Week 4 Summer Semester (May 24 and 26) – Busy at the Orchard!

By Leanne Ejack

KPU AGRI 3390 student

After a blitz day of spreading compost, transplanting, thinning, and harvesting on the terraces on last Thursday’s class, we decided to devote both class days this week to the Orchard.

We started off Tuesday’s class by doing a check on the emergence of the crops we had planted over the last few weeks (carrots, scallions, Swiss chard, golden beets, pole beans, and potatoes), as well as the emergence of weeds. Last week the flame-weeder was taken through some of the rows, so we wanted to evaluate the effectiveness of this. There was good emergence on the potatoes and the crop is mature enough that we should be able to weed in the potato rows next class (lucky us!). There was still not much emergence on the other crop plantings, and we were having to scout around the rows trying to find any little plants that had popped through. We did see some good areas of emergence on the scallions, as well as the carrots, but less so on the beets, chard, and pole beans. 

"Baby" scallions just poking through the soil - the characteristic "crook" in the first leaves tells us it's a scallion and not a weedy grass.

We assessed the aftermath of last week’s flame weeding, but much to our chagrin it appeared that, while some of the weeds were in fact singed, they were still strong and growing. Foiled! The crop is too mature now to do any more flaming weeding, so we will have to wait until the crop is more established before we can go in and start hoeing and hand weeding.

 This little guy looks a bit crispy, but notice the fresh green growth just emerging.

Dr. Bomford also informed us that he had spotted potato tuber flea beetle (Epitrix spp.) damage on the potatoes growing in the adjacent community garden plots. While our potatoes do not show any signs of flea beetle infestation, we know they are in the area and we should be on the look-out for them for the rest of the season.

The flea beetles themselves are hard to spot, but their feeding activity produces characteristic “shot-holes” in the leaves of the potato plants. While the plant does take a very small hit to its photosynthetic capacity from this leaf-feeding, this is not the main cause of destruction by the beetles. The problem lies in the fact that the beetle often can spread harmful viruses to the plants. The beetles also lay eggs at the base of the potato plants and once the eggs hatch the larvae will feed on the tubers, creating tunnels in the tubers that make the potatoes hard to market and also open them up to pathogenic infection. 

"Shot-hole" appearance of flea beetle feeding on potato leaves.

Here in B.C., the flea beetles usually go through three generations per growing season. The first generation is often less harmful than the alter generations that occur later in the season when tubers are more mature and the beetle populations have grown. However, like most things in life, it is better to “nip it in the bud” early and control the first generation to prevent the population from getting out of hand later in the season. Unfortunately there are no organically-approved pesticides that are effective for tuber flea beetle control, so the most effective management tool is to use row covers over the potatoes as early as possible. 

After our morning inspection, we got to work planting corn and bush beans into the remaining rows of the AB block. Some students prepped the rows by raking away the clumps and smoothing away the soil while I got to use the Earthway seeder to plant the seeds. The corn seeds worked very well with the Earthway seeder and progress was fast. However, we decided to inoculate the bush bean seeds with Rhizobium immediately before planting, which made the seeds very wet as they went into the Earthway seeder. We found that the Earthway was not very good at dealing with wet seeds, and the seeds kept getting gummed up and stuck in machine instead of being nicely inserted into the soil. This meant having to go back and spent time re-planting the rows of bush beans by hand. This was frustrating, but a good learning experience to know not to put wet seeds into the Earthway®!

Corn seeds in the Earthway seeder

Ready to rock'n'roll on the Earthway seeder

Prepping the beds for corn and bush bean plantings.

Wet bean seeds after inoculation

On Thursday we got a quick crash course by Anna on proper hoeing technique and maintenance, and then got to work weeding the potatoes. After that, we went over to the east section of the orchard to look at an area of land that Anna had cultivated last week in preparation for a new planting of pumpkins this summer. 

That's a fine hoe you got there, Ms Anna!

We also got a lesson from our resident soil expert and newest faculty member, Dr. Aimee Taylor about evaluating soil texture in field using a soil texture flow chart. We found the soil to be a “silty-clay-loam”. 

Characteristic smearing pattern in clay soil that has been cultivated when wet.

