Preparing the campus terraces for winter

Yesterday was  a cold, wet morning to spread horse manure on the campus terrace market garden.

The end of the growing season is a good time to apply raw manure in order to minimize contact with edible crops. Organic standards prohibit harvest of organic crops within 120 days of incorporating raw manure, if the edible portion of the crop comes in contact with the soil. This precaution reduces the risk of transmitting human pathogens, such as E. coli.

We removed most of the remaining crops and the irrigation lines before spreading.

We took the inedible crop biomass that we pulled from the garden to Kwantlen's green bin for composting. It was disappointing to see that some green bin users had dumped plastic bags full of organic waste in the bottom of the bin. This plastic may contaminate the compost produced from our waste, and will certainly present a challenge for the compost operation that processes it. According to Canadian composting guidelines (pdf), 500 mL of compost used for growing food crops should contain no more than one piece of plastic or other foreign matter larger than 25 mm. 

KPU's green bin is a recent and welcome addition to campus, but its proper use will require education of the campus community. 

We left a few cold-tolerant crops, such as parsnips, carrots, kale, and chard. The parsnips and carrots will be sweetest after frost, but we won't be able to harvest them until early February if we want to comply with organic standards.

The few kale plants that we left are infested with aphids, so won't be harvested. Those aphids are supporting a very strong population of aphid predators and parasitoids, including lady beetles, syrphid flies, aphid midges, and wasps. We left the kale and a bank of flowering perennials to help the beneficials survive until next year.

The plant nutrients present in manure are less stable than those in compost. To reduce nutrient loss we incorporated the manure into the soil by raking, then seeded a winter cover crop mix consisting of 40% rye, 40% wheat, and 20% crimson clover. We distributed 1.7 kg of the mix over the 288 square meters of the market garden (~60 kg/ha), then raked again to incorporate the seed.

The deep-rooted grasses will help retain nutrients leached from the manure, and the crimson clover will fix additional nitrogen from the atmosphere. The winter cover will help prevent erosion by wind and water. Next spring, the new Agroecosystems Management class will cut these cover crops and incorporate them into the soil to add organic matter and release some of the nutrients that they retain this winter. 

The garden looks bare now, but we put up a big new sign to let the campus community know that it's still active.

With almost continuous rain since yesterday, the seeds were already beginning to swell, and some radicles had emerged, when I came to work this morning. 

Final orchard harvest and manure spreading

By the end of September the students had completed the final harvest at the orchard site. During the last two classes of the month they harvested 1.2 metric tons of squash, potatoes, corn, carrots, and apples.

It felt like a substantial harvest after spending much of the summer working on the campus terraces. The terrace harvest was spread out over six months, peaking in July, when we collected 140 kg of produce.

The orchard harvest was over in two weeks, but was more than three times as large as all six months of campus harvests combined.

The difference was due to the fact that we had 1,000 square meters to work with at the orchard, but just 288 square meters on campus. The yield per square meter was the same at both sites.

Once the harvest was in, we spread manure from a horse farm located about 350 meters from the orchard site. Our manure spreader holds about 750 liters, and we emptied it every 35 meters. We fertilized the area where we harvested potatoes.

We seeded the harvested area to a winter cover crop mix of barley and crimson clover.

Kwantlen Street Farmers Market

The start of a new semester coincided with a "sneak peek" at the Kwantlen Street Farmers Market. 

Produce grown by the Sustainable Agriculture students and the TFN Farm School students was featured near the market entrance, just behind the Richmond campus.

The market will be back in this location every Tuesday evening, beginning in the spring of 2016. It will give next year's Agroecosystems Management students a regular market outlet for the fruits of their labour. 

 

Fall harvest

Yesterday the students collected more than 100 pumpkins, more than 100 ears of corn, and more than 500 pounds of potatoes from the south Richmond orchard site.

We're rushing to get the edible food crops out so that we can apply manure and plant our winter cover crops.

Community feedback

Community feedback is a rewarding aspects of working in the campus terrace gardens. It's hard to spend much time in the gardens before a passerby stops to talk about them. It seems everyone is glad to see food growing in front of campus.

Yesterday's edition of the Richmond News featured a photograph and letter to the editor from a community member who has enjoyed watching our gardens grow this summer.

(Click image to enlarge)

The gardens have also inspired KPU Arts Advisor Naomi Ben-Yehuda, who sent us the following pictures that she took in June.

End of Summer Semester

We finished the summer semester last week.

The students harvested 288 kg (635 lbs) of produce from the campus terraces over the 17 weeks of summer classes. The harvest consisted mainly of brassicas and greens in May, potatoes in late June and early July, and cucurbits in July and August.

It was sometimes difficult to stay ahead of the summer squash. Some got too big between harvests. Cucumbers and squash accounted for almost half of the summer's yield.

Tomatoes were just coming on in earnest when the classes ended.

The sunflowers provided an impressive backdrop, but were not ready for harvest before the end of summer classes.

Bush beans kept us busy in late July, but petered out quickly due to water stress.

