Crop Rotation

How Diversity Drives Biological Success on Farms

Fostering Natural Systems on the Farm
In nature, monoculture doesn’t exist. Diversity is inherent in every thriving ecosystem. Regenerative organic agriculture seeks to reflect this natural balance by mimicking natural systems and working with nature, not against it. As the saying goes, “work smarter, not harder.”

When producers build diversity into their land management strategies, life begins to spark and unfold. To grow healthy, nutritious food, you need soil life to support plant life, and plant life to support human life. Humans are stewards of these relationships.

Increasing Biodiversity on the Farm
Producers can build diversity into their fields through a variety of practices, such as:

• Crop rotation
• Cover crops
• Intercropping

It’s important to remember that there is no one-size-fits-all approach to how the principle of diversity is added into a farm system. Producers choose what works best for their specific context and local conditions.

Diversity: A Summary
Without diversity, agricultural systems become vulnerable and fragile; pest and disease pressures increase, and key ecological processes like the water cycle, nutrient cycle, energy flow, and community dynamics begin to break down. A lack of variety above and below ground limits microbial life, making it harder for plants and soil organisms to form the symbiotic relationships that support ecosystem functions.

Introducing diversity strengthens the soil food web and supports the entire system, which builds a resilient, biologically-active soil microbiome that sustains life both below and above ground.

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Diversifying crops through spatial and temporal strategies enhances agroecological practices and ecosystem services.

Temporal diversity involves crop rotation and cover cropping, adjusting timing annually, while spatial diversity includes selecting crops for specific field conditions and using strip cropping.

By integrating these strategies, farmers can create resilient, productive agroecosystems.

It Makes Economic Sense

Sustainable farming requires long-term profitability alongside responsible resource management.

While external inputs can threaten financial and environmental sustainability, crop rotation is essential in both organic and regenerative practices. It reduces the need for inputs, boosts nutrient cycling, improves soil health, and manages weeds and diseases.

When planning rotations, farmers should consider immediate challenges, long-term soil health, and profitability with high-performing crops and strong markets.

It Fits Agronomically

Select crops for rotation based on your farm’s unique conditions, such as soil type, climate, and pest pressures. The right crop choices and rotation sequence optimize nutrient use, improve soil structure, and support beneficial microbes. This approach helps manage pests, build soil health, and enhance farm resilience, while also meeting cash flow needs.

Taking a place-based approach, considering the specific conditions of each field, is crucial. By understanding local factors, farmers can choose the most suitable crops for their rotation, improving productivity and promoting ecological balance and long-term resilience.

It Contributes to Soil Health

Crop rotations are a fundamental tool in agriculture, involving the sequence of at least two, and sometimes up to seven, different crops over multiple growing seasons. Each crop has unique growth needs and benefits the soil in different ways, creating balance in the rotation.

By selecting crops that enhance ecological processes such as water cycling, nutrient cycling, energy flow, and community dynamics, crop choice contributes to improved soil health.

It Balances Nutrient Needs with Availability

Crop rotation helps maintain nutrient balance by leveraging the unique interactions between plants and soil. Different crops have varying nutrient needs—such as nitrogen, phosphorus, and potassium—so rotating them prevents nutrient depletion and supports a healthy soil biome. Legumes like peas and alfalfa enrich the soil by fixing nitrogen, while deep-rooted crops access nutrients from deeper layers.

Including a high-biomass legume before nitrogen-demanding crops is crucial, as it ensures nitrogen is available for crops, rather than being taken up by weeds.

Nutrient Budgeting App

To assist in managing these nutrient needs, the Nutrient Budgeting App helps you assess whether nutrients are accumulating or being depleted from your fields over time. It streamlines the process of calculating the nutrients you’re applying, ensuring a balanced approach to nutrient management.

Follow this link to create an account to access the Nutrient Budgeting App: https://www.thenutrientbudget.com/

It Adds Diversity

Crop rotation boosts both above- and below-ground diversity. Diverse crops help prevent pest and disease outbreaks and support a varied soil food web, enhancing soil function and microbial diversity.

