Crop rotation matters in the vegetable garden 

Raising a vegetable garden with years of continuous success and high-yielding plants is a skill. However, it’s not just a matter of having a green thumb. Utilizing crop rotation in the garden can provide similar benefits for horticulturists as it does for farmers who apply these practices in their fields.

David Hillock, consumer horticulture Extension specialist at Oklahoma State University, said planting the same annual vegetables in a specific garden location year after year is a common mistake among gardeners.

“It’s especially a problem if a gardener only likes growing a particular vegetable, like tomatoes, or if they have limited space,” Hillock said.

All in the family

Cynthia Domenghini, horticulture Extension specialist at Kansas State University, agreed with Hillock. She said gardeners can also run into problems with their vegetable crop if they grow the plants in the same families in one area year after year.

“Crop rotation requires planting any member of one plant family in a location where that plant family was not grown in the previous season,” Domenghini said. “You could plant a veggie from a different family in that spot, you could grow a cover crop or you could cover the soil with mulch and leave it unplanted.”

Most annual plants commonly grown in vegetable gardens fall within nine plant families.

Amaryllidaceae, also known as the onion or lily family, includes onions, garlic, leeks, and chives. Brassicaceae, also known as the cabbage or mustard family, includes broccoli, brussel sprouts, cabbage, cauliflower, kale, radishes, and turnips.

Commonly known as the squash or gourd family, Cucurbitaceae is comprised of cucumbers, melons, pumpkins, squash, and gourds. Fabaceae, also called the legume or bean family, includes beans, peas, lentils, and soybeans. Solanaceae is the nightshade family, which includes tomatoes, potatoes, peppers, and eggplants.

The composite family falls within the Asteraceae category, and includes lettuce, artichokes and endives. Apiaceae is known commonly as the carrot or parsley family, and is comprised of carrots, celery, parsley, and parsnips. Beets, spinach and Swiss chard make up the beet or goosefoot family, which fall under the Amaranthaceae category. Corn is an outlier, and is in the grass family, or Poaceae.

Soil health in the garden

Crop rotation also allows horticulturists to manage their soil fertility and balance nutrients used by certain families of plants.

“Some crops are heavy feeders of nutrients and can deplete the soil of major nutrients,” Hillock said. “Vegetable crops in the same botanical family tend to use the same type and amounts of nutrients from the soil.” 

Horticulturists can actually use the plants they sow to correct and improve their soil health, nutrients and productivity by planning smart crop rotations.

“Cover crops that are nitrogen-fixing are ‘givers,’ which means they return nitrogen to the soil,” Domenghini said. “Alternating between feeders and givers keeps the soil fertile.”

For example, Hillock said members of the gourd family tend to utilize more nitrogen from the soil and members of the onion family tend to utilize a greater percentage of potassium than other plants. In contrast, members of the bean family can help add nitrogen to the soil. 

“By rotating the crops planted in the area, you can even out the loss of different nutrients and give time for nutrients to replenish,” he said.

Additionally, Domenghini said each family has a unique root system, which impacts the soil differently. For example, some members of the carrot and nightshade families have deep root systems that can break up compacted soil and access water and nutrients deep in the ground.

The onion, composite and grass families often possess a shallower root system that cannot reach far into the soil, which is why rotating these families with different root systems is a good plan.

Pest and disease control

Rotating these families can also reduce pest and disease pressure in vegetable gardens—the bane of just about every gardener. Insects and diseases are the most common detriment to vegetable production, and they can be difficult to control without pesticides.

“Rotating where vegetables are planted is an excellent way of keeping harmful soil organisms to a minimum,” Hillock said. “Soil-borne diseases, soil insects, nematodes, and toxic chemical residues tend to collect and build up in a given area.  As these detrimental factors increase, crop yields decrease, it is necessary to rotate the location of vegetables each season.”

Hillock said there are some pests that are host specific and others that can be general pests. He said an example of family-specific pests include the cucumber beetle and downy mildew in the squash family. Some host-specific pests include corn earworm and armyworms in sweet corn. Tomato fruit worm, hornworms, fusarium, and early blight of tomato are usually host-specific to tomatoes.

Domenghini said another benefit of crop rotation is the pests and diseases that are common to one plant family will not have access to a host plant after overwintering, which reduces the risk of them multiplying the next season.

Understanding all the plant families and how best to rotate them can become complicated without proper planning. Hillock suggested gardeners follow either a 3- or 4-year rotation plan. For the 3-year rotation, he suggested planting high feeders such as tomato, corn or squash; the next year plant low feeders such as carrot, spinach or beets; then in the third year, plant givers such as beans or peas.

In a 4-year rotation, Hillock recommended seeding plants in the nightshade family; the next year plant a member of the gourd family; the third-year plant legumes and in the final year of the rotation, plant members of the onion family. Once the rotation has come full circle, it’s time to start over.

“Any system can be used for crop rotation, provided the same plant family is not in the same location for at least three or four years,” Hillock said. “When creating a crop rotation system for your garden, remember that multiple plant families can be planted and rotated together in the same bed. No system will fit all your needs perfectly.  They may include vegetable species you don’t normally grow, or they may not give enough space for plant families you grow extensively.”

 Maintaining accurate and complete gardening records is crucial for planning crop rotations. Hillock also recommends taking notes of pests to help plan the next season.

“I prefer a hard copy garden journal with a calendar to keep track of planting dates and a map to identify the location of each crop,” Domenghini said. “There are digital resources as well, but a hard copy is easier to carry in the garden in my opinion.”

Lacey Vilhauer can be reached at 620-227-1871 or [email protected].

(Photo by Greta Hoffman via Pexels.)