeters of the soil. or combined with natural predators, failed

Two experiments were established in 2018 and 2019 at IRDA's Organic Agriculture Innovation Platform in St-Bruno-de-Montarville, Quebec. One of the experiments The different cover crops that were testproduced green romaine lettuce and spined (forage pea, oat or control) had no effect ach, while the second one produced red on lettuce and spinach yields and did not curled lettuce, red romaine and arugula. impact weed populations.

to reduce harvest damage from insects for red curled lettuce and arugula. The use of natural predators may be of interest in cases where there is no suitable plant protection product.

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Snippets Margaret Graves, Emma Geldart, Emmanuella Ellis Organic Agriculture Centre of Canada, Dalhousie University

The study showed that the flex-tine harrow and the cage weeder have similar effectiveness in controlling weeds with generally more than 90 percent weed suppression. The importance of properly adjusting mechanical weeding equipment was however demonstrated. The flex-tine harrow in particular requires proper adjustment. When it was properly set up for depth and aggressiveness of the tines, it showed potential to be even more effective than the cage weeder. At harvest time in 2018, the final weed density and biomass were similar between weeding treatments. In 2019, weed density was on average 24 percent lower when the flex-tine harrow was used than with the cage weeder. In the second cropping, weed biomass followed the same trend. While the two-year study showed prom- Fava plots at Fourth Sister Farm in August 2021. (Photo by Tiffany Traverse) ising results, more testing is required to Most importantly, this project is indigcontinue observing the trends, particularenous-led. Traverse is of Secwépemc and ly with regard to the use of natural predsettler roots and has designed her farm ators, the impact of irrigation on weeds system with inspiration from her indigeduring stale seedbed and to calculate crop nous mentors. When designing the project, coefficients (the link between daily water she had autonomy over elements like plot withdrawal by the crop and daily reference Tiffany Traverse’s Fourth Sister Farm in size and planting dates, while Shrestha and evapotranspiration). More data is also reteam contributed the experimental design quired to refine weed emergence models. Northern British Columbia is acting as an that includes randomization and a control alternative research lab for integrated systems. With a focus on seeds, wild harvest- treatment. The collaboration is made posing and a diversity of livestock and vegeta- sible by the Indigenous Agricultural SciFOR MORE INFORMATION bles, Traverse is entrenched in community ence Partnerships Program. and contributes in many ways, including This rich farming system and its differTo learn more about Activity 12, to science! ent, closed-loop nutrient sources will be please visit www.dal.ca/OACC/ OSCiii Along with a team of Agriculture and scientifically described via the soil strucAgri-Food Canada scientists, led by Bharat ture, soil life and crop yields. They will look Shrestha, Traverse is investigating the im- at the nutrients present in the soil and pact of five different amendments, com- those taken up by the plants.

ON-FARM COMPOST RESEARCH PROJECT DRAWS ON DIVERSE WAYS OF KNOWING

posted manure from her horses, cattle, An intercultural and rigorously designed pigs, chickens, and vermicompost on heir- experiment to learn from an indigenous loom fava beans and oats. Composting is farm system that keeps livestock and crops done on the farm. tightly interwoven: this project is a beacon of hope.

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Snippets Margaret Graves, Emma Geldart, Emmanuella Ellis Organic Agriculture Centre of Canada, Dalhousie University

MEASURING THE VALUE OF TWELVE YEARS OF ORGANIC SCIENCE CLUSTER RESEARCH

The process involves talking with the people who use the new/improved practices, knowledge and tools that are coming out of the research. We are coming to the end of our consultations with researchers who shared interesting insights about their work and its impact at the producer level. Many of them were excited to talk about their old projects and to see how they have continued to bear fruit (or not, and if that was the case, why not).

What is the value of agricultural research to society and the environment? Has the research created benefits in the “real” world, beyond academia? Evaluating the impact of scientific research will alThe next step is to interact with end uslow us to start answering these questions. Impact is the translation of research into ers of the research outputs. We want to economic, social, and environmental ben- find out if the research is noticed by proefits when the results are put into practice. ducers and know from their point of view if Agricultural research aims to ensure it has benefited them. If you have changed food security while protecting the envi- the way you farm because of a research ronment and addressing challenges with project or findings, let us know!

FOR MORE INFORMATION Smit, P. J. and Hessels, K. L. (2021). The production of scientific and societal value in research evaluation: a review of societal impact assessment methods. Research Evaluation, pp. 1–13 https:// doi.org/10.1093/reseval/rvab002 Morton, S. (2015). Progressing research impact assessment: A “contributions” approach. Research Evaluation 24, pp.405-419 https:// doi.org/10.1093/reseval/rvv016

climate change – these are big goals. Researchers, research facilitators and funders (which for publically funded work, includes the taxpayer) need to know if progress is being made on these goals as a direct result of research. The Organic Science Cluster (OSC) program has been running since 2009. We want to know if a decade of OSC research has changed the way organic agriculture is practiced in Canada. Using the scientific literature on research impact as a guide, we developed a framework to get these answers. It’s a 6-step evaluation process that links inputs, outputs, outcomes and impacts. It is built around five categories of impact: social, economic, environment, policy and human capital (people trained). The framework also sets the stage to measure the benefit from future projects.

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Snippets Margaret Graves, Emma Geldart, Emmanuella Ellis Organic Agriculture Centre of Canada, Dalhousie University

A student taking a break from pasture evaluation in 2007 in Brookside, NS. (Photo by Nancy McLean)

ORGANIC SHEEP HELP SOLVE A PARASITE MYSTERY All sheep producers have their work cut out for them when it comes to managing gastrointestinal nematode parasites (aka worms). One difference that organic sheep producers face is that they can’t use dewormers routinely. Clause 6.6.11 of the Canadian Organic Standards outlines the exceptional circumstances when dewormers can be used. These restrictions are challenging, but in the case of Haemonchus in Eastern Canada, they helped organic producers avoid drug-resistant parasites. We learned about this in a recent interview with Drs. Paula Menzies and Andrew Peregrine, both veterinarians, professors and researchers at the University of Guelph.

In Ontario a decade ago, there was a significant increase in sheep deaths due to Haemonchus contortus (barber pole worm). One parasite can lay 10,000 eggs per day – and 1,000 worms in a lamb’s gut can drain the animal’s blood and kill it in a few weeks. There was also an usually high amount of drug resistance showing up in Haemonchus – dewormers were no longer working against it on some farms. Because the parasite was an issue for all producers, the Organic Science Cluster 1 (2009-2014) funded research into the Haemonchus life cycle. Dr. Menzies (now retired) and Dr. Peregrine found that Haemonchus did not overwinter on Ontario and Quebec pastures, as some worms do. Ewe flocks were being dewormed during the winter; only eggs from the parasites that could survive the winter deworm-

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

ing ended up on spring pastures. These drug-resistant worms reproduced quickly and infected ewes and lambs, leading to high mortality. The practice of winter deworming selected for fast development of drug resistance. The solution for this problem, which has been promoted widely for years, is the strategic use of dewormers: only deworm the individual sheep that need it, when they need it. Other practices are also needed, such as selecting breeding stock that are better able to develop immunity to parasites, monitoring fecal egg counts, and evasive grazing. Canadian sheep are healthier overall as a result of the research, which benefitted from the observation of different outcomes on organic and conventional farms.

Snippets Margaret Graves, Emma Geldart, Emmanuella Ellis Organic Agriculture Centre of Canada, Dalhousie University

ON-FARM SEED RESEARCH PUNCHES ABOVE ITS WEIGHT Farmers across Canada benefit from being direct partners in selecting and testing new varieties of vegetables and grains. They report gaining practical skills, community connections and resources, and new market opportunities – a ripple effect that goes beyond new varieties bred for organic. Shannon Jones and Bryan Dyck run Broadfork Farm, an organic mixed vegetable farm in Nova Scotia. They are one of many farms across Canada that have done vegetable variety trials as part of the Canadian Organic Vegetable Improvement Project (CANOVI). Jones and Dyck trialed different varieties of rutabaga, red carrots and peppers. For the rutabaga, they evaluated the smoothness and uniformity of the roots, and for their own interest, they also compared the flavor. CANOVI research is supported by the Organic Science Cluster 3 and The Bauta Family Initiative on Canadian Seed Security (a program of SeedChange). Its [older] sister project, a field crops participatory plant breeding program based in Manitoba, has now been running for nine years. Participatory plant breeding allows farmers, plant breeders and other stakeholders to work together to develop new varieties – and the research has shown that the varieties excel.