Plant diversity also aids in resisting disturbances and restoring degraded ecosystems. Techniques like under-seeding, intercropping, and strip planting help farmers promote healthier soil ecosystems.

It Keeps Weeds Guessing

Crop rotation helps control weeds by creating varied environments that disrupt weed growth patterns. Different crops alter conditions seasonally, making them unfavorable for certain weeds.

Two strategies for weed management through rotation include:

• Selecting crops that outcompete weeds, like tall hemp shading shorter weeds
• Altering soil conditions, such as fall-seeding to displace weeds before spring cultivation.

It Balances Workload and Machinery Availability

Crop rotation, such as winter wheat, fall rye, dormant-seeded canola, silage and hay, can be strategically designed across the farm to improve time management by enabling farmers to spread their workload over a longer period. This approach allows for more efficient use of equipment and labor, as various crops are planted, cared for, and harvested at different times throughout the growing season.

By collaborating with nature, farmers can work smarter, not harder.

Alletto, L., Celette, F., Drexler, D., Plaza-Bonilla, D., & Reckling, M. (2022). Editorial: crop diversification, a key pillar for the agroecological transition. Frontiers in Agronomy, 4. https://doi.org/10.3389/fagro.2022.950822

Bergez, J. E., Audouin, E., & Therond, O. (2019). Agroecological Transitions: From Theory to Practice in Local Participatory Design. Springer. https://biovallee.net/wp-content/uploads/2019/07/2019_Book_AgroecologicalTransitionsFromT.pdf

Magdoff, F., & VAN ES, H. (2021). Building Soils for Better Crops: Ecological Management for Healthy Soils. Sustainable Agriculture Research and Education (SARE). https://www.sare.org/wp-content/uploads/Building-Soils-for-Better-Crops.pdf

Gebremedhin, B., & Schwab, G. (1998). THE ECONOMIC IMPORTANCE OF CROP ROTATION SYSTEMS: EVIDENCE FROM THE LITERATURE. Research in Agricultural & Applied Economics. https://doi.org/10.22004/ag.econ.11690

Merfield, N. C. (2019). Rotations and their Impact on Soil Health. The BHU Future Farming Centre. https://www.low-impact-farming.info/sites/default/files/2020-05/rotations-and-their-impact-on-soil-health-2019-ffc-merfield.pdf

Sela, G. (2024, October 31). Crop Rotation – A Sustainable Approach. Cropaia. https://cropaia.com/blog/crop-rotation/

Verdesian Life Sciences. (2024, September 16). Crop rotation benefits. https://vlsci.com/blog/crop-rotation-benefits/

Pedrinho, A., Mendes, L. W., de Araujo Pereira, A. P., Araujo, A. S. F., Vaishnav, A., Karpouzas, D. G., & Singh, B. K. (2024). Soil microbial diversity plays an important role in resisting and restoring degraded ecosystems. Plant and Soil, 500(1–2), 325–349. https://doi.org/10.1007/s11104-024-06489-x

Saskatchewan Agriculture. (2018, February 22). Sustainable agriculture: The benefits of crop rotation [Video]. YouTube. https://www.youtube.com/watch?v=XzSchrmBt8g

Yang, X., Hu, H.-W., Yang, G.-W., Cui, Z.-L., & Chen, Y.-L. (2023). Crop rotational diversity enhances soil microbiome network complexity and multifunctionality. Geoderma, 436, 116562-. https://doi.org/10.1016/j.geoderma.2023.116562

eOrganic. (n.d.). Keep the Weeds Guessing with Crop Rotations. https://eorganic.org/node/2496

Verdesian Life Sciences (2024). Crop Rotation Benefits. https://www.cropscience.bayer.us/articles/bayer/benefits-management-crop-rotation

Zylstra, J. (2008). Crop Rotations in Direct Seeding. Alberta Agriculture and Rural Development. https://www.cropscience.bayer.us/articles/bayer/benefits-management-crop-rotation

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A Rundown on Inter-Plant Competition 

What Is Allelopathy?

