Understanding vegetable crop rotation
Story and Photography by A.J. Heinsz-Bailey
Crop rotation is truly very important. The productivity and health of even the smallest vegetable garden will benefit from this centuries-old practice. If you’re first thought is, “I’m not a farmer. This doesn’t apply to my small garden,” you would be wrong. One reason to rotate crops is to prevent the spread of diseases. Planting the same crops in the same locations allows disease organisms to build up, and they can remain in the ground for several years. Changing plant families leaves the organisms without a host and helps decrease or even eliminate undesirable organisms. One example is the nightshade family, which includes tomatoes and potatoes; both crops share the same disease problems. Late blight disease organisms can survive in potato tubers left in the ground from the previous year. If you plant tomatoes in that area the following year, they will probably get the disease. If you plant the tomatoes in a different location, the disease can be avoided.
Another way crop rotation can prevent infestations is by eliminating the food source of certain pests. Many adult pests and their offspring overwinter in the soil. Nematode infestations can be reduced by rotating crops. Leaf miners attack members of the goosefoot family, such as spinach and Swiss chard. If planted in the same space year after year, pest populations can increase rapidly, which can result in reduced harvest or even no spinach or Swiss chard. Change the location and you can ensure that the leaf miner population is limited and that your spinach harvest is abundant
Another reason to rotate crops is to improve soil health. Different plant families have different nutritional needs. Varying the crops in an area each year helps maintain the nutrient level of the soil and keep the soil from becoming depleted. Legumes incorporated into a rotation plan will replenish usable nitrogen in the soil. Some plants enhance the soil, so rotating them through the garden provides free organic soil conditioning. Examples are beans or legumes. Legumes are called “nitrogen-fixing” plants. They have nodules along their roots with specialized bacteria called rhizobia that allow them to absorb nitrogen from the air and then release it into the soil. Since legumes add nitrogen to the soil, follow them with nitrogen-loving leafy crops, which will reduce the need for fertilizer.
Now that you know why you should rotate your plantings, it is time to develop a plan. Divide your garden into different areas. A four-year rotation schedule with four planting areas is the simplest design. Review your plant families and decide which vegetables are your favorites and place them into family groups. Plant each area with the same family members. Tomatoes, peppers, eggplants, and potatoes are all in the nightshade family. Rotate these plantings each year. Allow at least three years before you re-plant the same family in a given space.
Some vegetable families grow well together. Corn can be planted with squash or beans. Onions can be planted with any group except legumes. Leafy crops and members of the cabbage family do well together. Root crops, such as beets, carrots, and radishes, can be planted as filler crops anywhere in the garden. Root crops break up the soil, so they can be followed by legumes that prefer loose soil texture.
Try to plant at least one section every year with “green manure” – a cover crop such as alfalfa or clover that you’ll till into the soil later. You could also mix in plenty of organic matter and allow the soil to rest. The cover crop will add nutrients to the soil.
After the initial plan is written down on paper, use it as a guide to make future plantings easier. Choose a method of rotation that works for your garden. Adapt the plan if you have a container garden or raised beds. Crops will be healthier, there will be fewer insects and diseases, and best of all, you should have an increase in crop production regardless of the size of your garden. Rotation is simple and worth the effort.
VEGETABLE FAMILIES
Apiaceae (carrot family): carrot, parsnip, parsley, celery
Asteraceae (sunflower family): lettuce, endive, radicchio
Brassicaceae (mustard family): cabbage, broccoli, cauliflower, brussels sprouts, kohlrabi, turnip, radish, Chinese cabbage, kale, collards, rutabaga
Chenopodiaceae (goosefoot family): beet, Swiss chard, spinach
Convolvulaceae (bindweed family): sweetpotato
Cucurbitaceae (gourd family): cucumber, muskmelon, watermelon, squash, pumpkin, gourd
Fabaceae (pea family): garden pea, snap bean, lima bean, soybean (legumes)
Liliaceae (onion family): onion, garlic, leek, shallot, chives
Malvaceae (mallow family): okra
Poaceae (grass family): sweet corn, popcorn, other corn
Solanaceae (nightshade family): tomato, pepper, eggplant, potato, tomatillo