GARDENER COLUMN: Effective crop rotation in the vegetable garden

I was finally able to plant in my vegetable garden May 6-7. Even though it’s just my husband and I, we plant a relatively large vegetable garden. I’m fortunate as he built eight 4-foot by 8-foot raised garden beds plus we have four medium-sized galvanized tanks filled with soil as well to plant surplus crops. Even with all of that space, it’s important to pay attention to crop rotation.

Crop rotation helps improve soil fertility and nutrient availability to your vegetables. It can also help with insect pest management and disease. Studies have shown that when crops are not rotated, crop production numbers eventually decline, primarily because of soil-borne diseases and various insect pests.

To effectively implement crop rotation, start by identifying the “groups” your crops are in – legume, leaf, fruit, or root. I’m using those terms loosely, but you’ll get the gist in a minute. Legumes fix nitrogen in the soils – think beans, peas, and lima beans. If you grow potatoes, you can plant them with the legume group instead of with the roots. Potatoes have the same issues as other nightshade plants—tomatoes, peppers, and eggplants—and could benefit from a year break in the typical rotation schedule. Leaf crops need nitrogen – think greens, lettuce, spinach, brassicas – broccoli and Brussels sprouts, and herbs. If you plant corn, put it in with the leaf crops due to it being a heavy nitrogen feeder. Fruit crops are ones that need more phosphorus: tomatoes, cucumbers, peppers, eggplant, squash, and melons. Finally, root crops are ones that require potassium. This group consists of vegetables such as beets, carrots, radishes, onions, garlic, and turnips. For my garden, my top crops are tomatoes—fruit group, broccoli and Brussels sprouts—leaf group, beans—legume group, onions and garlic—root group. I plant other vegetables, but these crops are guaranteed the most real estate in my garden.

Next, divide your garden into four equal sections. The goal is to create a four-year rotation based on each groups’ nutritional needs. The sections should be the same size and should be as large as your largest crop. For example, I plant lots of tomatoes, so I dedicate two of the eight raised beds primarily to tomatoes. I don’t plant as many onions or garlic, but when it’s time for my tomatoes to rotate into the next area, it is always large enough to hold them.

This is how the rotation works. The legume group put nitrogen into the soil and follows the root group. The leaf group is a heavy nitrogen feeder so it follows the legume group so it can use the nitrogen put into the soil from the previous year’s legumes. The fruit group needs phosphorus but can’t handle a lot of nitrogen in the soil or it won’t set fruit, so it follows the leaf group. The root group needs potassium and even less nitrogen, so it follows the fruit group. Each year, just simply rotate to the next appropriate section.

Fit your other crops into their appropriate sections as best you can. Utilize companion planting for those that don’t fit into their assigned sections, so they can benefit from another nearby crop. I plant lettuce—leaf group—between my onions, carrots, and beets—root group—as onions help deter pests such as aphids and supposedly rabbits. They also have different root depths, so they don’t compete for the same soil space. I just make sure to rotate my major crops as noted before and everything else gets fit in, just not in the same location as the previous year.

Crop rotation has its place, even in small gardens. Take some time to group your vegetables into these four main groups and start a rotation. You’ll be happy when you have fewer insect pests and soil-borne diseases, and better soil nutrient management.