Effects of wood-based compost on soil health and fungal populations in an organic loam

Sabrina Anderson*

Objective

Determine whether wood compost enhances soil microbial life (specifically Trichoderma spp.) and promotes healthy plant growth

Central hypothesis

Wood compost application will increase Trichoderma spp. frequency, active carbon, microbial soil respiration and plant biomass when compared with an organic compost or control

Methods

Experimental Design

• Completely randomized design with three treatment and 10 replicates
• Each experimental unit was a 4" pot of soil from an organic vegetable farm (Friesen Farms, Langley, BC) planted with a single lettuce transplant (cv. 'Hampton')

Randomization scheme (left) and experimental setup

Treatments

1. Organic compost: soil amended with 25% (volume basis) commercial yard waste compost (Boost Class A Organic, Net Zero Waste, Abbotsford, BC)
2. Wood compost: Soil amended with 25% (volume basis) wood-based compost (Equal proportions of 5-10 mm wood shavings and grass clippings composted underground for 45 days)
3. Control: No soil amendment

Study Location and Sampling

• Initial subsample of the bulk soil was analyzed for active carbon (5), soil respiration (5), and CFU counts (7) using Trichoderma specific agar (2) at the KPU Institute for Sustainable Horticulture (ISH) Lab in Langley, B.C. 
• Two week-old lettuce plants were transplanted into the experimental pots on May 30th and grown until July 17th in a passive solar greenhouse (KPU Research & Teaching Farm Dome, Garden City Lands, Richmond, B.C.) 
• Plants were evenly watered, photographed and monitored for signs of stress throughout the growing period. Notes and photographic records were kept weekly.
• Plants were removed from soil after seven weeks, washed, divided into roots and shoots, oven-dried for ~48 h, and weighed to determine dry-weight biomass (KPU Seed and Soil Lab, Richmond, BC)
• Rhizosphere soil samples were air-dried and analyzed for soil respiration (5), active carbon (5), and CFU counts (7) using Trichoderma specific agar (KPU ISH Lab, Langley, BC)

Passive solar dome greenhouse at the KPU Research and Teaching Farm on the Garden City Lands in Richmond, BC

Statistical Analysis

Data were tested for normality using the Shapiro-Wilk test. ANOVA was used to test for treatment effects. Means were separated by Tukey’s Honest Significant Difference Test. All analysis employed the jamovi interface (8) for the R statistical computing environment (6), with alpha = 0.05 maintained throughout. 

Results and Discussion

Active Carbon

More active carbon was found in the two treatments amended with compost than in the unamended soil or the bulk soil sample (Fig. 1). Active carbon served as an indicator of the readily available food and energy sources for the microbial community in the soil. It has been correlated with particulate organic matter, organic matter, aggregate stability, and respiration (3). Because active carbon was not higher in the control treatment than in the bulk soil sample, the increase in active carbon was attributed to the compost amendment rather than the lettuce.

Fig. 1. Active carbon in soil treated with different soil amendments (control, wood compost, and commercial organic compost). Error bars denote standard error of the mean (n=10). Means labeled with the same letter do not differ significantly (alpha=0.05).

Soil Respiration

Soil respiration was higher in the compost treatments than in the untreated control or bulk soil sample, and higher in the wood compost treatment than in the organic compost treatment (Fig. 2). Soil respiration has been positively correlated with active carbon. It indicates soil microbial activity associated with organic matter decomposition, an essential part of soil nutrient cycling that supports plant growth.  Differences in soil respiration could be attributed to the compost inputs rather than the lettuce transplants.

Fig. 2. Respiration in soil treated with different soil amendments (control, wood compost, and commercial organic compost). Error bars denote standard error of the mean (n=10). Means labeled with the same letter do not differ significantly (alpha=0.05).

The wood compost likely had a higher C:N ratio than the organic compost, resulting in slower initial decomposition. Short-term impacts could include nitrogen demobilization, while long-term benefits might include higher water holding capacity and reduced susceptibility to erosion. In the long term, inputs of carbon-rich materials improve soil fertility and quality. The organic compost likely had a more balanced C:N ratio, resulting in an earlier increase in fertility with longer-term benefits to soil structure.

Soil Fungi

The wood-based compost had more soil fungi than the other treatments (Fig. 3). Trichoderma was not detected among the fungi.

