New Podcast Episode: Soil Health for Urban Growers

EPISODE 6- Soil Health for Urban Growers

Healthy soils are essential for food production, so how can you protect soil health in your garden? Learn about the basics of soil health in this episode based on the “Community Resource Guide: Sustainable Healthy Soils in Alberta” by Sukhwinder Singh, research funded in part by AREF.

For more information on soil health check out these resources:

Community Resource Guide: Sustainable Healthy Soils in Alberta

Soil Health Workshop report

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TRANSCRIPT:

With growing food insecurity and rising grocery prices, it’s no wonder so many of us are starting to grow our own food at home. Maybe you’ve got a vegetable garden on your balcony, a garden or garden boxes in your front or backyard, a community garden plot or even a small farm.

But before you can start growing, you need to consider what you’re growing your plants in: soil.

Soil is so much more than a bag of dirt you picked up from your nearest garden center.

Soil is a naturally balanced combination of organic matter, minerals, gasses, liquids, and organisms that together support life.

It’s a living ecosystem continually undergoing various biological, chemical, and physical processes at the same time

All of these factors affect the soil which affects our plants which, then, affects our food. But soil is more than a tool for growing food. It stores, supplies and purifies water, modifies our atmosphere, manages carbon, and provides the building blocks for our ecosystem.

And no soil does all of this better than healthy soil.

If we’re going to protect the health of our soils, we have to look at soil as a dynamic, living, and finite non-renewable resource.

Regional factors such as agroclimatic conditions (soil type, crop combinations, and climate) and land use (growing trees, grains, grass) affect the soil's ability to control water flow, transport solute, retain and cycle nutrients and offer habitats for biodiversity.

Lots of human activities can affect soil health as well and can cause compaction,

erosion, salinization, loss of organic carbon, depletion or excess of nutrients, loss of biodiversity,

desertification, and contamination.

So what can we do to protect soil health? We can start by understanding the five basic land and soil management principles outlined by the US Department of Agriculture (USDA):

Principle 1: Soil Armor

Soil armor means keeping the soil covered to help control soil erosion, check weeds, mitigate soil temperature fluctuation, reduce soil compaction, and provide improved habitats to soil organisms.

The cover can be living plants, crop residues, compost, or synthetic tarps.

Principle 2: Minimum Soil Disturbance

Generally you want to try to disturb your soil as little as possible since disturbance can harm soil biodiversity and leave the soil vulnerable to erosion.

Soil disturbance can be mechanical like tillage, chemical like pesticide application, and biological like overgrazing.

You can mitigate soil disturbance through practices like conservation tillage, integrated pest management, and rotational animal grazing.

Principle 3: Plant Diversity 

Growing a variety of different plants has a lot of benefits. Monoculture farming– or growing only one type of crop at a time– can encourage blight, pests and soil depletion.

So growing multiple different types of plants can suppress diseases and pests, reduce soil depletion, increase biodiversity and provide you with a variety of different fruits and vegetables!

Principle 4: Continual Live Plants/Roots

Tying into plant diversity, having different types of plants and roots growing throughout the year improves soil biodiversity, increases microbial activity, and reduces soil erosion.

Principle 5: Livestock/Animal Integration

This one may or may not be relevant if you have a home garden– unless you have urban chickens!

Those cover crops we mentioned earlier can help feed your animals, and so can the weeds in your garden and certain crop residues – make sure you research what kinds of residues are ok to feed your animals.

With your animals helping you with weed management, you can reduce herbicide use, and your animals can provide nutrients for your soils through manure – though animal excrement requires compositing before it can be used in your garden.

So now that we understand the soil health principles, let's talk about practices that you can use in your garden.

A good way to guide your soil health practices is to consider the 6C practices of soil health:

  1. Compact reduction
  2. Conservation tillage
  3. Crop and animal diversity
  4. Continuous living plants
  5. Cover crops
  6. Compost and organic amendments

All of the 6C practices enhance the soil through different mechanisms so let's go into a little bit more detail.