Allelopathy is a biological phenomenon where plants produce secondary metabolites called allelochemicals that impact the ability of other organisms to grow. Allelochemicals can reside in plant tissue where they can prevent insect and/or herbivore predation, or they can be secreted from the roots where they can affect the growth of bacteria, fungi or other plants. These root secretions not only have the ability to prevent other plants from growing but can sometimes even prevent seeds from germinating.

Why does it matter?

Although allelopathy can be a strong positive mechanism used to manage inter-plant competition and suppress weeds, it can also create in-field challenges – especially if a desired crop is being inhibited by the allelopathy of a different crop. Knowing the effects that plants may have on each other is important in crop management. 

Allelopathy as a Management Tool

Cover Crops: Rye as a cover crop is a well-known weed suppressor. It contains an active allelopathic compound called “diboa”. Brassicas also inhibit weed germination and growth.

Green Manure: Rye mulch that is roller crimped or left on the soil surface will starve weeds of nitrogen while seeded crops are strong enough to push through the cover. Buckwheat grows quickly and creates a dense canopy that suppresses weed growth. When it’s incorporated back into the soil, it also has allelopathic chemicals that further inhibit weed germination and growth while improving soil structure.

Allelopathy as an In-field Challenge

Intercropping: When growing multiple species together in an intercrop of cover crop system, it is important to understand which plants might inhibit one another through allelopathy and avoid growing antagonistic combinations. Sunflowers release allelochemicals such as sesquiterpene lactones, which can inhibit the growth of nearby plants. This can be especially harmful if sunflower is not the cash crop.

Crop Rotation: Alfalfa is well known to have an allelopathic effect on subsequent plantings of the same species. Avoid seeding alfalfa into terminated alfalfa to prevent this issue. Also, ensure seeding rate is adequate the first time as you may not have the option to return later. Mustard crops release glucosinolates, which break down into bioactive compounds that can suppress weed growth and soil-borne pests. However, these compounds can also negatively affect the growth of subsequent crops.

Managing Allelopathy 

While this is a simplification, there are a great deal of management decisions that greatly impact crop production when allelopathy is taken into account. What observations have you made with crop rotations and cover crop mixes? Are there crops that don’t do well following another crop? Are there crop mixes you have done that had particular plants that did not do well? This may be due to allelopathy. Through observations and further research, you too can harness the power of allelopathy!

Links for further information

• Lessons from Allelopathy (Video)
• Allelopathy and Cover Crops (Information Sheet)
• Using allelopathic and cover crops to suppress weeds (Article)
• Allelopathy – Everything You Need To Know About It (Video)
• Effect of Allelopathy on Plant Performance: A Meta-Analysis (Journal Article)
• Allelopathy: Advances, Challenges and Opportunities (Chapter)
• Does Cultivar Matter, from Allelopathy to Decomposition (Video)

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Crop Rotation as a Tool for Diversification

Introducing diversity into field crop operations strengthens soil food webs and supports the agroecosystem as a whole. It builds a resilient, biologically-active soil microbiome that sustains life both below and above ground. Crop rotation, cover cropping and intercropping are practical tools for building diversity into cropping systems both across space and time.

What Is Crop Rotation?

Crop rotation is the practice of planting different crops or crop families (such as cereals, oilseeds, legumes, broadleaf plants, and root crops) in a field from year to year, introducing time-based diversity through plant variation. This includes crops with different nutrient needs and outputs that support soil chemistry and biology, along with root structures that influence the physical condition of the soil.

Crop Rotation in Organic Farming

In organic farming, crop rotation is a foundational tool used to disrupt pest and disease cycles without relying on synthetic inputs, while also improving both soil and financial capital. When planned intentionally, crop rotation supports long-term productivity – not by depleting natural resources, but by contributing to their regeneration.

How Are Rotations Planned?

Crop rotations are carefully planned to account for how each crop affects the soil and which crops grow best in sequence, as different crop families have varying nutrient needs and will either deplete or contribute nutrients to the soil. Other important factors include marketability, pest and disease control, weed management, and building soil organic matter.