Fig. 3. Fungal colony forming unit (CFU) counts from soil treated with different soil amendments (control, wood compost, and commercial organic compost). Error bars denote standard error of the mean (n=10). Means labeled with the same letter do not differ significantly (alpha=0.05).

Lettuce Biomass

Dry weight of lettuce shoots was higher in the commercial compost treatment and lower in the wood compost treatment than in the control (Fig. 4). Despite its potential benefits to the soil microbial populations, the wood-based compost inhibited plant growth in the short term, perhaps due to N-immobilization.

Fig. 4. Dry weight of lettuce shoots grown in soil treated with different soil amendments (control, wood compost, and commercial organic compost). Error bars denote standard error of the mean (n=10). Means labeled with the same letter do not differ significantly (alpha=0.05).

Plants in the wood compost and control treatments exhibited chlorosis on their outer leaves during the first four weeks after transplanting, suggesting N deficiency. In the final three weeks of the trial, plants in wood compost treatment recovered from chlorosis but the larger plants in the commercial compost treatment exhibited stress symptoms (bolting and necrosis) suggesting they were becoming pot-bound.

Conclusions

• Wood-based compost increased active soil carbon, soil respiration, and soil fungal populations. Trichoderma was not detected among the fungal colonies. 
• Although the slow decomposition of the high-lignin wood-based compost results in short-term N immobilization, it could still offer long-term benefits. Additional N inputs may be necessary when using wood-based compost.
• A commercial compost increased active soil carbon and supported faster lettuce growth than the wood-based compost.

*Department of Sustainable Agriculture & Food Systems, Kwantlen Polytechnic University

email sabrina.anderson <at> email.kpu.ca

Acknowledgments:

Special thank you to Dr. Deborah Henderson, Director of the Institute for Sustainable Horticulture, for opening up their lab to complete my research and for suggesting research on Trichoderma. Matilda Tabert, Research Technician, assisted with lab analysis. Net Zero Waste donated organic compost for the trial. Thank you to Andy Smith, KPU Research and Teaching Farm Manager and the rest of the farm team for watering the trial.

References

1. Adnan, M., W. Islam, A. Shabbir, K.A. Khan, H.A. Ghramh, Z. Huang, H.Y. Chen, and G. Lu. 2019. Plant defence against fungal pathogens by antagonistic fungi with Trichoderma in focus. Microbial Pathogenesis 129:7–18.
2. Elad, Y., I. Chet, Y. Henis. 1981. A selective medium for improving quantitative isolation of Trichoderma spp. from soil. Phytoparasitica 9:59-67.
3. Launchbaugh, K. 2009. Direct measures of biomass. University of Idaho College of Natural Resources. https://www.webpages.uidaho.edu/veg_measure/index.htm
4. Lenth, R. (2018). emmeans: Estimated Marginal Means, aka Least-Squares Means. [R package]. Retrieved from https://cran.r-project.org/package=emmeans.
5. Moebius-Clune, B.N., D.J., Moebius-Clune, R.R., Schindelbeck, K.S. Kurtz and H.M. van Es. 2016. Cornell University Comprehensive Assessment of Soil Health Laboratory Standard Operating Procedures. bit.ly/SoilHealthSOPs. P42-56
6. R Core Team (2018). R: A Language and environment for statistical computing. [Computer software]. Retrieved from https://cran.r-project.org/.
7. Tabert, M. (n.d) Soil dilution plating: protocol 2.21. Institute for Sustainable Horticulture.
8. The jamovi project (2019). jamovi. (Version 1.0) [Computer Software]. Retrieved from https://www.jamovi.org.

Terrace Walk and Lab Time! ~ November 21st

November 21st was a brisk morning with temperatures ranging from 3-12 degrees Celsius and rain spattering throughout the day. We started off our morning taking a walk through the terraces and looking at the preparations that had been made for the end of the season.

 As you can see, all of the plants are gone! Everything has been pulled up except for the, the irrigation lines have been removed and the perennials are dying back as they slowly transfer their energy from their shoots to their roots for the winter. pulling out the dead material Soon it will be time to put hay over the perennials to prevent frost damage so they will be ready to grow come spring. Of course having bare soil all winter long is not a good idea, so Torin has seeded the terraces with a winter cover crop! Cover cropping this area is an excellent idea because it is such a new area to farming, the cover crop will lock nutrients into the soil that other wise may leech out over the winter, and will provide a structure to the soil that will keep it from blowing away in harsh winds or breaking down over time. This year we are using a combination of crimson clover, a rye, and a vetch in order to fix nitrogen, create a hefty mulch for the spring and build up the soil structure.

