Crop Rotation - A Simple Yet Highly Effective Strategy

Crop rotation is an important part of organic gardening. After you spend a lot of time building up healthy soil you don't want it to be overrun with pests or soil diseases.

By moving your crop families around to different areas of the garden you keep both the soil and the plants healthy.

What Is Monoculture and Why Is It Bad?

Monoculture which is popular in commercial agriculture tends to deplete soils and allow pest and disease organisms to increase in population.

Monoculture refers to the practice of growing a single crop in a large area of land, year after year. This agricultural model has gained popularity over the years because for farms it is more efficient. However, monoculture poses several ecological and agricultural challenges.

When a single crop is repeatedly cultivated in the same area, it creates an ideal environment for pests and diseases to thrive. As a result, many commercial farmers often resort to using large quantities of chemical pesticides and fertilizers.

This kills many beneficial insects as well leading to a loss of biodiversity affecting pollinators and wildlife such as birds and toads which eat insects.

Monoculture undermines soil health and fertility because it depletes essential nutrients from the soil. Certain plant species need certain nutrients for example broccoli is a heavy nitrogen feeder and tomatoes need calcium. When you plant the same crops you deplete the nutrients the plant needs most.

Crop Families

Scientists divide crops into families based on similarities. The important thing to know is that crop families are affected by similar pests and like the soil to have certain nutrients.

1. Brassicaceae - Cruciferous Family

• Scientific name: Brassicaceae

• Common names: Cabbage family, Cruciferous vegetables

• Example crops: Cabbage, Kale, Broccoli, Brussels Sprouts

2. Solanaceae - Nightshade Family

• Scientific name: Solanaceae

• Common names: Nightshade family, Solanaceous vegetables

• Example crops: Tomato, Potato, Pepper, Eggplant

3. Fabaceae - Legume Family

• Scientific name: Fabaceae

• Common names: Legume family, Bean family

• Example crops: Beans, Peas, Lentils

4. Cucurbitaceae - Gourd Family

• Scientific name: Cucurbitaceae

• Common names: Gourd family, Cucurbit vegetables

• Example crops: Squash, Cucumber, Melon, Pumpkin

5. Asteraceae - Aster Family

• Scientific name: Asteraceae

• Common names: Aster family, Composite vegetables

• Example crops: Lettuce, Artichoke, Sunflower

6. Apiaceae - Carrot Family

• Scientific name: Apiaceae

• Common names: Carrot family, Umbelliferous vegetables

• Example crops: Carrot, Celery, Parsley, Dill

7. Alliaceae - Onion Family

• Scientific name: Alliaceae

• Common names: Onion family, Allium vegetables

• Example crops: Onion, Garlic, Shallot, Leek

8. Chenopodiaceae - Goosefoot Family

• Scientific name: Chenopodiaceae

• Common names: Goosefoot family, Chenopod vegetables

• Example crops: Spinach, Swiss Chard, Beetroot

9. Poaceae - Grass Family

• Scientific name: Poaceae

• Common names: Grass family, Cereal crops

• Example crops: Corn, Wheat, Rice, Barley

10. Asterideae - Asterid Family

• Scientific name: Asterideae

• Common names: Asterid family, Root vegetables

• Example crops: Carrot, Turnip, Radish, Beet

Please note that this list includes only a few examples from each family, and there are many more vegetables within each family.

Why Are Crop Families Important?

1. Disease and Pest Management:
One primary reason crop families are important to understand is their relationship to diseases and pests. Many pests and diseases tend to attack specific crop families or have a preference for particular plants.

By rotating crops within or across families, gardeners can disrupt the life cycles of pests and make it harder for diseases to take hold and spread. Some insects can travel but many have a small territory especially in the larvae form.

So for example, tomatoes. The most popular vegetable grown. Tomatoes as well as other crops in their family such as peppers like and need calcium. They are also prone to many soil-borne diseases such as wilts, blight, and septoria.

So what does that tell us? Well, we want to plant our tomatoes somewhere where we haven't planted them for the last several years AND we want to prepare the soil with nutrients that help them thrive. So make sure the soil is rich in nutrients including calcium.

2. Nutrient Management:
Different crops have distinct nutrient requirements. Some crops may deplete specific nutrients from the soil, while others may enrich it. Understanding crop families helps farmers effectively manage soil nutrients through crop rotation.
Legume crops, like beans and peas, have a symbiotic relationship with nitrogen-fixing bacteria in their roots. These bacteria convert atmospheric nitrogen into a form that plants can use, enriching the soil with nitrogen.

3. Soil Health and Structure:
Crop families also offer insights into plant root systems and their impact on soil health and structure. Some plants have deep taproots that help break up compacted soil layers and improve drainage, while others have fibrous root systems that help prevent erosion and retain moisture.
By rotating crops with different root structures, gardeners can ensure soil is not constantly subjected to the same pressures, reducing soil erosion and compaction. This practice improves soil health, and structure, and promotes the availability of nutrients, water, and oxygen to plants.