A seed crop of Dakota Tears onions at Broadfork Farm in August 2021. (Photo by Emma Geldart)

part in the participatory plant breeding or Hanson under the guidance of Dr. Hannah variety trials. Wittman. They are breeding carrots, pepA recent survey conducted by The Bauta pers and more. The field crops program Initiative shows that 93 percent of partici- breeds oats, wheat and potato, and is based at the University of Manitoba’s Natupating farmers learned to implement variral Systems Agriculture lab under Dr. Martin ety trials on their own farms. At Broadfork Entz’s leadership. Farm, Jones explains that this can be really helpful when they’re direct marketing to customers. Armed with the details from FOR MORE INFORMATION their on-farm data collection, they can explain exactly what’s special about the va“Is it a Turnip or Rutabaga? riety. Growing some special varieties” “We often do variety trials on our own,” says Jones, “expanding from that, it’s nice to be part of something larger.” She conveys that the trials are an opportunity to try interesting varieties that could otherwise be hard to find. Across the country, almost 50 percent of farmers who did the vegetable variety selections and trials started selling vegetable seed commercially, diversifying their businesses as a direct result of the program.

One of the unique things about these projects is the level of engagement across Canada, facilitated by a strong network of farms, researchers and Bauta Initiative regional coordinators. Since 2013, more CANOVI is based out of the Universithan 175 farmers coast to coast have taken ty of British Columbia, led by Dr. Solveig

https://broadforkfarm.com/ is-it-a-turnip-or-rutabaga-growing-some-special-varieties/ Canadian Organic Vegetable Improvement Project https://www. seedsecurity.ca/en/programs/creating-seed-diversity/302-canovi Participatory Plant Breeding for Canadian Organic Crop Production https://www.umanitoba.ca/outreach/naturalagriculture/ppb.html

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Snippets Margaret Graves, Emma Geldart, Emmanuella Ellis Organic Agriculture Centre of Canada, Dalhousie University

A chicken on pasture at Rosebank Farms in BC in 2018, where some of the pomace feeding trials have been held. (Photo by Margaret Graves)

CRANBERRY AND BLUEBERRY BYPRODUCTS: OUT OF THE GARBAGE AND INTO THE GUT

We recently interviewed Dr. Moussa Diarra, a researcher working with AAFC Pacific Agri-Food Research in Guelph. He made it clear that chicken gut health is a significant hurdle for the sustainability of meat bird production. As a possible solution, Dr. Diarra has been testing organic blueberry and cranberry pomaces as feed A new feed ingredient is waiting in the additives for organic broiler chickens wings that ticks all the boxes for an ef- to boost their immune systems against fective organic solution. It’s a byproduct, pathogenic infections. so its use in feed decreases food waste. Dr. Diarra’s research found that getting It’s multifunctional, in that it encourages the pomace out of the garbage, where it good bacteria, kills bad bacteria like Salhad previously been going, and into the monella and E. coli, and, stimulates chickgut of chickens improved the birds’ health. en’s immune systems and metabolism. It provided similar growth performance as What is this new innovation? It’s leftover the antibiotic bacitracin in feed and has mush (pomace) from juicing cranberries even more beneficial effects for the birds and blueberries. than just killing microbes: the pomaces

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

promoted a healthy immune response and a healthy gut microbiome. If fruit pomaces became widely used in chicken feed, it could mean higher productivity, profitability, decreased waste, and improved animal and public health benefits. This work has generated interest among both organic and conventional producers who are excited at the prospect of a safer and effective way of managing pathogenic bacteria. The next steps are to refine the processing and formulation of fruit pomace as a cost-effective feed ingredient. This cutting edge work has also set the stage for research on the use of other fruit by-products, like blackberry and guava, to fight pathogenic bacteria in fresh produce and in other types of livestock.

Snippets Margaret Graves, Emma Geldart, Emmanuella Ellis Organic Agriculture Centre of Canada, Dalhousie University

2021 PHOTO CONTEST WINNER The OACC is pleased to announce Yulia Shcherbakova as the winner of the 2021 photo contest! Thank you to all who submitted photos.

CLUSTER MANAGEMENT TEAM Meet the team behind the Organic Science Cluster!

Organic Federation of Canada Nicole Boudreau Cluster Manager; OFC Coordinator Emma Bryce Communications Manager

Organic Agriculture Centre of Canada, Dalhousie University Dr. Andrew Hammermeister OSC Science Director; Director, OACC Margaret Graves Program Manager Emma Geldart Communications Officer Emmanuella Ellis Research Associate Rebecca Veenhuis Program Assistant A male bumblebee sticks out its tongue mid-flight after collecting nectar from a zinnia at UBC Farm. (Photo by Yulia Shcherbakova)

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

F E AT UR E S T ORY

Can Struvite Fix Our Phosphorus Problem? JOA NNE T HIE S SEN M A R T ENS P H . D . C A ND ID AT E , D E PA R T M E N T O F S O IL S C IE N C E , U NI V E R S I T Y O F M A NI T O B A

The struvite fertilizer Crystal Green®, produced by Ostara Nutrient Technologies from municipal wastewater, was used to test the response of organically managed crops to this novel nutrient source. (Photo by Joanne Thiessen Martens)

Organic farming has a phosphorus problem. Exporting nutrients off the farm without replacing them depletes soil phosphorus and eventually reduces crop yields. This problem is especially common in longterm organic systems if livestock manure is scarce and the soil is alkaline.

tionally and provides manure for compost. Neighbouring farms don’t have excess manure to sell, and other permitted phosphorous sources (e.g., rock phosphate) are either ineffective in the alkaline, clay soils or too expensive to apply on a field scale (e.g., bonemeal).

Meanwhile, our lakes have a different phosphorus problem. Nutrients exported from farms in agricultural products travel through the food chain (including our bodies), enter waste treatment systems and finally waterways, where they can contaminate water and stimulate algal blooms.

Crops, particularly legumes, have stunted growth, the farmer notes. “That severely affects our ability to grow a good green manure crop to replenish nutrients. We need a solution to this problem soon or it threatens our future in organic production.”

What if it were possible to solve both problems at once, by recycling ‘waste’ nutrients back to organic farmland in a clean, easy-to-use, affordable, phosphorus-rich fertilizer? According to Kim Wilton, an organic grain farmer in central Manitoba, that possibility “would be a game-changer” for her operation. That possibility is in the process of becoming a reality in Canada.

THE PHOSPHORUS PROBLEM The phosphorus problem is more critical in certain areas. On one organic grain and livestock operation in Manitoba, the lack of a suitable phosphorus source is the farm’s greatest challenge, despite having a sizeable livestock herd that is grazed rota-

STRUVITE: A RECYCLED FERTILIZER Recycling nutrients from human waste back to farmland could address the phosphorus deficiency and the degradation of water bodies. For example, in this ‘circular economy,’ struvite can be recovered from municipal wastewater and repurposed as phosphorus fertilizer. Struvite is a mineral consisting of magnesium, phosphate, ammonium, and water held together in a crystalline structure that precipitates naturally under the right conditions. When produced under carefully controlled conditions in wastewater treatment facilities, struvite crystals contain very low levels of contaminants and form granules that can be used as a fertilizer.

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Struvite is unique among fertilizers. Unlike common synthetic fertilizers, struvite doesn’t dissolve well in water. This gives it a reputation as a ‘slow-release’ fertilizer that does not overwhelm the soil system with a large pulse of nutrients. However, struvite is more soluble in soil than rock phosphate, especially in alkaline soils where rock phosphate provides little benefit to crops. With an N-P-K analysis of 5-28-0, struvite is a more concentrated phosphorus source than most fertilizers permitted in organic production, with a lower price per unit of phosphorus. Its low solubility may reduce the risk of losses to the environment by runoff. These qualities have led many experts to recommend that struvite be permitted for use in organic agriculture to help address phosphorus deficiencies. Many organic farmers agree. Dan DeRuyck, an organic grain and beef producer in south-central Manitoba, welcomes a new way to replenish soil phosphorus on his farm. “I am hoping that struvite will be a product we can use in organic production,” DeRuyck says. “I like that it comes from a recycled process instead of being mined, which we will eventually run out of. This product will give me another tool in my crop production.”

Struvite from livestock- or plant-based sources was added to the 2020 Canadian Organic Standards Permitted Substances List (PSL). However, even though the principles of organic agriculture emphasize recycling of materials, human-sourced struvite is not permitted due to concerns about contaminants. Unfortunately, the only commercially available struvite in Western Canada is human-sourced.

MANAGING A NOVEL NUTRIENT SOURCE Because of struvite’s unique properties, we know very little about how to manage it well as a fertilizer. Research has shown that soil properties, plant species, and struvite granule size can all influence crop response. Also, phosphorus may continue to be released long after the growing season, even in the second or third year after application. With the support of Organic Science Cluster (OSC) 3, I conducted field experiments in 2017–2019 as part of my doctoral research to test the effect of different struvite application rates on the yields of spring wheat, flax, and alfalfa-grass forage. The study site near Libau, Manitoba, was typical of many organic farms in the region. With a history of alfalfa hay export and no application of nutrient sources, soil test phosphorus was extremely low and crop productivity had declined over the years. The alkaline soil provided a challenging testing ground for struvite, which tends to work better in neutral or acidic soils.