Compaction reduction

Compaction is when soil particles are pressed through human activities such as regularly-used pathways or the use of heavy machinery or equipment.

Compaction reduces the size and number of pores and the volume of water and air in the soil while increasing the bulk density of soil.

Most plants find it hard to grow in compacted soil so you usually see little to no plant growth.

Lucky for us here in Canada, soil compaction is mitigated to a degree by the seasonal freezing and thawing of the ground.

It’s good to avoid unnecessary foot and vehicle traffic on your soil, especially when the soil is wet.

In the case of larger farms or plots of land, consider limiting your traffic to specific, established paths.

If you already have compacted soil, you may need to use a chisel plow or subsoiling to break up compacted layers. Make sure to wait until the soil is dry enough since working with wet soil can also cause compaction.

You can also use some cover crops for “bio drilling,” a process in which the roots of certain plants create “biodrill” channels through the compacted layers of soil. These channels are then used by subsequent crops to access the soil below the compacted layers. This method requires adequate soil moisture.

Conservation tillage

We’ve mentioned tillage a couple times already. Tillage is  ‘a mechanical act of mixing the soil to various degrees, primarily for preparing it for sowing, transplanting, or making seedbeds,’ and we just talked about how tillage can be used to deal with soil compaction. 

It has a whole host of other uses and benefits like weed control, facilitating faster decomposition of crop residues or organic amendments, incorporating amendments and soil-applied pesticides into soil, soil aeration, stimulating soil microbial activity by breaking soil organic matter that helps in maintaining soil structure, and promoting faster warming in the spring which leads to earlier or more uniform plant germination.

But, let’s think back to soil management principal 2: minimum soil disturbance.

Since tillage disturbs the soil it has all of the drawbacks that come with soil disruption like wind and water erosion, disrupting the connection between topsoil and soil microbes and can lead to compaction when the soil is wet.

So, to till or not to till?

Actually there's a third option!

Conservation tillage falls between no-till and conventional tillage and means reducing the number of passes while tilling, and reducing the depth or intensity of tillage.

While no-tillage practices are responsible for improved soils across Alberta, which tillage practices are most effective depends on several factors:

Climate

No till can be better for drier regions since it helps conserve soil moisture whereas tillage helps dry up wet soils for planting.

Pest and Weed control

In conventional farming, pests and weeds are managed through the use of pesticides and herbicides while on organic farms, tillage is used to manage weeds and pests.

Soil Type

Poorly drained clay-textured soils may make it more difficult to transition to no-till.

Acidity

Pay attention to your soil’s ph if you choose no till as acidity can build up on soil surfaces due to ammonium based fertilizers. If you’ve already been using conventional farming practices, you may already have a build up of acidic soil which may make transitioning to conservation or no tillage difficult, especially if you’re also transitioning to organic farming practices.

Residues

Often crop residues are incorporated into the soil through tillage to provide organic amendments to the soil. However leaving the residues as soil cover not only mitigates the negative effects of tillage but also gives you the added benefits that come with soil armor. Be aware that certain crops leave more or less residues and you may need to use new equipment or techniques to adapt to crop residues.

Continuous Living Plants

Living plants and the aforementioned crop residues provide that soil armor we were talking about in the soil health principles section.

In addition to the benefits we discussed before. Living plants also minimize soil disturbance, cycle nutrients and water, supply organic inputs through roots and litterfall, conserve moisture and prevent erosion.

Continuously living plants is the only 6C soil management strategy that protects the soil, improves diversity AND builds carbon!

These plants can be perennials, pastures and forages.

Options are limited for plants that will grow over the winter but winter wheat and fall rye will survive through the winter.

Other strategies like growing cover crops in the fall and early spring, intercropping which is growing two or more crops in proximity, agroforestry which is integrating trees and shrubs, and planting woody plants can also improve diversity, provide habitats for pollinators and other fauna, store soil carbon, manage pest attacks, and regulate water and nutrient cycles.

Cover Crops

Cover crops also provide soil cover– or soil armor– and are a category of crops that provide different types of ecosystem services.