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4. Weed Management:
Understanding crop families can assist farmers in managing weeds. Some weeds are specific to certain crop families or have preferred hosts. By practicing crop rotation, farmers can break the weed life cycle and reduce weed pressure.
For instance, the Brassica family (Cruciferae) includes crops such as cabbage, kale, and broccoli. Certain weeds, like common mustard or wild radish, are also part of this family. By rotating crops within this family, farmers can disrupt the weed lifecycle by alternating crops with different weed susceptibility.

How Do I Plan For Crop Rotation?

Planning is important. This is why I have a crop rotation log in my (#ad) garden planner. Whatever kind of system you use whether online or paper you want to give each garden section a number or name. That way you can track what you plant where over the years. Certain crops also do well following other crops.

Crop rotation is fairly easy in larger gardens. You can organize your rows or beds to hold one family of crops.

Square foot gardening is nice because it naturally has you putting the same plants in each square. That way you always follow with a different plant family.

I grow a lot of things in grow bags which is great because I just keep labeling the bag with what it has in it and then next year I will use it for a different plant.

A popular three-year rotation is beans, corn, and squash. Each one of these crops helps the next crop. Beans fix nitrogen, corn roots break up the soil, and squashes protect the soil.

Another good three-year rotation that has proven benefits is lettuce followed by onions followed by cabbage or any other brassica.

Crop rotation also helps control weeds. Some crops encourage weeds just by the way they grow. Corn allows the sun to reach the soil during the growing season so requires lots of vigilance to keep weeds out of the patch.

Squash plants have large leaves which shade the soil and help to inhibit weeds.

Using Cover Crops in Your Crop Rotation Plan

Part of your crop rotation may focus on soil building. So you may plan on a section or bed of your garden devoted to planting a cover or green manure crop. I often grow a cover crop that contains a mix of Sudan grass, radish, and clover.

This will grow for a season before I till it into the soil to decompose and add nutrients.

Cover crops, often referred to as "green manure," play a vital role in reducing erosion, increasing organic matter content, suppressing pests and diseases, and enhancing nutrient availability.

Cover crops help in numerous ways:

1. Erosion Control:
Cover crops act as a natural barrier against wind and rain erosion. By planting leguminous cover crops like clover or hairy vetch, nitrogen-fixing properties help stabilize the soil structure. Their dense foliage protects the soil surface from heavy rainfall, reducing the risk of nutrient runoff and topsoil loss.

2. Boosting Organic Matter:
Integrating cover crops into a crop rotation regimen dramatically increases organic matter content in the soil. As the cover crops grow, they photosynthesize, capturing carbon dioxide from the atmosphere and sequestering it in the form of root biomass. Upon decomposition, this organic matter enriches the soil, enhancing its water-holding capacity, increasing nutrient availability, and promoting the growth of beneficial soil microorganisms.

3. Suppressing Pests and Diseases:
Certain cover crops, such as mustard or oilseed radish, possess natural biofumigant properties. These crops release compounds that help suppress soil-borne pests and diseases, and they provide habitat and food sources for beneficial insects, aiding in natural pest control.

5. Weed Suppression:
Competitive cover crops effectively crowd out weeds, limiting their growth and propagation. The dense canopy created by cover crops shades out emerging weed seeds, preventing them from receiving adequate sunlight for photosynthesis.

In a large garden its fairly easy to plant families together and then rotate the rows or beds every year.

Letting a Bed Rest During Rotation

Part of rotation can be just letting a garden bed rest as well. Add some compost and leave that section unplanted for a season. Make the time to continue weed management so you continue to control and discourage perennial weeds from establishing.

Letting a section of the garden rest or lay fallow helps restore the soil’s natural nutrient balance. Giving the soil a chance to rest can also reduce pests and soil-borne diseases since they don’t have anything to eat.

Crop Rotation In Containers

Growing in containers offers a unique situation. In this case, you may end up just dumping the soil into your compost bin and then adding fresh soil the next time you plant that container.

Remember it is important to occasionally sterilize your containers to prevent disease spores from living in them. Organisms can attach themselves to the fabric in grow bags and the sides of porous clay pots.

If you store your containers with soil in them remember to place a label in the soil reminding you what crop it held. That way you make sure not to repeat the same plants.

Crop Rotations and Succession Planting

All of this talk about annual rotations may have you wondering but what about succession planting? I'm glad you asked! You may grow several successions of crops like lettuce and spinach every year.

Succession planting may be a necessity if you have a small urban garden. And it gives you greater production. You may have two or three crop families in a bed each season. That's perfectly ok. Just keep it in your brain or written in your planner what you planted where during the growing season.

You may even have the same crop growing repetitively in one bed over the growing season. For example, you start with red sails lettuce in spring because they like cool weather and grow fast. You switch to Jericho lettuce in summer which is more heat tolerant and then to Arctic King lettuce in fall. The next year you succession plant onions and garlic in that bed.

Succession planting and crop rotation can easily fit into an urban garden.

Author, Ame Vanorio, is a Master Gardener, has 30 years of organic gardening experience, and loves the smell of fresh-tilled earth. Check out her books available on Amazon. Some are also available on PDF in our Store.