As you can see in the photos above, the cover crop is just starting to peek out of the soil! it hasn't gotten too cold yet so hopefully we will see a nice cover by the time full on winter sets in!






After we walked through the terraces to check out the cover crop, we headed up to the lab for the majority of our class to talk about and work on our final projects! Our final project is all about identifying plants and bugs that are commonly found on the farm. We have spent all summer and much of our fall on the farm keeping our eyes peeled for interesting  bugs and weeds, and now it is time to put everything together! Rebecca and Mike brought us up to the lab and showed us where all of the supplies for our pinning and taping were and gave us the rest of the class to have at it!

Here you see Kirsten taping her plants to paper so that each sample is neatly displayed for examination and identification. Kirsten is also one of the students that decided to get the project done earlier rather than later and is almost done!

Here we see Lindsay and Hazel pinning their insect samples into the perfect positions so that they can dry in spread out forms that are easy to examine. Each bug must be spread out and pinned and then left to dry out in the correct position before being placed into the final shoe box that will be handed in. Lindsay is still working on the initial pinning process but hazel has already moved on to the final pin into the shoe box! This process of pinning, drying, identifying, labeling,  and pinning again takes quite a long time, but the end result can be quite impressive as we see in the finished shoe boxes of other students. 
This is the second last week of classes and even though everyone is feeling the stress of the final crunch to end of semester, we all manage to smile and laugh as we slowly work through this project. Only in agriculture so we see people smiling and laughing while surrounded by bugs.

Second-last market

Our second to last harvest. Photo: Mike Bomford

This week was the second to last harvest for the market! The harvest list included beets, carrots, potatoes, leeks, brussel sprouts, pumpkins and squash. With this being our second to last market many of us were reflecting about how quickly the season has gone by.

The class prepping the harvest for market. Photo: Mike Bomford

During our walk about today we looked at all the interesting things still happening on the farm. First, we checked out our carrot variety trial which will be harvested and saved for evaluation later on in the year. This trial is an awesome collaboration with BC Eco-Seeds comparing the growth of carrots from various seed producers.

Styrian Pumpkin. Photo: Australian Seed

We took a look at the squashes which are still in he field. The spaghetti squash will be left for a at least one week longer to ensure more shell hardening. This extra time ripening in the field will allow the squash to stay in storage longer. The Styrian squash which is an extra special variety that produces hulless seeds, perfect for pumpkin seeds that can be snacked on or used in recipes. 

We learned about how the brassica remains in the field can become an  excellent bio-fumigant which will protect the field from future pests. First, we must transfer  the remains to the compost bin will will allow for the leaves to decompose in an environment that produces heat.The heat will allow for proper decomposition making the resulting compost an excellent soil amendment. 

Nic Walser standing next to the compost pile full of brassica remains. Photo: Mike Bomford

We also spent some time learning about Stark's strawberry field trials which is comparing the growth from a control treatment which has no coverage and compares it to another treatment using a row cover and another which is using a low tunnel. The results from his research are still to come and we look forward to finding out more in his final research presentation. 

A Late Post about the Last Market

The season is done and the year will follow shortly, but what a year it’s been! The time has flown and we’ve grown along with it, experiencing much of what a full farming season entails, getting first hand experience with our boots in the dirt. We spreaded soil amendments and took samples, prepared beds both by hand and machine, seeded and transplanted, weeded and hand gathered the fruits (but mostly vegetables) of our labour.

One of the better experiences personally was the time we got to spend sharing those fruits, swapping stories and jokes with the locals who joined us for our weekly market. While the market started slow, the final months were a roaring success and the last market of the year was no exception. On the spookiest day of the year, Torin and I set up the Kwantlen booth only to have several families fawning over the diverse selection of hearty fall vegetables before the market had officially begun. A rainbow of beets, mountains of butternut, acorn and spaghetti squash, bundles of leeks and carrots, potatoes, brussels sprouts, and sweet sweet sorghum awaited purchase, and the day did not disappoint.

It was a parade of characters that day, some in costume and some not; Spiderman serenading us all with a five string guitar and Willie Nelson covers, along with some lesser known comic book characters who were only passing through, even Leeloo from The Fifth Element made a brief appearance. Dogs in costumes, cats AS costumes, along with myself dressed as a cow were spotted (subtle cow joke there), thanks Eric for lending me the costume! Torin was decked out as a farmer, classic!!... He may or may not have actually been in costume.