The carrot yield was disappointing, given the amount of space dedicated to the crop. Carrots happened to be in the area of the garden that received the second load of compost, where nothing grew well.

We have plenty of room for improvement as we build up the soil at the site in coming years.

We harvested three rows of Yukon Gold potatoes from the orchard site on August 13th. The potatoes sized up nicely and yielded well in the clay loam soil, despite having no fertilizer at all, and no irrigation until two weeks before harvest. The site's high organic matter content helped hold onto nutrients and water for the plants in a challenging year.

The corn is also looking much better at the orchard site than on the campus terraces.

Milk for powdery mildew

Powdery mildew is becoming a problem on the cucurbits and kale in the campus terrace gardens.

  

Powdery mildew on zucchini leaf

Powdery mildew on kale leaf

The disease is most severe in warm, dry weather with high relative humidity. Young, succulent leaves and plants growing in nitrogen-rich soil are most prone to infection. 

The class observed the most severe infection at the east end of the west terraces, where the squash vines are particularly large and vigorous.

Leaf wetness actually prevents infection. Our recent switch from a sprinkler irrigation system to a drip irrigation system probably made the gardens more susceptible to powdery mildew by eliminating periods of leaf wetness.

Milk can be more effective than commercial fungicides in controlling powdery mildew on cucurbits. The students pruned out infected leaves to remove sources of inoculum and increase air flow through the plants, and then sprayed the remaining leaves with a 40% solution of milk in water. They will continue to spray milk once or twice each week.

Compost trial

Introduction

Compostable organics, such as food waste, accounted for 36% of Metro Vancouver's garbage in 2013. Sending compostables to the landfill uses up limited landfill space and produces methane, which is a powerful greenhouse gas. The region has implemented an organics disposal ban in an effort to divert 70% of its waste from disposal this year. Beginning this month, tipping fees for waste haulers include a 50% surcharge for any loads that contain more than 25% food waste.

The region's green bin programs provide an alternative disposal stream for compostable organics. Food scraps and yard waste collected in household green bins are sent to several municipal composting facilities, including an operation at the Vancouver Landfill, in Delta; Harvest Power, in Richmond; and Net Zero Waste, in Abbotsford. These and other commercial composting facilities in the region help close the nutrient loop by generating natural fertilizer for the region's farms.

I visited the Harvest Power facility in Richmond in February. I was impressed by the scale of the operation, with its capacity to process 240,000 tons of organic waste into compost and biogas annually. I was grateful when the managers offered to donate compost for the student's terrace gardens at KPU's Richmond campus.

Soon after visiting the Harvest Power site, I was contacted by a representative of Net Zero Waste, who also offered to donate compost for the terrace garden project. Since we had two sources of donated municipal compost available, I asked the students to conduct a randomized and replicated experiment to compare the composts, and uncomposted control plots, in terms of crop productivity. We expected the results to be useful to our program, and to regional farmers selecting composts for soil improvement.

Methods

The two terraces east of the Richmond campus entrance were divided into 12 plots, each measuring 1 m by 3 m (Fig. 1). Plots were grouped into two blocks on each terrace, with the three plots nearest the trees in the southeast corner of campus grouped together, to control for possible terrace and shade effects.

Plots in each block were randomly assigned to one of three treatments: 1) Control (no compost); 2) Soil Amender compost from Harvest Power; or 3) Boost compost from Net Zero Waste. Neither compost was blended with sand or topsoil. Composts were applied as a 15 cm mulch layer on top of sandy soil in early April (Fig. 2).

Figure 1. Compost trial location and experimental layout.

Figure 2. Compost trial location before planting. Compost had yet to be applied
to the Net Zero plots in the upper terrace when this image was taken on April 10th.

On April 15th each plot was direct seeded with a row of lettuce (Lactuca sativa cv. 'Drunken Woman'), a row of spinach (Spinachia oleracea cv. 'Savoy'), and a row of Swiss chard (Beta vulgaris cv. 'Pink Flamingo). Rows were spaced 25 cm apart. Plots were irrigated by sprinkler as needed.

Lettuce and spinach were harvested on June 7th (Fig. 3; 53 days after seeding) and Swiss chard was harvested on July 8th (84 days after seeding). All plants were counted and weighed at harvest to calculate total yield, density, and average plant weight. Data analysis was conducted using the R statistical computing environment (Raw data and R coding in Addendum).

Figure 3. Lettuce and spinach harvest, June 7th.

Results

Compost treatment influenced total yield (Fig. 4), yield of individual crops (Figs. 4, 5), and average plant weight (Fig. 6), but not plant density (Fig. 7). Yield and average plant weight were highest in plots amended with compost from Net Zero Waste, and lowest in unamended Control plots. Swiss chard accounted for 72% of the biomass harvested from the study area (Fig. 4), so had a disproportionate influence on the total yield, but similar trends were observed across crops (Fig. 5).

Median values and distributions are compared using 'box and whiskers' charts (interpret) in Figures 4-7.