Ph.D. student Joanne Thiessen Martens harvests wheat from plots fertilized with struvite at Libau, Manitoba. (Photo by Martin Entz)

For wheat and flax, we applied struvite in the furrow with the seed at three different rates, as well as an unfertilized control treatment. The experiment was repeated in each of the three study years. For the alfalfa-grass forage, we applied struvite to an existing forage stand in spring of 2017 by banding it about an inch below the surface, again at three different rates plus a control. We monitored the crop response over a three-year period. Results were mixed. Wheat showed a moderate response, with slightly higher yields attained with every increase in struvite application rate. The highest application rate, which was double the recommended rate for that soil, yielded an average of 38.9 bu/ac over the three years of the study, a 35 percent increase over the

Table 1. Wheat and flax grain yields when fertilized with different rates of struvite in experiments. Results are averaged over three study years. *

Phosphorus* application rate, as struvite

Wheat yield (bu/ac)

Flax yield (bu/ac)

0 lb/ac P

28.5

19.5

18 lb/ac P

31.7

19.7

27 lb/ac P

34.6

19.4

36 lb/ac P

38.9

20.3

unfertilized control (Table 1). Flax yields, on the other hand, did not change with struvite application, hovering around 20 bu/ac for all treatments. The alfalfa-grass forage responded strongly to struvite, especially in the second and third years after application. In the first year (2017), the highest struvite application rate increased forage yield by 65 percent over the unfertilized control treatment (Figure 1). In the second year, the plots receiving the highest struvite rate yielded more than double the control; in the third year, the difference was more than triple. This pattern was caused partly by increases in yield over time in the plots with the high application rate, but also by a decline in the unfertilized control yields over time. Dr. Kim Schneider, assistant professor at the University of Guelph and colead of this OSC3 project, finds the difference in response among crops to be particularly interesting. “We need to continue to understand the mechanism by which some crops can access struvite and some can’t, and then put this to work in our farming systems!” Dr. Schneider explains.

To convert the P application rate to P2O5, multiply by 2.3.

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Annual forage yield (lb/ac)

7000

of two small watersheds within an alfalfa-grass hay field and monitoring the phosphorus in the spring snowmelt runoff, it’s possible to see whether phosphorus from struvite is leaking out of the soil into the environment.

6000 5000 4000 3000 2000 1000 0

2017 0 lb/ac P

2018 27 lb/ac P

53 lb/ac P

2019 80 lb/ac P

Figure 1. Total annual forage yield (sum of two cuts) from alfalfa-grass forage fertilized with different application rates of phosphorus as struvite. Struvite was applied in the spring of 2017.

One approach is to use the slow-release properties strategically in our crop rotations. In the wheat and flax experiments, we found remnants of struvite granules in the soil one year after application, meaning that more struvite could be released for the next crop. By better understanding how struvite interacts with soil over time and how different crops use struvite, we may be able to develop specific guidelines for when to apply struvite in a crop rota-

The preliminary results are very promising. Soil test phosphorus has increased in the part of the field fertilized with struvite but phosphorus concentration in the snowmelt runoff is the same as the area where no struvite was applied. Wilson explains, “this indicates that there doesn’t seem to be a large amount of that residual soil phosphorus being lost through leaching into snowmelt.”

FUTURE OUTLOOK

Our results so far suggest that struvite tion to provide the most benefit to a series can be a very good fit as a soil amendment of crops. in organic cropping systems. It is an affordAnother question was raised: how will able phosphorus input that is effective in struvite’s slow-release over time affect the alkaline soils for at least some crops, with potential loss to the environment? low risk of environmental losses. It also Dr. Henry Wilson, research scientist at aligns well with organic principles. There is the Brandon Research and Development still much to learn about how to use it most Centre of Agriculture and Agri-Food Cana- effectively, but our knowledge is growing da and the other co-lead of this project, is with every new experiment. addressing this. By applying struvite to one The main hurdle is to either develop livestock- or plant-sourced struvite supplies or to add human-sourced struvite to the PSL. “If it gains full certification, struvite represents a viable option for organic farmers to help replenish phosphorus reserves on their farms, something particularly relevant to Prairie regions without a supply of livestock manure,” says Schneider. That would be a game-changer indeed.

Researchers are collecting spring snowmelt runoff from fields with and without struvite applied to see if phosphorus is leaking from the soil into the environment. (Photo by Henry Wilson)

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Infographic

DA L .CA /OAC C/O S CIII

@ OR GA NICAGCA N A DA

@ OF C _ OR GA NIC

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Growing Media For Organic Greenhouses JA NE T WA L L ACE

The demand for organic food continues to rise in Canada. Given our long winters and year-round consumer demand for fresh, locally-grown vegetables, there is increasing interest in organic greenhouse produce. However, as of 2019 only six percent of Canadian greenhouses were certified organic.

• “Be composed of at least 10 percent by volume of compost (exception: seedling/ starter mixes may contain less than 10 percent compost if needed to ensure adequate germination/rooting);" and;

• “Contain at least two percent by dry weight or volume (whichever unit of measure is appropriate) of minerals (sand, silt Transitioning to organic production may or clay, excluding perlite and vermiculite) seem daunting for conventional green- at the start of a production cycle.” house operators, particularly those growOSC research has shown that yields of ing hydroponically and relying on synthet- organic greenhouse tomatoes can be as ic fertilizers and pesticides. Because the high as non-organic yields . However, acfoundation of organic agriculture is soil, cording to OSC researchers Drs. Valérie hydroponics is not permitted and there are Gravel and Martine Dorais, “Organic fertilstrict requirements for the composition ization is often unbalanced” in greenhousand minimum amount of growing media es. Fine-tuning the nutrient supply is more each plant can access. Fortunately, over challenging in greenhouses than in fields the last three Organic Science Clusters where growers can build up the soil qual(OSC), Canadian researchers have been in- ity and soil life over years and throughout vestigating how to create an ideal growing crop rotations. In greenhouses, there is a media and provide a balanced supply of nu- high demand for nutrients given that the trients to greenhouse crops. annual yield per area is often 10 times that According to the 2020 Canadian Organic of field crops. A good crop of greenhouse Standards, the growing media for container tomatoes (e.g., producing of 50 kg/m2) can crops and other greenhouse crops (as de- require as much as 1250 kg N/ha. fined in Section 7.5) must: A successful organic greenhouse is a • “Contain a mineral (sand, silt or clay, finely tuned system where operators, with excluding perlite and vermiculite) and bi- the help of soil life, synchronize the release ological fraction, which contribute to the of nutrients from soil amendments with physical soil structure;" nutrient requirements of the crops. This is particularly difficult for seedlings. As Dr.

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Dorais states, “the amount of fertilizer that should be added to the medium has to be low enough so the salinity does not cause damage to the developing root system but high enough to sustain plant growth up to transplanting.” Salinity, which is measured through electrical conductivity (EC) readings, can inhibit germination and stunt seedlings. A high proportion of compost or other organic fertilizers can lead to high salinity. Salinity is less of a problem when compost is based on plant materials rather than manure. One approach is to provide slow-release nutrient sources, such as compost, in growing media and supplement through topdressing and liquid nutrients. Gravel’s team found that in raised bed containers, organic tomatoes grown in a peat-based medium had yields as great as non-organic tomatoes grown on a coir-based medium, but only in the second year the medium was used. In the first year, the plants may have suffered from a lower release of nutrients due to less microbial activity. In the second year, the microbial community was more established. Introducing microorganisms to the growing media can help transform nutrients into forms plants can use. For example, Dr. Gravel found that Trichoderma harzianum (Rootshield®) stimulated biological activity. In strawberries, applications of T. harzianum led to higher levels of the polyphenols and anthocyanins (phytochemicals linked with flavour and human health benefits). Laval University’s Pierre-Paul Dion found that different organic fertilizers had different effects on soil life, which affected how quickly nutrients were released. Alfalfa meal provided slow, long-term N release. In contrast, blood meal and feather meal provided quick, short-term N. Shrimp meal and pelleted poultry manure provided “a better-balanced organic fertilization supporting diversified microbial communities and reducing the need for mineral inputs to sustain plant nutritional requirements other than N.” However, half of the nitrogen in

the pelleted poultry manure was released quickly; this could damage plants if the application rate is too high. Supplying nutrients is one issue; keeping nutrients in the soil until needed is another. This is where biochar can play a role. Various OSC activities have studied how biochar can retain nutrients (thereby reducing leaching) and stimulate soil life. Adding 15 percent biochar (by volume) to the growing media led to increased yields of sweet peppers and tomatoes. Dr. Vicky Lévesque explains that the improved growth was due to an increase in available nitrogen and phosphorus, and that the biochar led to greater establishment of plant-beneficial bacteria. Efficacy depends on what materials and temperatures were used to create the biochar. OSC studies are giving operators more tools to optimize organic greenhouse production. Future OSC research may bring even more needed insights. This can enable more conventional operators to make the transition to organic production and help meet the ever-growing demand for local, organic food.