 Without having to do an official soil analysis, it was obvious that this newly-plowed soil for the pumpkin patch was severely lacking in organic matter. The soil was very grey and cloddy, which indicates a high mineral content and lack of soil organic matter. Before we would be able to plant anything in it, we would need to add some organic matter to the soil by adding more compost. The issue was whether or not we should till the compost in or not. The benefit of tilling is that it would help control the weeds that were already overtaking the little field. However, tilling would negatively impact the already-compromised soil structure of the field. So it was decided that we would apply enough compost to hopefully choke out the weeds without having to cultivate the soil again.

 Site of the future "pumpkin patch" in serious need of some organic matter amendment.

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This “to cultivate or not to cultivate?” discussion got me thinking about the nature of agriculture on a more reflective level. It is important to remember that even in “sustainable” agroecosystem-based farming, we are ultimately disrupting the natural cycles of the ecosystem on a continual basis. Every year we remove biomass from the agricultural system through harvesting, and therefore must replenish the soil with biomass and nutrients from external inputs (whether these be synthetic fertilizer or organically-sourced compost).

Cultivation is one of the most disruptive activities we perform on the soil and the surrounding environment. However, because of the need to continually replenish the soil with nutrients, as well as plant new crops every year (as in the case of annual vegetable production), it is difficult to insist on 100% no-till agriculture. No-till farming is especially difficult for organic farmers that rely on cover cropping to replenish nutrients and biomass. Eventually the cover crop will have to be destroyed in order to make space for planting a cash crop, as well as to make the nutrients stored in the roots and vegetative structures of the cover crop available to whatever crop is planted next. The only effective way to avoid using herbicides to kill the cover crop is to mechanically incorporate the cover crop into the soil. This is difficult to do without some kind of disturbance to the underlying soil.

Unfortunately, as mentioned, this act of cultivating can have a very destructive impact on the soil ecosystem. Continual cultivation can create layers of compaction (“plow pan”) that disrupt soil aeration, water infiltration, and root penetration by plants. Continual cultivation can also destroy soil aggregates and increase the decomposition of soil organic matter, leading to declines in both soil structure and organic matter content. But also affected by cultivation is the little critters that make their home in the soil. These soil critters extend far beyond the earthworms, beetles, and other creepy crawlies we visibly see in the soil. In fact, the organisms you ­cannot see (the microorganisms) make up the vast majority of the soil biota. Soil microorganisms include bacteria, fungi, yeast, and actinomycetes. These microbes play a key role in the growth, development, and health of crop plants because of the essential activities these microbes perform in the soil environment. Some of these essential activities include the decomposition of organic matter, conversion of organic nutrients into mineral forms available for plant uptake, the cycling of essential elements such as nitrogen, building of soil structure, and specific mutual relationship such as plant-mycorrhizae interactions that help plants access nutrients

However, according to Dr. Taylor, we only know about 17% (or less!) of what biological organisms actually live in soil communities. “Classical” soil science used to give “three hoots” about soil organisms – soil chemistry and soil texture dominated the research and interest among soil scientists. However, in recent years more and more attention is being focused on the living nature of the soil. Last year (2015), the United Nations deemed it to be the “International Year of Soil”. The efforts of this campaign was to educate the public about the importance of soil and to expose them to the knowledge that the soil is an environment teeming with life. The main message was that all life on earth depends on healthy soil. A healthy soil with abundant, diverse microbial community is ultimately what puts food on everyone's table every single day. So before the next meal you sit down and enjoy today, I would invite you to give a little nod of gratitude and recognition to the microbial powerhouses that keep you, me, and the rest of the world, fed and happy each and every day of our lives.

For a more thorough and informative review of the importance of soil biology and how further research into soil biology may help solve critical issues such as soil degradation and climate change, please check out this paper published last year in Sustainability. 

Lehman, R.M.; Cambardella, C.A.; Stott, D.E.; Acosta-Martinez, V.; Manter, D.K.; Buyer, J.S.; Maul, J.E.; Smith, J.L.; Collins, H.P.; Halvorson, J.J.; Kremer, R.J.; Lundgren, J.G.; Ducey, T.F.; Jin, V.L.; Karlen, D.L. Understanding and Enhancing Soil Biological Health: The Solution for Reversing Soil Degradation. Sustainability 2015, 7, 988-1027.

Next week, we will be busy harvesting and preparing for the first week of the Kwantlen Street Farmers Market. This will be the first time we will actually start selling our produce and my colleague, Kathy, will tell you all about it how the first market goes.