Crop Rotations on the Canadian Prairies

On the Canadian Prairies, a typical crop rotation involves three main crop types:

Cereals: Wheat, Barley, Oats, Corn, Rye

Oilseeds: Canola, Flax, Mustard, Sunflower

Legumes: Lentils, Peas, Chickpeas, Clover

Rotations typically follow a 3-, 4-, or 5-year cycle, with a common pattern being cereals followed by oilseeds, then legumes. This sequence helps balance nutrient demands and supports long-term yields and productivity.

Categories of Crops based on Nutrient Demand

Heavy Feeders: Crops that draw large amounts of nutrients from the soil, especially nitrogen. These include corn, canola, sunflowers, winter wheat, and spelt.

Medium Feeders: Crops that place a moderate demand on soil nutrients. Examples include spring wheat, oats, rye, and winter barley.

Light Feeders: Crops that require fewer nutrients and are easier on the soil. These include spring barley, flax, buckwheat, and soybeans.

Givers: Crops that give back to the soil by adding nutrients. Examples include nitrogen-fixing plants like peas, beans, alfalfa, clover, and vetch.

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The Means and the Methods

What is Intercropping?

Planting different species and varieties from multiple plant families during the same growing season is a strategy producers can use to increase diversity in their land management practices. This approach is known as intercropping — the practice of growing two or more crops close together, whether in the same row, in alternating rows, or in nearby strips. These crops are managed to support one another, helping to make better use of natural resources (i.e., light, water, and nutrients) while also improving yields, reducing pests and diseases, and attracting beneficial insects.

Intercropping Can Involve:

– Growing two or more cash crops at the same time.

– Planting a cash crop alongside a cover crop.

– Growing a mix of cover crops together.

Intercropping Requires Planning

Intercropping is a useful strategy for adding diversity to a cropping system, but it requires careful planning. Timing needs to be managed so one crop doesn’t outcompete the other, and mixing plant families can make crop rotation more complex, potentially increasing pest and disease pressure. In dry climates, water use is also a key consideration, as intercropping and cover cropping can increase demand for limited moisture, making water conservation important.

Intercropping Methods: Temporal

Adding diversity through time staggering planting or harvest times.

Intercrop Method	Definition
Relay cropping	Planting a second cash crop or forage into a field that already has a cash crop growing. Both crops grow together for a short time. The first crop is harvested, and the second continues growing until it is ready to harvest.
Interseeding	Planting a cover crop between or into the rows of a growing cash crop, usually early in the season. The cover crop grows slowly while the main crop is established, then takes off after harvest.
Underseeding	Planting a cover or forage crop early in the season beneath a cash crop. The underseeded crop establishes roots, slows down while shaded, and begins growing again after the cash crop is harvested.
Overseeding	Planting cover or forage seeds over existing crops, crop residue, or pasture without disturbing the soil — often done after harvest or in thinning stands to improve ground cover or extend forage.

Intercropping Methods: Spatial

Adding diversity across space — growing multiple crops in the same area.

Intercrop Method	Definition
Intercropping	Planting two or more crops in the same field at the same time, without a specific row or pattern.
Row Intercropping	Planting at least one of the companion crops (either a cash crop or a cover crop) in a single or double row alongside another crop.
Strip Cropping	Planting crops (typically cash crops) in distinct areas that are spaced out enough to minimize competition and allow for separate management, yet close enough to benefit from each other.
Alley Cropping	Planting rows of trees or shrubs (such as hardwood, nut, or fruit trees) to form alleys on cropland, where cash crops or cover crops are grown in between.

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What Are Cover Crops?

Cover crops are part of a crop rotation system and are typically planted between cash crops to improve soil health (i.e., by keeping the soil covered during times when it would otherwise be left bare). Cover crops are often terminated and incorporated back into the soil, but sometimes they are also grazed by livestock. They act like the support crew on the farm – replacing nutrients used by the previous crop or adding what’s needed for the next. In terms of nutrient demand, cover crops are often considered givers, especially when nitrogen-fixing plants are included.

Why Incorporate Cover Crops?