FOR MORE INFORMATION Organic Greenhouse Advances: Root Environment and Wastewater Management, found here: www.dal.ca/oacc/bulletin.

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Do Organic Soils Need Regeneration? N I C O L E B O U D R E AU O R G A N I C F E D E R AT I O N O F C A N A D A

The word 'regenerative' is appealing: we all want to regenerate! It is a promise of prolonged youthfulness, of vitality for both our people and our soils.

terials used to maintain and improve soil health must not contaminate crops, soil and water (excess nutrients, pathogens, heavy metals or other prohibited subRegenerative agriculture is being pro- stances) (5.5.4). In fact, Section 5.5.2 is moted everywhere, both by the proponents devoted to the ecological application of of conventional intensive agriculture, such animal manure. as General Mills, and by the Rodale InstiManagement of pests (insects, distute, which created a whole new form of eases and weeds) includes cultural organic certification by providing specific practices (crop rotations, resistant varequirements for regenerative practices. rieties and maintenance of a balanced How does organic agriculture fit into this ecosystem), mechanical methods (tillage, context of promoting regenerative agri- mulching) and physical methods (such as culture? Is there a practical need to re- burning weeds). generate organic soils? Does the Canadian The Organic Standards clearly place Organic Standards (COS) include practices soil fertility at the forefront. In fact, the that care for the soil? COS prohibits hydroponics and aeropon-

A FOCUS ON SOIL FERTILITY

After tillage has been used, the producer might plant a forage crop, sow a green manure, mulch the soil or find another way to provide ground cover. In doing so, soil life is supported and the soil aggregates that support soil structure are re-established. As demonstrated by researchers like Dr. Derek Lynch of Dalhousie University, these practices can largely compensate for the much-discussed disadvantages of tillage. Furthermore, tillage is a valuable tool in incorporating green manures, crop residue and other organic matter that helps feed ics. Since regenerative agriculture places soil life. 'no-till' as an essential practice for maintaining soil health, how can we ensure that MAINTAINING HEALTHY SOIL organic soils remain healthy when tillage is Using catch crops (5.4.2 a) between used to control weeds? Is an organic soil a cropping seasons traps nutrients to limit healthy soil? leaching and keeps the ground covered. They (and other cover crops) also protect WHAT MAKES HEALTHY SOIL? the soil when planted between crop rows.

Soil is the foundation of organic production. Section 5.4 of the COS, Soil Fertility and Nutrient Management, specifies that organic farmers shall establish and maintain soil fertility by preserving and increasing soil organic matter, while aiming for an optimal balance of nutrients and stimulatSoil health is a moving target. Weather ing soil biological activity. conditions, crop type, farming practicSoil fertility is promoted through crop es, seasonal cycles…all these factors and rotation, including green manures, catch more influence soil quality and fertility. crops, legumes or deep-rooted plants The challenge for any producer concerned (5.4.2 a); the use of compost and animal about preserving soil health is to maintain manure (5.4.2 b); and tillage that main- the balance, to analyze the impact of the tains the physical, chemical and biological farming practices applied season after condition of the soil. Organic farmers are season and adjust accordingly. For examrequired to minimize damage to the soil ple, after growing crops with high nutristructure and prevent erosion (5.4.3). ent demands, the soil will be treated with Furthermore, the plant and animal ma- particular care. Its nutrient reserves and

organic matter can be replenished by sowing cover crops or green manure crops, or applying compost to protect and feed the soil microorganisms.

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

It should also be noted that the prohibition of reliance on synthetic fertilizers, fungicides and insecticides in organic production preserves the vitality of soil life. The soil organisms break down organic matter and make it available to plants, an important parameter of soil health. The principles and practices of the COS therefore benefit soil health. The Regenerative Organic Alliance (of which Rodale is a key member) has developed Regenerative Organic Certification (ROC). This requires

basic organic certification for any product that qualifies as regenerative. Regenerative organic certification distinguishes itself by placing greater emphasis on permanent cover for crop land. In reality, organic fields are most often covered. One rarely sees bare organic soil because of the requirement to maintain soil fertility (5.4.1) through crop rotation, by growing green manures and applying compost, aged manure and other organic materials.

SOIL REGENERATION IN GREENHOUSES Since 2009, the Canadian Organic Standards allow plants, usually greenhouse crops, to be grown in containers but only under strict restrictions (7.5). This includes a minimum volume of soil according to the type of crop and culture. Minimum

conditions must be respected in order to maintain the health of the soil in the containers. The physical structure of the soil must be composed of a mineral fraction (sand, silt, clay) and an organic fraction. The soil shall contain at least 10 per cent by volume of compost and at least two per cent of minerals by dry weight or volume. Additional compost applications should be part of the fertilization program (7.5.2.4 a). The COS also recommends soil regeneration in greenhouses and similar structures through the introduction of biodegradable plant mulches (straw or hay) (7.5.9). In addition, substances in Table 4.2 of the Permitted Substances Lists can be used to maintain soil fertility in containers. Unhealthy soil is not fertile, so the COS focuses extensively on soil health in greenhouse production. However, greenhouse products will never be labeled 'grown under regenerative agriculture' given that

the current standard for Regenerative Organic Certification does not allow crops to be grown in containers, other than for seedlings that will later be transplanted in the field. The Canadian organic industry's choice to include greenhouse production in the COS is legitimate as greenhouse production extends the growing season and provides much needed fresh greens and vegetables to those in colder climates. Are organic soils healthy? The COS is reviewed every five years to reassess or introduce best practices that will maintain soil fertility. Soil quality depends on the combination of practices applied season after season. It arises from the balance between the supply of nutrients to the soil and the assimilation of nutrients by the plants. The soil regenerates itself when organic practices are applied consistently year after year.

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Organic Science Cluster Supporters

With great appreciation, we would like to acknowledge the following industry partners for their contributions in support of Organic Science Cluster 3. MONETARY CONTRIBUTIONS

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Organic Science Cluster Supporters

LEFFERS BROTHERS ORGANICS

LAUNDRY VINEYARD

THE MARTENS FAMILY ORGANIC RESEARCH ENDOWMENT

PRIVATE SUPPORTER OF BC AGRICULTURE

ORVAL G. CALDWELL AND H. RUTH GARDNER CALDWELL FELLOWSHIP IN SUSTAINABLE AGRICULTURE/AGROECOLOGY

IN KIND CONTRIBUTIONS

DUBAN FARMS

OVER 150 MORE INDIVIDUAL FARMS

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Grazing Cover Crops: You Can Have Your Cover Crop and Eat It Too C A R OLY N M A R SH A L L N O VA S C O T I A F E D E R AT I O N O F A G R I C U LT U R E

A close up of of hairy vetch, a high biomass, high nitrogen supplying cover crop. (Photo by Carolyn Marshall)

Incorporating cover crops into crop rotations is a widely accepted best management practice for a variety of reasons. The definition of a cover crop is broad and encompasses any crop whose main purpose is not to be harvested for sale.

The majority of research in using livestock to graze a cover crop has occurred in the Midwestern United States, although Dr. Martin Entz at the University of Manitoba and his collaborators have often advocated for incorporating livestock into crop rotations through the use of forages. However, trials are happening, including small on-farm trials of grazed cover crops in Nova Scotia.

needs of both the soil and livestock can often be met by using cover crop mixes – often combinations of grains, legumes, brassicas, and other broadleaf plants such as sunflower. For example, well planned mixes can provide the right mix of protein for a growing cow while avoiding some of the potential risks, such as bloat, and provide soil benefits such as suppressing soil nematodes.