There are 5 categories of cover crops:

Legumes

Legumes actually fix nitrogen in the soil due to bacteria that live in their roots. They also suppress weeds, reduce erosion, and improve soil structure.

Some legume cover crops are: field peas, lentils, chickpeas, vetch and clover.

Warm-season (C4) grasses

Warm season grasses increase biomass and carbon in the soil by extending plant duration.

In Alberta, these include sorghum and millet.

Warm-season broadleaves

Warm season broadleaves add biodiversity; and flowering broadleaves will supply pollen for pollinators.

Sunflowers and buckwheat are in this category.

Cool-season (C3) grasses 

Cool-season grasses grow quickly and can survive over winter, providing cover even in the coldest months.

Cereal rye is a good option from this category.

Cool-season broadleaves

These broadleaves grow quickly and have deep roots which can have the added benefit of reducing soil compaction. The deep roots can also help move macro and micro nutrients from deeper in the soil to higher up which will aid subsequent crops.

Some cover crops in this category are turnips and radishes.

Along with the benefits we already discussed, as cover crops decompose, they enhance microbial activity which increases soil organic matter and improves water holding capacity and nutrient cycling. By covering the soil, cover crops reduce water and wind erosion that would otherwise reduce soil aggregation and promote carbon loss.

Cover crops are a great way to increase your soils’ rainfall capacity.

Crop and animal diversity

We already talked about how avoiding monoculture farming can help with pests and diseases, but crop diversity has lots of other advantages! Diversity increases stability which makes your plants more resilient to abiotic stressors – like temperature fluctuations, salinity and drought or flood – and biotic stressors – pathogen infection from things like bacteria, fungi and insects.

To increase crop diversity, you’ll want to use a combination of intercrops, cover crops and perennials. Consider which crops can be grown at which times of year and which crops and plants can be grown together.

Choosing to raise animals will also improve your farm diversity and increase carbon in the soil through manure.

Be aware that having a wider variety of crops can be a bit more costly and require more maintenance. You may want to look into whether what you’re planting will require special equipment for harvesting.

Compost and organic amendments

Any time you add a carbon-based material to the soil, that is organic soil amendment. This includes “waste” from humans, animals, food and plants: so your compost, residues and animal feces. Organic amendments have lots of soil health benefits. They increase water availability and capacity, microbial activity and nutrient availability and help improve soil carbon. It’s usually best to add amendments in the spring or fall after harvesting crops. Depending on the type, your amendments can be added directly or may need to be processed.

You may already be composting your food waste. Composting is a form of processing amendments. Traditionally, composting can be done in your backyard and involves decomposing organic matter – your food scraps, yard waste and, potentially even sewage – into an organic component called humus that is then added to your soil as an amendment.

Look into what composting programs and resources are available in your municipality.

Amendments can be super beneficial to your garden but require a bit more technical knowledge. If you’re interested in amendments, there are a few challenges you need to consider.

Human and animal waste-based amendments contain pathogens and are regulated by the provincial government. Make sure to follow the provincial guidelines to prevent negatively affecting air, soil, ground and surface water.

Tillage may be required to add amendments which is a problem if you’re wanting to take a no-till approach.

Amendments can cause concentrations of phosphorus, potassium, zinc and salt which can negatively affect human, animal and environmental health.

So as you go about your food growing journey, remember that we can’t talk about growing food without talking about soil health. Soil is a natural resource, an amazing one, that can provide for and take care of us as long as we provide for and take care of the soil.

Keep in mind the soil health principles:

  1. Soil Armor
  2. Minimum Soil Disturbance
  3. Plant Diversity
  4. Continual Live Plants/Roots
  5. Livestock/Animal Integration

And consider which soil health practices might best meet your garden’s needs. 

Happy growing!

For more information check out the Community Resource Guide: Sustainable Healthy Soils in Alberta on the Alberta Land Institute’s website and check out the resources listed in the description.

Based on the Community Resource Guide: Sustainable Healthy Soils in Alberta by Sukhwinder Singh. Research funded in part by the Alberta Real Estate Foundation (AREF)