Crop rotation means moving vegetables around the garden to maintain soil fertility. By rotating crops from one spot to another each season—or even in the same season, you can preserve and even boost nutrients in the soil. Differing crops use different amounts of soil nutrients and a few crops add nutrients to the soil.
How Crops Affect the Soil
Some crops are heavy feeders; heavy feeders include tomatoes, broccoli, cabbage, corn, eggplant, beets, lettuce, and other leafy crops.
Some crops are light feeders: light feeders include garlic, onions, peppers, potatoes, radishes, rutabagas, sweet potatoes, Swiss chard, and turnips.
Some crops are soil builders: soil builders include peas, beans, and cover crops such as clover.
Rotating these three groups of crops makes the best use of nutrients in the soil.
Simple Crop Rotation
Simple crop rotation would plant heavy feeders in a dedicated planting bed the first year, followed by light feeders in the same bed the second year, followed by soil builders the third year. This rotation presumes there are separate planting areas big enough for all of the crops you want to plant in each of the three rotation groups.
If you have more than three planting beds and grow a large number of vegetables you can dedicate more than one bed to each group each year and still maintain the rotation.
Small Garden Crop Rotation
Crop rotation in small gardens can be difficult; let’s say you only have one or two planting beds. In that case you can still rotate crops simply to differing spots. You can follow a tomato with a bean one year after the other. Or you can replace a heavy feeding crop such as broccoli grown in the spring or fall with peas in the spring or beans the next summer. You can also replace a heavy feeder with a green manure cover crop that feeds the soil; cover crops that feed the soil include dwarf white clover or hairy vetch.
Adding plenty of aged compost to planting beds before the season starts, after harvest, and as a side dressing during the growing season is another way to boost or replace nutrients in the soil, but that is not crop rotation.
Crop Rotation by Harvest Groups
Crop rotation by harvest groups is a simple rotation strategy: rotate leafy crops, root crops, and fruiting crops. Harvest group rotation is not a precise crop rotation method (for example, peppers are light feeders and tomatoes are heavy feeders, but both are fruiting crops—but it is an easy way to group plants and to remember the rotation from one year to the next. A simple three-year crop rotation divides crops into their harvest groups:
- Leafy crops—lettuce, spinach and members of the cabbage family such as broccoli, Brussels sprouts, cauliflower
- Root crops: carrots, turnips, parsnips, potatoes
- Fruiting crops (flowering crops): tomatoes, peppers, eggplants, cucumbers, squash
Into this mix you can add cover crops to follow fruiting crops. Because fruiting crops are almost all summer crops—tomatoes, peppers, squash, melons, eggplants, they finish harvest in early autumn and their planting area can be replanted with a winter cover crop such as winter rye or fava beans. In spring, the cover crop is turned under and leafy crops can be planted to continue the rotation. This rotation would look like this:
- Fruiting crop
- Cover crop
- Leafy crop
- Root crop
Crop Rotation by Plant Family
Crop rotation by plant family is perhaps the most traditional way to rotate crops though it can be difficult in a small garden of just one or two beds. In the plant family rotation, crops from the same family are not planted in the same spot any more often than every three years.
Crop rotation by plant family not only maintains soil fertility but also is the best way to avoid attacks by pests and diseases; specific pests and diseases tend to attack plants from the same family. By rotating plant families, pests are not easily able to find the plants they want to attack.
Notable vegetable plant families
- Squash family: cucumber, zucchini, winter squash, melons (heavy feeders)
- Cabbage family: arugula, broccoli, Brussels sprouts, cabbage, collards, kale (heavy feeders)
- Tomato family: tomatoes, peppers, eggplants (mostly heavy feeders)
- Bean family: beans and peas (soil enrichers)
- Lettuce family: endive, sunchokes, artichokes (heavy feeders)
- Carrot family: celery, parsnips, parsley, fennel, cilantro (mostly light feeders)
- Onion family: onions, shallots, leeks (light feeders)
- Spinach family: beets, spinach, Swiss chard (light to medium feeders)
Rotation by plant family will take some planning; you can match up light feeders to rotate with heavy feeders and separate the two with the soil builders.
Crop rotation by family is discussed more thoroughly in this article Crop Rotation Planning.