Cover crops are grown to improve or protect the soil and this can be achieved in many targeted ways. They can be chosen for the purpose of reducing soil erosion in a period when the soil would typically be When choosing to adopt cover crop grazMany of these studies of grazed cover bare (the literal definition of a “cover” crop), ing, you are not just choosing plant species crops have similar findings. There is little to break up a disease cycle, add nutrients, to address your soil needs, you’re also con- improvement of soil health compared to build organic matter, and reduce nutrient sidering the needs of the livestock. The cover crops terminated without livestock, leaching, among other uses. This wide variety in uses for cover crops means that there are many decisions to be made when incorporating cover crops into a rotation. Plant species, time of planting, time of termination, and method of termination all need to be decided. In terms of method of termination, cover crops can be: • Terminated chemically (in non-organic systems), • Terminated physically, either with tillage or a no-till crop roller, • Timed so they are winter-killed Another method that has not received much attention in Canada is grazing by livestock. Rolling vetch: One of the termination methods to choose from, using a roller crimper to no-till terminate. (Photo by Carolyn Marshall)

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

"The more you farm like nature, the more it can reduce your inputs and the more money you can make”.

although several studies have shown increases in soil aggregate stability – an important soil measure that can, for example, impact susceptibility to erosion and soil microbial activity. However, many of these studies are only a few years in duration. —Ray Archuleta, Conservation Agronomist with NRCS in the Since soil carbon pools are large and take documentary Kiss the Ground years or even decades to show changes due to management, longer-term studies A North Dakotan rancher, Gabe Brown, could reveal impacts on soil health not de- tem builds resiliency, which is only going to tectable over shorter time frames. grow in importance as we face a changing appears in the documentary Kiss the Ground (available on Netflix). He uses liveWhile these small gains in soil health climate and shifting weather patterns. stock to winter graze his cover crops. When may be discouraging at first, those same Use of cover crops can often be a (shortstudies often concluded that incorporating term) financial cost – although the long- asked about the environmental issues and livestock into the rotation through cov- term benefits can certainly add up in soil concerns around animal production, he reer crop grazing had an economic benefit. health and system resiliency. However, sponds, “The problem isn’t the animal, the So, while incorporation of livestock into incorporating grazing can turn this cost problem is where the animals are at”. After cropping systems will make operations into a gain. This could make cover crop- years of crop loss through weather events, more complicated, there is potential to not ping more appealing to a wider range of the diversification of his operation has imonly increase profitability, but also create producers, provided they can access the proved his bottom line. “I build resiliency in economic stability through diversification. knowledge and support to get a cover crop an ecosystem.” This type of diversification in a farm sys- grazing system going.

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

F E AT UR E S T ORY

Tending Your Soil Life JA NE T WA L L ACE

Picture a flock of sheep on lush pasture. Now flip the image, as though you’re looking at a reflection in a still lake. Consider that there is likely an equal weight of life forms – plants, insects, other invertebrates and microorganisms - in the soil. Organic farmers don’t just take care of the plants and animals living on the soil surface, they also feed and protect soil life. A healthy soil contains a staggering number of living organisms. A handful of healthy soil may contain more living beings than the global human population. These organisms are essential for the health of organic crops and livestock. From mites to moles, earthworms to endophytes, there is a great diversity of creatures living in the soil. We will focus on microorganisms (e.g., bacteria, fungi, protozoa) and invertebrates (e.g., earthworms, nematodes, beetles).

THE LEADERS OF THE UNDERGROUND

Arbuscular mycorrhizal fungi (AMF) are fungi with symbiotic (mutually beneficial) relationships with the roots of many plant species, other than brassicas (e.g., canola, cabbage). AMF essentially increase the surface area of roots, which improves the ability of plants to extract water and nu-

that help bind soil particles together. They also move microorganisms and nutrients throughout the soil. Rhizobia are bacteria that live within the roots of legumes. They fix nitrogen from the air, which becomes available to other plants after nodules are shed from the roots of living legumes or when legumes are incorporated into the soil.

Soil life is, in essence, the foundation of organic agriculture. Microorganisms and invertebrates help plants access nutrients and water, and protect plants from disease.

CONTRIBUTION OF SOIL LIFE

Soil life is, in essence, the foundation of organic agriculture. Microorganisms and invertebrates help plants access nutrients and water, and protect plants from disease. Organic Science Cluster (OSC) research has explored how farmers can protect soil life so the organisms can perform trients, particularly phosphorus, from the the following critical roles. soil. AMF also help protect plants from disease-causing fungi (including Fusarium Decomposition

and Pythium), harmful nematodes and othMany life forms are active decomposers. er stresses, such as drought and extreme Insects and arthropods, like sowbugs, start Actinomycetes are bacteria that give heat. AMF also improve soil structure. the process followed by microorganisms. soil its ‘earthy’ smell and leave thin filaEarthworms are an effective indicator This demolition team releases nutrients ments which contribute to soil aggregation. They aid in nutrient cycling, help con- species because they are simple to count contained in plant and animal material, trol root disease by inhibiting pathogens, and their abundance reflects overall soil including composted manure, cover crops health. Earthworms improve soil porosity and crop residue. Burrowing organisms and promote plant growth regulators. and structure by creating tunnels, which (e.g., earthworms) help transport decomallow air and water to infiltrate the soil, and posing material and nutrients throughout lining these with nutrient-rich substances the soil.

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Cover crops provide food for soil life and protect their habitat in many ways, including moderating soil temperature and reducing the risk of erosion. (Photos by Janet Wallace)

Nutrient cycling In addition to releasing nutrients from decomposing organic matter, soil microorganisms also convert nutrients from minerals and gases into forms that plants can use. In nitrogen fixation, rhizobia capture nitrogen from the air; other (nitrifying) bacteria transform the ammonium to nitrite then to nitrates for plants to use. OSC researcher Dr. Chantal Hamel found that AMF seem to improve the capacity of host plants to use organic sources of P and N. She concludes that “AMF can extract soil nutrients and water efficiently, allowing good crop yields to be produced from soils with limited fertility.”

Improving soil tilth

• Keep soil covered as much as possible with living crops or crop residue Many lifeforms release substances that help soil particles stick together. Earth- • Use organic nutrient sources (green maworm ‘slime,’ root secretions (exudates), nures, composted manure) instead of fungal hyphae and bacterial filaments all synthetic fertilizers contribute to soil aggregation and tilth. • Avoid high levels of soil phosphorus Also, tunnels created by burrowing organisms allow water (and air) to penetrate • Avoid the use of pesticides, including insecticides, biopesticides and herbicides the soil. University of Manitoba’s Dr. Martin Entz CONTROLLING PESTS has been involved in several OSC research activities, including investigating the longAn abundant and diverse community of term impact of organic field crop rotations soil organisms provides strong protection on soil health. He found that crop rotations against pests that may cause root disease. that include perennial (forage) crops imIn soil with high biodiversity, beneficial prove soil health by increasing the size and microorganisms are much more common activity of soil microbial populations. When than harmful ones and can suppress dis- forage or perennial green manure crops ease-causing (pathogenic) organisms. are grown, there is a thorough groundcover for all seasons and the soil is not disturbed PROTECTING SOIL LIFE by tillage or cultivation.

When roots access more nutrients, the result can be healthier food. For example, in one study, OSC scientist Dr. Miranda Hart found that AMF-inoculated tomato plants had fruit with higher antioxidant capacity, higher nutrient quality and Many common agricultural practices, more carotenoids. such as tillage and the use of pesticides and synthetic fertilizers, can harm soil orCarbon sequestration ganisms. Fortunately, farmers can nourish As we face the climate crisis, research- and protect soil life by following many baers are investigating how carbon can be sic organic practices including: stored in the soil. Carbon sequestration is • Use a diverse crop rotation including pea complex, dynamic process in which soil rennial crops or cover crops life capture and transform carbon. • Avoid or minimize tillage

Tillage can injure soil invertebrates and damage their habitat by destroying tunnels and soil aggregates, which then reduces the infiltration of water and air into the soil. Microorganisms can also be affected. Entz found that tillage can decrease AM colonization and disrupt fungal networks. However, Dr. Chantal Hamel found that soil microorganisms were more affected by the removal of crop residue than tillage. Hamel has been involved in various OSC

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

activities with a focus on AMF. While crop residue is a clearly visible food source for soil life, another food source is crop roots, which nourish soil organisms during the growing season and after harvest. Removal of crop residue can be more disruptive than tillage because ground cover (crop residue, mulch or plants) provides habitat and moderates soil moisture and temperature. This is important because many soil organisms, particularly AMF, are sensitive to dryness, waterlogged soil and temperature extremes. Cover crops can provide ground cover in gaps in the crop rotation and between crop rows. At the Summerland Research and Development Center, UBC’s Dr. Miranda Hart has investigated the impact of cover crops on soil life in vineyards, and the impact of AMF inoculations on grapes. Her team concluded that cover crops have many beneficial effects on soil life. In particular, they found that: (1) increasing plant diversity (including cover crops and weeds) increases soil microbial diversity and inhibits soilborne pathogens; (2) growing a diverse range of plants (e.g., legumes, brassicas, other broadleaf plants and warm-season and cool-season grasses) can increase populations of beneficial microbes; (3) brassicas (e.g., radish and mustard) suppress fungal disease and promote bacteria that also suppress disease (white mustard, in particular, led to reductions in necrotic root damage and abundance of the pathogen, Ilyonectria);

Cover crops provide food for soil life and protect their habitat in many ways, including moderating soil temperature and reducing the risk of erosion. (Photo by Janet Wallace)

mustard or radish won’t help the fungi. For the same reason, crop rotations with frequent use of brassicas are not conducive to strong AMF populations. However, inter(4) using native plants as cover crops cropping with non-brassicas or following may promote beneficial soil microbiota, brassicas with legumes or grass/cereal including the beneficial fungi Beauveria green manure can help. bassiana, and inhibit pathogens; and (5) “frequent tillage, herbicide use and copper fungicides can harm populations of beneficial microbes.” Martin Entz also found that keeping the soil covered in the winter with cover crops can increase AMF colonization. Brassicas, however, don’t host AMF so cover crops like

CHOOSE ORGANIC FERTILIZERS

Carbon from decomposing plant or animal matter provides energy for soil microorganisms. Synthetic N and P fertilizers do not contain carbon and consequently they just feed the plant, not the soil.