The day was busy, folks quickly snatched up our carrots and beets, anxious to make some hearty warm soup. Both the bulk beets and bundles were popular, the bundles for their beautiful colour and the bulk for the sweet deal. However there was no sweeter deal than the candy we were giving out, sweet sorghum that I’d been waiting to taste all summer. Some families needed a bit of coaxing to try the treat (suspecting a trick perhaps), but everyone loved it once they’d given it a chew. By the end of the day we had a couple families come back to see how much was left; we’d had more than we knew what to do with since the start and happily saw them off with a shopping bag full of the stuff, with the dad grinning more than his son. I will admit I had to demonstrate the sorghum eating technique with just about every person I gave some to, more than making up for the candy I wouldn’t gorge on that evening now that my trick or treating days were over. Sorghum is no substitute for lunch however, so I got to show off my spots in the nearby senior center’s cafeteria. It was a hit!

Now just because we were having a blast selling produce didn’t mean the learning was over! Torin’s day was about to get interesting, as he spotted an older fellow on a tricked out bicycle who wandered over to buy some beets and leeks. We’ve learned that knowing your market is crucial for every size of farm, but especially ones that sell direct to the consumer, and Torin had unknowingly just spotted a friendly and informative source of knowledge about some of the particulars of selling fresh vegetables in Richmond. This wealth of knowledge became apparent within a few minutes of conversation, and he quickly filled our heads with suggestions for traditional Asian vegetables that would be in high demand if they were produced next year, along with ideas of how to better market the more western fare to many of the market patrons. Many of the customers were with their grandchildren and are of course interested in giving those kids the support they need nutrition-wise; marketing around the health benefits for growing kids could go a long way and help the Kwantlen market continue to grow over the course of next season.

Safe to say our season ended on a high note, with a successful and busy market, along with some good laughs and free candy. I was glad I got to be apart of it! Maybe Rebecca and Mike will let me tag along outside of Agroecosystems next year, though I’ll probably leave the cow costume at home. (Just kidding Eric!)

Time to look back on the fun, because that was a seson well done.

Looking through seed catalogues

What on earth will we grow

Rotations and crop planning

We were beginning to know

The season begins

And so much to learn

How to dress ourselves for the rain

Or prevent a sunburn

Days began to get sweaty and long

The sun was strong and high

Terraces were vibrant in colour

From the pollinator garden to the matter’s dye

Buzzing bees, hungry aphids,

And warmth in the soil

Banjos strumming at the farmers’ market

And customers so loyal

The season was abundant

The season was warm

But with the blink of an eye

It takes a new form

Changing ever so slightly

Until suddenly

It’s transformed
~

The sound of geese leaving

Cold cheeks, dry hair

The plants dwindling

And all becoming bare

But the puns keep us going

When the sun is not glowing

And Eric’s music keeps us bopping

When Rebecca says “no stopping!”

And soon the kale stops growing

And cover crops we start sowing

Time to look back on the fun

Because that was a season well done.

Being with the same group of students throughout the last 3 semesters over the farming season has been such a journey. We've laughed, we've complained, we've seen all sorts of weather and felt all of the changes of the seasons. We've raised many crops together, nurtured the soil together and made so many plant puns together. We've enjoyed the fruits of our labors with watermelon slices, juicy strawberries and chewing on sweet stalks of sorghum. What a wonderful feeling, to watch the plants grow, see the earth change, and feel in tune with the rhythms of nature. Why do I feel like eating so much soup in the Fall? Is it a coincidence that everything I am harvesting in October makes for a perfect pot of soup? The earth has so much to teach and so much to share. I will never forget the feeling of going home on the skytrain after a day at the farm: carrot tops and green things exploding out of my backpack, soil under my nails, dirt probably on my face and definitely on my knees; a deep inner joy and a smile on my face, for I am a student of the Earth.

When Sustainable Agriculture students from the 2017 season were asked what there favorite memory was, here is what they had to say:

PIPER

I’d say it was ripping out spots of blackberries for the compost pile. It was one of those moments that’s horrible but cathartic. We were using loppers not the way they are intended to be used, and just hacking away. If there was any aggression you needed to get out it got out. It was a super hot day and the blackberries were scratching us but we made a game out of it all and were laughing so much, it felt like we were part of a football team or something. 