Beyond nutrient cycling, cover crops provide ground cover and living roots that help hold soil in place, prevent erosion, add organic matter (biomass), improve soil structure, support water movement, reduce runoff, and limit compaction (since bare soil is more likely to get packed down). In this way, cover crops set the stage for the next crop in the rotation.

Thinking Ahead

Land management in a regenerative organic system takes the long view. Producers think in multi-year phases, knowing that crop diversity isn’t just about what’s grown this season, but how each crop connects to what came before—and what comes after.

When To Plant Cover Crops

Depending on their goals, producers can plant cover crops during the transition between cash crops or even dedicate an entire season to them.

(1) Shoulder season cover crops are planted after one cash crop is harvested and before the next is seeded in spring. They might be seeded alongside a growing crop or shortly after harvest, helping to keep soil covered through fall and into winter.

(2)  Full season cover crops are grown in place of a cash crop for the entire season. A producer might choose this route instead of leaving the field fallow to regenerate the land, build nutrients, or improve problem soil conditions.

Common Cover Crops

Common crops that Prairie-based Canadian producers use include oats, clover, peas, radish, hairy vetch, fall rye, phacelia, sweet clover, sunflowers, and sorghum. 

Cover Crops Add Diversity

Cover crops give producers two ways to add diversity: by planting a single species and rotating it over time (temporal diversification), or by planting multi-species mixes (spatial or plant-based diversification). Choosing a multi-species cover crop is based on the principles of intercropping — selecting species that complement and support each other to deliver multiple ecosystem benefits. 

Examples of multi-species cover crops used on the Prairies:
– Oats, peas, radish
– Ryegrasses, phacelia
– Alfalfa, flax
– Spring wheat, barley, chicory, sweet clover
– Winter wheat, faba bean, hairy vetch, plantain
– Lentils, corn, triticale

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What Are Functional Groups?

Functional groups of plants are clusters of species that share similar management needs, contribute to the environment in comparable ways, and provide similar ecological functions. There are many functional groups of plants that possess unique characteristics. For example, corn is a grass (graminoid), and soybean is a legume. These two plants are from two different functional groups, and their biology is very different. They differ in the size and shape of their leaves, their methods of seed and flower development, the size and composition of their stems, and their root systems.

What Are Some Examples of Functional Groups?

There are many functional groups, but in regenerative organic agriculture, a few key groups can really get you started:

• Forbs are flowering plants that are herbaceous (not woody), and they have broad leaves.
• Graminoids are herbaceous, flowering grasses that have long, blade-like leaves and fibrous roots.
• Legumes are flowering plants that are part of the Fabaceae family, and they have broad, round, compound leaves.
• Brassicas are a group of flowering plants that are also known as cruciferous plants. They often have lobed or entire leaves arranged alternately.

How Are Some Important Crops Categorized?

Here are some notable species and their respective functional groups:

• Forbs: Phacelia, Plantain, Sunflowers, Flax, Chicory, Burnet
• Grasses: Oat, Rye, Wheat, Cereal, Corn, Timothy
• Legumes: Red Clover, White Clover, Alfalfa, Soybean, Vetch, Lentils
• Brassicas: Cabbage, Mustard, Radish, Turnip, Kale, Broccoli

What Are the Benefits?

By adding species from different functional groups into your crop mix, you are:

• Fortifying the soil with an array of minerals
• Broadening the diversity of the soil microbiome
• Setting up defences against disturbances that target certain crops

What do each of these functional groups contribute to your farms?

• Grasses have expansive root systems that hold soil and create vast underground networks.
• Legumes are host to nitrogen-producing bacteria and can vastly improve your in-soil nitrogen.
• Brassicas have large tap roots that can really drill away at compaction. When they rot, they also contribute a lot of organic matter to the soil.
• Forbs foster diversity both above ground and below. Each species provides soil microbes with different exudates, increasing resilience to adverse conditions.

What’s the Take Home Message?

Including a diverse array of functional groups in your crop mix can enhance biological activity in the soil, boost microbiome biodiversity, and expand the positive contributions of individual plants to the environment. This, in turn, stabilizes the crop field and improves crop yield.

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