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

The choice of organic soil amendment affects soil life. Composted cow manure may contribute more to soil life than pelletized chicken manure. In OSC2, Dr. Caroline Côté investigated the effect of crop rotation and different nutrient sources on carrot yields and soil life. The study involved green manures (pea, oat, control) and organic fertilizers (poultry manure pellets, composted cow manure, control). Of these nine scenarios, bacterial richness was greatest in the pea-compost and oat-compost plots. For larger life forms including beneficial fungi, species richness was greater when composted cow manure was applied, compared to pelletized poul-

try manure. This is important not simply from an ecological perspective but also because more beneficial fungi in the soil were linked with greater carrot yields. “The effect of the long-term use of phosphorus fertilizer, including rock phosphate, on soil life has been studied in various OSC activities with conflicting results. Differing P availability in the soil seems to change the composition and function of microbial communities. Dr. Hamel found that the predominant species of soil bacteria and fungi shifted due to long-term phosphorus fertilization on alfalfa fields. In another study, P fertilizer use on soybean and wheat fields negatively affected AMF diversity and/or abundance.

INOCULATION

Earthworms are great indicators of soil health. (Photo by Janet Wallace)

Growers can inoculate soil, or plant seeds or roots with beneficial organisms. Inoculating legume seed with Rhizobia is a common practice. AMF inoculation is less common and more complicated, even controversial. Chantal Hamel found the efficacy of AMF inoculants depends on matching the appropriate strain to soil properties. In addition, the AMF already in the soil affects the degree to which the inoculant colonizes crop roots. Miranda Hart, however, is concerned that commercial AMF inoculants may threaten local AMF communities. She asserts that “based on the available data, we conclude that the current practice of AMF inoculation is at best a gamble, and at worst an ecological threat.”

FOR MORE INFORMATION Farming with Soil Life: A Handbook for Supporting Soil Invertebrates and Soil Health on Farms. https://xerces. org/sites/default/files/publications/19-051.pdf

Root nodules. (Photo by Janet Wallace)

Tales From The Underground: A Natural History Of Subterranean Life by David W. Wolfe

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Abri Végétal:Tasty Organic Crops, Grown Smartly JOA NNIE D ’A MOUR S P H D S T U D E N T, L AVA L U NI V E R S I T Y

Annie Lévesque of Abri Végétal at the farmers market in Compton, QC. (Submitted photo)

Organic greenhouse operators want to optimize use of light, energy and natural resources for four-season vegetable production. The goal is to reduce the ecological footprint, enhance food security, and improve farm sustainability and profitability. Frédéric Jobin-Lawler and Annie Lévesque, owners of Abri Végétal, support this approach by participating in research led by Martine Dorais, a professor at Laval University, who is comparing vertical organic agriculture to the intelligent use of greenhouses as part of Organic Science (OSC) Cluster 3.

tion of microgreens in growth chambers; the efficiency and cost-effectiveness of 2) intra-canopy cultivation; and 3) effect the different systems. LEDs reduced enof biostimulants. ergy consumption and heat emission. For The producers sow various crops (Swiss microgreens, LED use in growth chambers chard, pak choi, mustard, shiso, amaranth, is ideal because the temperature produced etc.), which are harvested after 21 days by HPS fixtures is unsustainable for the and combined to create a microgreen plants.

mix. Before the OSC project, the quality of their product was highly dependent on the quality of the potting soil. They want to optimize their production methods to ensure the quality of their product, while adding flavour and nutritional qualities not achievable in hydroponic systems. They are Abri végétal is a family farm in Comp- evaluating the impact of light, fertilizer and ton, Québec’s Eastern Townships, which inoculant types on the microgreens. produces organic greenhouse vegetables During the first part of the project in (tomatoes, cucumbers, etc.), herbs and mi- growth chambers, light-emitting diode crogreens. Their products are sold locally (LED) lights were tested with different light and exported to the US. The owners aim to spectrum and different photoperiods: reduce their carbon footprint, while adapt- long days and short nights (20 hours (h) ing to new market conditions (crop diversisunlight, 4h darkness); fication, increase in the length of growing season) and support scientific research. - short days and very short nights (5h sun and 1h darkness alternating over 24 hours); Complementing the laboratory tests

Frédéric looks forward to optimizing their methods of producing microgreens in growth chambers. "I will have a lot of knowledge about the effects of photoperiods and the impact of the light spectrum. I will be able to apply this knowledge afterwards". In the second part of the research, Abri Végétal sought to optimize the 3000m2 of greenhouses by improving the yield per square meter. Instead of the usual gap between two crops, they overlapped crop spacing of different crops. Growing two crops is cost-effective because it increases the yield/m2.

They transplanted cucumber seedlings at the base of tomato plants that were nearing the end of their life. Timing of conducted at Laval University, Abri - control: natural sunlight supplemented transplanting was chosen to give the young Végétal is a real-life test site for three by high pressure sodium (HPS) lights. crop adequate light. The growers reduced aspects of the OSC research: 1) producThese comparisons aimed to determine the foliage of the old crop in favour of the

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

young crop, and placed lights inside the tomato canopy to give the seedlings sufficient light. Frédéric has gained expertise by helping with the experimental setup. He now wants to add lights throughout the greenhouses. Since diseases are favoured by continuous cultivation, different inoculum treatments (bio-suppressants) will be tested during the third part of the research activity. The bio-suppressants could limit the establishment of certain pathogens, such as Pythium. The treatments will be applied by inoculating potting soil with a new treatment or by using leachate from their soil (to tap into the microflora already present). Through this research, Abri Végétal seeks, above all, to support the science; the producers know that sometimes the results do not meet expectations. "It's as important to know what works as it is to know what doesn't." At the end of a research cycle, research- Frédéric Jobin-Lawler and Annie Lévesque, the owners of the Abri vegetal. (Submitted photo) ers summarize and disseminate the results of the entire project to the various partners. Frédéric appreciates these presentations: "It allows us to have information quickly on what has happened elsewhere and it directs us towards new avenues of testing to be done at home.” The greenhouse growers at Abri Végétal have a clear vision of the future of organic soil-based agriculture: "We have always believed in the principle of organic certification, that a plant should grow in the soil”. They want to offer consumers organic products that stand out for their terroir flavour, in addition to being products without synthetic pesticides. By collaborating with OSC research, they hope to demonstrate that the soil is the best source of protection against many plant diseases. The preliminary results of the next part of the project on bio-suppressors look promising!

Frédéric Lawler-Jobin of Abri Végétal. (Submitted photo)

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Cover Crops: A Secret Weapon For Healthy Soil? S T ÉP H A NIE L AV ER GNE 1 A ND JOA NNIE D ’A MOUR S 2 1

P H D S T U D E N T, D A L H O U S IE U NI V E R S I T Y, 2 M . S C . S T U D E N T, U NI V E R S I T É L AVA L ,

Cover crop mixtures planted after cereal harvest in 2020. (Photo by Stéphanie Lavergne)

Certified organic farming uses many approaches to farm management but those that require intensive tillage practices for weed control are unacceptable under organic. Intense tillage can alter soil physical and biological properties, deteriorating the health of the soil. So what can be done? Cover cropping might be the answer. Cover cropping could mitigate the effect of intensive tillage by enhancing soil health. Cover crops are non-commercial crops often grown as full-season crops, fall-seeded crops or intercrops. They are primarily used to promote soil health, by improving biodiversity and soil tilth and reducing erosion, but can also smother weeds, support pollinators and reduce pest pressure.

SOIL HEALTH Soil health can be defined as the capacity of a soil ecosystem to provide its vital functions. These include: support plant growth, provide habitats for various organisms, mitigate climate change, regulate flooding, sequester carbon, etc. Soil is the foundation of most agricultural production and are particularly important in organic farming, as crop nutrition mainly relies on the activity of soil organisms (soil food web) in these systems.

Organic farmers are especially interested in the biological health of their soil, as revealed by Dr. Derek Lynch and Ms. Carolyn Mann’s recent study on farmers’ perception about soil health in Atlantic Canada. Similar to assessments of human health, soil health is measured using a combination of tests. While some of these physical, chemical and biological tests can be done directly in the field, lab-based soil health tests are done on soil samples that are representative of a field. Soil tests can broadly evaluate the overall soil health at the farm level, or specifically assess an agronomic approach or problem of a certain field.

tent of pea-based cover crop mixtures to evaluate their effect on available soil nitrogen and corn yield in the following year. The field study was conducted in Québec at a research site and on-farm in collaboration with an organic grain corn producer. Three cover crop mixtures containing field peas were compared to pure stands of field pea.