LINDSAY

When we were transplanting brassicas into the orchard last minute. There was lots of rain, we were not prepared for the muckiness and all of the mud got stuck on our boots and it was so miserably horrible that it was hilarious. One part hilarious and one part misery.


KRISTEN
My favourite part was when we were starting out. Putting all the compost down and seeing it start from the ground up.

EMMALEE

For me it was strawberry harvest and tasting all the different varieties. It was one of the first crops to be ready, and we got to eat so many when testing for the sweetness.

STARK
When we had to cut down the rye in the terraces. We had one weed whacker and as Jordan was about to use it he realized there was no gas. Meanwhile, I came in with my sheers and kept cutting, cutting and cutting and it was maybe 30 minutes before the weed whacker was up and running. I felt like manual tools had triumphed that day.

NICK

Going to the different farms to do soil samples. We were out there in the rain and Amy had her head in the dirt making dirt puns. It helped set the class dynamic a bit. It was also cool seeing different work at different farms and how the soil varied. 

MIKE

Something I will remember from this season in particular is the puns. It’s something I’ve never seen before. I will remember 2017 for the puns.

JORDAN

I’d say it was backing up the tractor successfully and easily with the trailer attached because that made me feel like a big man. But the real reason it is my favourite memory is because I thought it was going to be really difficult but then it wasn’t so bad.

HAZEL

The community. The people are really inspirational and passionate and it’s a really supportive community. And the soil puns.

WILL
Those strawberries were really great. I thought it was really cool, not only eating the strawberries but seeing how each variety dealt with pollination issues and how breeding programs can develop fruit because some turned out really great and some turned out really narly.

JESSICA

The farmers’ markets. I loved connecting with customers and sharing stories about food. It was such a treat to buy food from other vendors as well. To establish relationships with the people we buy and sell food feels like the best way to nourish ourselves.

We asked Rebecca and Rebecca said, No more Aggies Jumping on the Bed

November 7^th at the orchard the air was brisk and clean,

Aggies piled out in to the sunlight dressing to keep warm

for any alium lover that day was a garlic dream,

the neighbouring plot was all weeds were previously grew corn

but the garlic beds were ready and the students were keen

so off we went to get muddy, this we’d been warned

Measure twice and dig once, as the old saying goes

plots chosen, we planted, offset and 6 inches apart.

The biggest bulbs are the best as everyone knows

some would grow with Rye, there progress written on a chart

Research in yield, to be written in perfect prose

But for now we dig, giving last years cloves a fresh start

The work went steady with song and much laughter
We planted, point up! and double deep in its height
the little bulbs were tucked in with a good raking after
but with all that space planted, there was extra, what a sight!
so the students descended, what was plenty, soon picked over
one task done, now another to do, this is easy with such aggie might

That corn field i mentioned, what a disastrous place
and who would have crept in but the deadly night shade
but not to fear the aggies are here and we keep a good pace
forking, pulling, racking, there are beds to be made
we are hoping our effort will leave not a trace
but weeding is labour and this class has got that in spades

In the meantime, beyond the bean poles, there are beets for the harvest
the market may be over but we can still make a good sale
there is squash and potatoes, now add beets to the mess
carted through campus, their path leaving a muddy trail
the money will got to SASA to plan adventures that are best
so when each aggie grads they can tell a good tale

when the planting and harvest and clean up is done
we round up the tools and piled back into the van
it was time (we were hungry) to get out of the sun
we felt good with our work, the days labour on the land
our pockets filled with bounty, our packs now weighed a ton
Im making pickled beets! Christmas gifts for the Kenney clan

Can you guess what we are doing? Hint: facilities will be very happy

I'd say Will is done for the day wouldn't you?

Here is the recipe mama Kenney sent me to make pickle beets, Its so easy! 

1. boil beets with the skin on for about 10-15 min depending on the size
2. then cool in cold water, skins should slip off
3. combine equal parts in pot
1. water
2. sugar
3. white or apple cider vinegar
4. 1 tbsp pickling spice in tea pouch or tea bell
5. bring to a boil and add beets
6. boil for 10 minutes and pack into sterilised jars 

The pickling spice is easiest to buy in a premixed blend cause it involves about 14 different spices. I had so many beets of differing colours, so I brewed the spices for 10 minutes and then poured the brew over the beets in the jars and used the final sealing boil to cook em in. I used a whopping 7 cups of water, sugar, and vinegar to pickle all the beets I brought home and now I have 11 1/2 jars of pickled beauty. Yum!