Figure 4. Total yield of lettuce, spinach, and Swiss chard in unamended
control plots (Ctrl) and plots amended with compost from
Harvest Power (HP) or Net Zero Waste (NZ).

Figure 5. Yield of lettuce, spinach, and Swiss chard in unamended
control plots (Ctrl) and plots amended with compost from
Harvest Power (HP) or Net Zero Waste (NZ).

Figure 6. Average plant weight in unamended control plots (Ctrl) and plots
amended with compost from Harvest Power (HP) or Net Zero Waste (NZ).Weight differed by compost source (left) but not replicate.

Figure 7. Plant count at harvest in unamended control plots (Ctrl)
and plots amended with compost from Harvest Power (HP) or
Net Zero Waste (NZ). Count differed by replicate (right) but not

between compost treatments.

Discussion

Compost improved yield of lettuce, spinach, and Swiss chard. The composts from Harvest Power and Net Zero increased yields by 360% and 700% of the control, respectively. Pronounced yield differences between the treatment and control plots suggest severe nutrient deficiency in the absence of compost, consistent with the low nutrient holding capacity of the high sand, low organic matter soil at the site before treatment. Germination and survival of the direct-seeded crops were similar across treatments, but weight at harvest differed between treatments, suggesting that compost treatment and compost source influenced plant growth.

Compost analysis is needed to determine why crop growth rates differed between the composts tested. Differences in nutrient content, pH, and salinity could all contribute to yield differences such as those observed in this trial.

Acknowledgements

Thanks to Harvest Power and Net Zero Waste for donation of composts used in this trial, and in the remainder of KPU's Richmond campus terrace gardens.

Addendum: Data analysis and presentation in R

A data table called 'Compost' was constructed in R.

Each row of the table contained the following 14 data points for a single plot:

1. Rep: One of four blocks, labeled A, B, C, or D
2. Treat: One of three treatments, labeled Ctrl (Control), HP (Harvest Power), or NZ (Net Zero)
3. letwt: Combined weight of all lettuce, in grams
4. spiwt: Combined weight of all spinach, in grams
5. chawt: Combined weight of all Swiss chard, in grams
6. letcnt: Number of lettuce plants harvested
7. spicnt: Number of spinach plants harvested
8. chacnt: Number of chard plants harvested 
9. letavg: Average weight of a lettuce plant, in grams (letwt/letcnt)
10. spiavg: Average weight of a spinach plant, in grams (spewt/spicnt)
11. chaavg: Average weight of a chard plant, in grams (chawt/chacnt)
12. totwt: Total weight of all plants, in grams (letwt + spiwt + chawt)
13. totcnt: Total number of plants harvested (letcnt + spicnt + chacnt)
14. Plantwt: Average plant weight, in grams (totwt/totcnt)

The null hypothesis that compost source had no effect on total yield was tested by ANOVA. The null hypothesis was rejected, and means were separated by Tukey's Honestly Significant Difference test, which found significant differences between all treatments.

> Compost.aov <- aov(totwt ~ Treat + Rep, data=Compost)

> summary(Compost.aov)

> TukeyHSD(Compost.aov) 

The null hypothesis that compost source had no effect on plant density was tested by ANOVA. The null hypothesis could not be rejected but a significant replicate effect was detected.

> Count.aov <- aov(totcnt ~ Treat + Rep, data=Compost)

> summary(Count.aov)

The null hypothesis that compost source had no effect on plant weight was tested by ANOVA. The null hypothesis was rejected, and means were separated by Tukey's Honestly Significant Difference test, which found significant differences between the two compost treatments, and between Net Zero compost and the Control.

> PlantWt.aov <- aov(PlantWt ~ Treat + Rep, data=Compost)

> summary(PlantWt.aov)

> TukeyHSD(PlantWt.aov)

Figures 4-7 were generated using the following code:

• Figure 4:

> par(mfrow=c(1,2))

> boxplot(totwt~Treat, data=Compost, main="Total yield", xlab="Compost source", ylab="Weight (g)")

> barplot(MeanWt, main="Yield by crop", xlab="Compost source", ylab="Weight (g)", ylim=c(0, 5000), legend.text=c("Lettuce", "Spinach", "Chard"), args.legend = list(x="topleft"))

• Figure 5:

> par(mfrow=c(1,3))

> boxplot(letwt~Treat, data=Compost, main="Lettuce yield", xlab="Compost source", ylab="Weight (g)")

> boxplot(spiwt~Treat, data=Compost, main="Spinach yield", xlab="Compost source", ylab="Weight (g)")

> boxplot(chawt~Treat, data=Compost, main="Chard yield", xlab="Compost source", ylab="Weight (g)")

• Figure 6:

> par(mfrow=c(1,2))

> plot(PlantWt~Treat+Rep, data=Compost, ylab="Weight (g)")

• Figure 7:

> par(mfrow=c(1,2))

> plot(totcnt~Treat+Rep, data=Compost, ylab="Plant count")