The study revealed that, on average, the cover crop roots accounted for only 14 percent of the total nitrogen content of the cover crops. The pea-based mixtures had a lower shoot biomass, but a higher root biomass than the pure stand of field pea. Corn yield following a pure stand of pea or pea-based mixtures was improved by 28 percent compared to a control without a COVER CROPS SUPPLY NITRO- cover crop. Thus, pea-based mixtures are GEN TO ORGANIC GRAIN CORN a good alternative to a pure stand of pea to supply nitrogen for corn as they would Cover crops are often fall-seeded by further enhance soil health and ecosystem Canadian organic growers to provide soil services with their greater root biomass. cover during winter (and preventing nuDigging into the scientific literature, the trient losses and soil erosion) and provide nitrogen for the following crop. Producers researchers also highlighted that legume were curious to know if fall-seeded cover and legume-based cover crop mixtures are crop mixtures could perform better than best suited to increase the soil levels of nifall-seeded pure stands of field pea (cv. trogen and carbon content and to improve 4010). A team of researchers at Université yields, while non-legumes are best suited Laval and Agriculture and Agri-Food Cana- to reduce soil residual nitrogen and control da measured shoot and root nitrogen con- weeds. When choosing a fall-seeded cover

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

crop, farmers should consider mixtures of legume and non-legume species since they offer a good trade-off among agronomic benefits and soil and ecosystem services.

Table 1. Summary of the results from the cover crop mixtures study.

SOIL HEALTH IN ORGANIC TILLAGE-BASED SYSTEMS Although using cover crops can increase cash crop yields, recent on-farm studies have shown that diversified rotations including cover crops are associated with increased tillage intensity and a negative effect on soil health. Federal and provincial governments are setting ambitious targets in soil conservation to improve both soil health and soil carbon. Understanding how field management practices and combined approaches influence soil health and soil carbon dynamics is a key research gap.

1 2

Treatment

Legume proportion (%) of cover crop

Shoot biomass (t/ha) 1

Soil mineral nitrogen (kg N/ha)

Corn yield (t/ha) 2

Control

4.0

Pure stand of pea

100

19.5

5.6

2-species mixture

19.7

5.3

6-species mixture

19.4

4.4

12-species mixture

20.3

5.2

https://www.sciencedirect.com/science/article/pii/S0167880921003613 https://acsess.onlinelibrary.wiley.com/doi/10.1002/agj2.20727

PhD student Stéphanie Lavergne (Dalhousie University), Dr. Derek Lynch (Dalhousie University) and Dr. Caroline Halde (Université Laval) are collaborating with 11 organic farmers in Québec to address this research gap. An on-farm soil survey is being conducted to determine how specific management practices affect soil health indicators and earthworm population dynamics. Earthworms are particularly valuable indicators when it comes to soil health, as they contribute to soil carbon dynamics, and are sensitive to cropping and tillage practices. Organic farmers are curious to know: How does soil health vary across their farm? Which soil health indicators are influenced by their management practices? Which soil health functions should they promote and how can they assess them? Preliminary research completed on Québec organic grain farms suggests that earthworm abundance and species diversity were influenced by soil organic matter concentrations and management practices, such as tillage intensity and crop rotations. More concretely, earthworm total abundance decreased with tillage frequency – more tillage led to fewer earthworms.

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

A Québec producer participating in the project was surprised by the abundance of earthworms in his fields in 2019. This producer adopted reduced tillage practices several years ago and is glad that this has had a real positive effect on his farm’s soil health. This study is still ongoing as of fall 2021. More findings on how soil health and carbon dynamics are influenced by management practices should be available soon.

CONCLUSION Cover crops in pure stands and mixtures have the potential to provide many ecological services, such as weed control, nitrogen supply, improved crop yield and soil health benefits. More knowledge on the contribution of different cover crop species in terms of shoot/root biomass and carbon and nitrogen content would help producers choose cover crops (or mixtures) that Earthworm in a harvested soybean field. (Photo by Stéphanie Lavergne) best suits their needs. Moreover, future research should clearly identify the mechanisms underlying soil nitrogen mineralization, carbon stabilization and soil health benefits from cover crops across different cropping systems. This will help farmers and stakeholders adapt their practices to enhance organic crop yields while maintaining soil health.

FOR MORE INFORMATION To learn more about OSC3 Activity 27, please visit dal.ca/oacc/osciii For more results on green manure systems in Eastern Canada, please visit www.dal.ca/oacc/bulletins

Student hand sorting earthworms in the field. (Photo by Stéphanie Lavergne)

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Research team standing by the corn ready to be harvested during the last field day of the project. (Photo by Pascal Tessier)

Students from Université Laval sampling cover crop aboveground biomass before winter kill in October 2017. (Photo by Caroline Halde)

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

The More The Better? Multi-Species Vs Single-Species Cover Crops For Carrots F R A NK L A R NE Y 1 , H A L E Y C AT TON 1 , CH A R L E S GEDDE S 1 , NE W TON LUP WAY I 1 , TOM F OR GE 2 , R E Y N A L D L EMK E 3 , A ND B OBBI HEL GA S ON 4

The control cover crop treatment which was essentially a fallow predominated by lamb’s quarters, cleavers, and redroot pigweed, July 30, 2018. Maybe weeds are not all that bad? ...as long as they don’t go to seed before soil incorporation. (Photo by Frank Larney)

Our research team collaborated with Howard and Cornelius Leffers who run an irrigated organic farm near Coaldale, Alberta. They specialize in carrots and red beets for restaurants, farmers’ markets and orIn recent years, diverse cover crop mix- ganic grocery stores, and they also grow es or ‘cocktails’, which contain as many alfalfa, winter wheat and dry beans. as 15 different cover crop species, have We evaluated seven cover crop treatgained popularity. Are these multi-species ments ahead of carrots. We have completcover crop mixes any better than their less ed two cycles of the two year cover crop– sophisticated counterparts (e.g., fall rye or carrot rotation (Cycle 1: 2018 & 2019, Cycle barley/pea)? It’s a complicated system to 2: 2019 & 2020), with a third cycle (2021 untangle. Our early data suggests that the & 2022) currently underway. Cover crops multi-species mixes can foster more active were established in June during the first soil life, but that they could also have im- year of each cycle as follows: pacts on the following crop: they caused 1. Buckwheat; more forked carrots, which decreases profit. We also looked closely at how weeds 2. Faba bean; Agriculture & Agri-Food Canada; 1 Lethbridge, AB; 2 Summerland, BC; 3 Saskatoon, SK; 4 Dept. of Soil Science, Univ. of Saskatchewan

in the cover crops affected soil fertility. 3. Brassica (white + brown mustard); Spoiler alert, they may be helping... 4. Mix*; Cover crops can provide many benefits 5. Mix* followed by barley which grew until including enhanced soil organic matter and the first killing frost; soil health, nitrogen retention, weed suppression, soil moisture conservation and, 6. Mix* followed by winter wheat which survived the winter, regrew in early spring, as a result of these, higher subsequent then was terminated by tillage; and crop yields. Cover crops can be grown in the main season (replacing a cash crop in rotation) or seeded in fall to protect the soil from wind and water erosion throughout winter and early spring. In our study funded by the Organic Science Cluster, we compared how different cover crops impacted the soil, pests, and the following crop.

In August, all treatments and the control were incorporated into the soil by disking. The control and treatments 1-4 were left unplanted over the winter; weeds were allowed to grow. Treatments 5 and 6 were seeded to other cover crops. In the second year of each cycle, carrots were planted in June and harvested in the fall. We took cover crop and weed biomass samples just before disking in August of the first year of each cycle. We measured the carbon (C) and nitrogen (N) concentrations of the cover crops, as well as the main weed species. In 2018, the multi-species, brassica, and buckwheat cover crops were more competitive with weeds. The faba bean cover crop was not competitive with weeds and had the same amount of weeds (by weight) as the control treatment.

Weeds can be a troublesome part of organic systems. In this case, we wanted to see if they were redeeming themselves as part of the cover crop, or in the case of the control treatment, by taking the place of a seeded cover crop. Weeds are no different from any other plant: they take up soil nu7. Control (no cover crop, weeds allowed to trients and when they break down, they put carbon (including organic matter), nitrogen, grow). *Mixture of five legumes, four grasses, two brassicas, flax, and other nutrients back into the soil. As phacelia, safflower, and buckwheat (15 species in total) long as annual weeds don’t go to seed, maybe they are making a useful contribution to soil health, similar to a seeded cover crop.

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Left to right: Charles Geddes (Weed Ecology & Cropping Systems, AAFC-Lethbridge); Howard Leffers (farmer-collaborator, Coaldale, AB); and James Hawkins (visiting Nuffield scholar, Neuarpurr, Victoria, Australia) in the 15-species cover crop, August 7, 2018. (Photo by Frank Larney)

Since weeds were incorporated into the soil in August along with the seeded cover, the less-competitive faba bean treatment and the weedy control actually returned more total carbon to the soil (average, 2220 kg/ha C) due to greater weed biomass (weed “yield”) than buckwheat, brassica or the multi-species mixture (850–1330 kg/ ha C). Moreover, being a nitrogen-fixing legume, the faba bean cover crop (including its weeds) returned the most nitrogen to microbial mass - and permanganate oxithe soil at 99 kg/ha N. dizable C – the active or easily-decomposAfter the carrot harvest, our team rated able C). However, a possible downside of carrots into Grade A (visually appealing with the multi-species mix showed up when we no deformities: ideal for restaurants, farm- looked at the following carrot crop. In 2019, ers’ markets, and organic grocery stores) treatments 4, 5 and 6 resulted in a greater and Grade B (downgraded due to wireworm proportion of the Grade B category, includdamage, forking, scarring or misshaping: ing forked carrots. Forking and misshaping suitable for juicing only). Grade B car- are caused by many reasons, including soil rots are worth about one third of Grade compaction, weed interference, and insect A carrots. or nematode feeding on root growing tips.

Weeds are no different from any other plant: they take up soil nutrients and when they break down, they put carbon, nitrogen, and other nutrients back into the soil.

Despite the differences we measured in the C and N contributions of the cover crops and the weeds, it wasn’t enough to affect the carrot yields. In 2019, Grade A carrot yield was statistically the same with all the cover crop options. For soil health, the multi-species mixture had more microbial activity than either brassica or buckwheat cover crops (this is based on microbial biomass C – an index of

We also looked at the value of fall-seeded cover crops (Treatments 5 and 6) and their impact on wireworm and nematodes. These pests might actually be helped by cover crops; they appear to have greater survival during the winter season when living roots are present. But having winter cover may lead to better carrot yields, too: in 2020, total carrot yields (Grades A and B) were 10 percent higher after the fall-seed-

ed cover crops when compared to the spring-seeded brassica cover crop, which led to the lowest yielding carrots. So far, we haven’t seen any effect of the different cover crop treatments on root lesion nematode populations, but the fall-season cover crops led to a small increase in wireworm damage on the carrots (this only showed up in 2019).

More soil analyses and the results from the 2021-22 season are still to come. The additional information will help us tease out the pros and cons of multi-species vs single-species cover crops for irrigated organic carrots.

FOR MORE INFORMATION To learn more about OSC3 Activity 8, please visit dal.ca/oacc/osciii

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

Economics vs the Environment: Trade-offs in Nutrient Management for Organic Vegetables SE A N SMUK L ER FA C U LT Y O F L A ND A ND F O O D S Y S T E M S , U NI V E R S I T Y O F B R I T I S H C O L U M B I A

Economic and environmental goals: can organic farmers tick both boxes when it comes to nutrient management? Undersupply of nutrients can result in reduced crop yields and income. Nutrient management is one of the primary reasons that organic farms, particularly those producing vegetables, have lower yields than non-organic farms. At the same time, applying nitrogen

There's a lot more to consider than simply adding compost to vegetable beds each year. It's important to know how much N and P are required (how much the crop will remove from the soil) and how much N and P an amendment contains. We devised a promising strategy (Low Compost + N) that allows farmers to balance good yields with environmental stewardship.

THE COMPLEXITY OF THE PROBLEM There is often a mismatch between the ratio of N to P that the crop requires and the ratio in compost or manure. For example, the ideal ratio of N to P needed for potatoes is 6.1 and 7.6 for spinach, while the ratio supplied from manures may be as low as 1.3, and 0.6 for compost. The result of this mismatch is that, over time, farmers applying compost or manure to meet the crop’s N needs will be building up soil P, which, could eventually exceed environmentally safe levels.

(N) or phosphorus (P) above what the crop can use can result in nutrient leaching and runoff into water resources, contribute to poor air quality and emit climate-changing greenhouse gases. Managing this trade-off is difficult given that outcomes can vary To further this challenge, the rate at widely with the types of amendments orwhich the total amount of the N found in ganic farmers have access to, their climate amendments mineralizes to plant-available and soil conditions. N can vary widely. For example, laboratory incubations of composted poultry manure have shown that the amount of the total N that is mineralized over a season can range from 3 percent to 37 percent.

Mineralization rates are largely determined by the carbon to N ratio of the amendment but also the soil type, temperature and moisture. Accurately matching the supply of nutrients to the crop needs therefore requires not only knowing how much plant-available N and P is contained in the amendments, but also an estimate of how much is likely to be mineralized during the production season. With this information, farmers can use permitted fertilizers to make up for any imbalance in the N to P ratio.

Plot establishment at Greenfire farm on Vancouver Island, British Columbia (Submitted photo)

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

Ideally, much of the N and P applied to a field would be cycled on-site using nutrient-scavenging cover crops over the winter. N could also be added to the system through N-fixing cover crops (rather than

by adding amendments). In BC, however, Table 1. Four nutrient management strategy treatments repeated in 2018 and 2019. effective cover cropping is difficult. There is a short window of time for farmers to get Treatment Description them established, the cool winters limit N fixation and biomass production, and the High Compost Compost applied at a rate targeting crop N needs (removal) migrating waterfowl can completely devour cover crops. Finally, the cost of compost, manure and organic fertilizers varies widely across the province depending on their regional availability. This multitude of factors means that effectively addressing nutrient management trade-offs is a complex task and the best solutions will vary widely by region.

Low Compost+N

Compost applied at a rate targeting crop P removal + feather meal N to match crop N removal

Typical

Compost and/or fertilizer applied using the farm's typical approach

Control

No compost applied

MEASURING TRADE-OFFS THROUGH CONTROLLED EXPERIMENTS To investigate the economic and environmental outcomes of nutrient management strategies on organic vegetable farms in BC, the Sustainable Agricultural Landscapes Lab at University of British Columbia (UBC) launched a study with the support of the Organic Science Cluster 3 in 2018. Post-doctoral fellow Dr. Kira Borden led the establishment of a controlled experiment on two working farms (“mother farms”) with distinct management histories and soils. The UBC Farm in the Fraser Valley is on coarse-textured soils and Greenfire Farm on Vancouver Island on fine-textured soils. At each site, four treatments were established in replicated plots (Table 1). Potatoes were grown in the first year and cabbage and cauliflower in the second year. There were larger yield gains (yield compared to control) for potatoes under High Compost compared to Low Compost+N, but no differences between nutrient management strategies for the brassicas. Potato yield gains were more pronounced at Greenfire Farm than at UBC Farm. We also consistently observed more efficient use of N with Low Compost+N, which resulted in about 20-100 percent of applied N being recovered (taken up) by the crops, while less than 20 percent of N was recovered in the High Compost plots. This trend

Daughter farm site in Pemberton Valley. (Submitted photo)

was mirrored for P recovery but with some mate conditions and costs of nutrients, we established field trials on 20 mixed vegecrop-specific exceptions at UBC Farm. table farms (“daughter farms”) across three EVALUATING THE TRADE-OFFS regions of southwest BC. These trials were led by Master’s student Amy Norgaard. IN DIFFERENT REGIONS At the daughter farms, we compared the To evaluate how economic and envi- same treatments as at the mother farms ronmental trade-offs of different nutrient (Table 1) but without a control, which could management strategies vary by soils, cli- have led to lower yields for the farmers.

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

We found no consistent differences in yields when all three regions were taken into account. The exception was in the second year, in the Fraser Valley (a region characterized by inexpensive, high-nutrient content composts and soils high in P), we observed greater yields in High Compost than Typical. We also found no consistent differences in input costs except for the Fraser Valley where Typical was the lowest. Overall, we observed 21 percent higher levels of P left behind in the soil with High Compost than Low Compost+N. We also found that High Compost resulted in elevated soil nitrate levels after the crop was harvested at farms using high-N compost (sampled 0-30 cm deep in the soil). These extra nutrients left behind in the soil could be cause for environmental concern if there is no cover crop planted to recover them.

CONCLUSIONS AND NEXT STEPS Results from our mother farm trials clearly showed more efficient use of nutrients with Low Compost+N. Using this approach can minimize the trade-offs between economic and environmental objectives. Results from the daughter farms were similar, but our findings were less definitive because of variability among the different regions and in the farm management. The daughter farm analysis confirmed that ineffective nutrient management results in increased environmental risk (due to potential nutrient loss), but also that many organic farmers in BC are already managing these trade-offs effectively. The detailed economic analysis we have underway will help to evaluate these potential trade-offs. An important caveat: the nutrient management strategies that we used are expected to slowly change soil properties such as P and organic matter. It will be important for future research to assess the long-term impacts of these strategies. Postdoctoral Fellow Dr. Kira Borden harvesting at the UBC Farm experiment plots. (Submitted photo)

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2

S P R I N G 2 0 2 2 , I S S U E # 4, O R G A NI C S C IE N C E C A N A D A

O R G A NI C S C IE N C E C A N A D A , I S S U E # 4 , S P R I N G 2 0 2 2