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PHOTO: Dwight Sipler/Flickr
You cannot be gardening for long before someone, somewhere, insists you rotate your crops. It seems at times the go-to, catch-all answer for whatever problem you may have. For this reason, a small gardener with limited space may soon find themselves asking “Yeah, but is it really that big of a deal?”
Fortunately, we have miles of studies from which to draw that conclusion. Many people have researched the effects of crop rotations (or a lack thereof) to give us all—from the backyard gardener to the 100-acre farmer—an idea of what the effects might be if we don’t.
1. Yields Will Decrease
Yields are how much useable material you get from a given plant, and though the studies often done on crop rotation are geared toward large conventional farming, the lessons are the same. Take for instance this report from the Pennsylvania State University’s extension service:
“The yield benefits are often overlooked.”
In their study, corn following soybeans will often yield up to 20 percent more than continuous corn on the same field. When following corn with corn, however, yields went down every year.
The Noble Foundation Agriculture Division also found an interesting result in one of their studies on peanuts. They did a one-year rotation of cotton followed by a one-year rotation of two different varieties of peanuts and saw an increase in yields of 1,185 pounds per acre.
So perhaps throw in a little diversity when you rotate your crops—two different varieties of peanuts, say—and see even better results.
2. Diseases & Pests Will Proliferate
The majority of plant diseases live in soil, and nothing will quite destroy your yields like diseased plants. Crop rotation, however, breaks up the cycle. Or as it is succinctly put in The Organic Gardeners Handbook of Natural Insect and Disease Control (Rodale, 1996), “Many garden pests survive the winter and can reinfect a crop if it is grown in the same spot year after year, However, if the suitable host plant is absent, the pest starves.” This is a fairly simple concept, yet gravely important.
Like diseases, pests also overwinter in soil. Although a cabbage moth may still fly all over your garden even if you rotate your crops, it may help with other pests that come from the soil. From the Rodale Institute’s Ultimate Encyclopedia of Organic Farming (Rodale Books, 2009):
“Colorado potato beetles like to eat potato plants, but they also enjoy feasting on tomato leaves and eggplant foliage. Since these beetles overwinter in the soil, if you plant eggplant in the spot where you grew potatoes the year before, you could be inviting a beetle problem for your eggplant from the day they’re planted.”
Same could likely be said for flea beetles and other ravagers, so be mindful to rotate crop families, not just crops, as you figure out your growing plan.
3. Weed Pressure Will Increase
In his excellent piece, “The Role of Crop Rotation and Weed Management,” Charles L. Mohler makes a point few other researches have: that weeds can be managed through crop rotation. Rather, weeds can become a problem without it. He describes how using cover crops between plantings can suppress weed pressure and how allowing certain beds to go fallow (letting whatever grows to grow) then killing it can greatly reduce weed populations.
But perhaps the most important point he makes is that slow-growing, weed-prone crops—winter squash, pumpkins, carrots, onions, melons—should be followed by fast-growing, easily weeded crops. Planning to follow these often vining crops in a “rapid succession” of quick crops like spinach, lettuce or radishes will help to knock back any weed seed that may have resulted.
Indeed, if you’re considering the possibility of having to fight some weeds in your crop rotation, you may already be one step ahead of the game.
4. Nutrients Will Be Depleted
Maintaining healthy soil depends greatly not just on what is added to it, but on what is taken away. Plants are generally classified as light, medium or heavy feeders in reference to their nutritional needs (generally nitrogen). Broccoli and corn, for example, are heavy feeders; peppers are a medium feeders; and lettuce is a light feeder. To maintain healthy soil, a heavy feeder should not be followed by another heavy feeder. If you don’t rotate crops with their mineral and nutrient needs in mind, you will soon find your soil less productive.
Creating a crop rotation plan can seem like a lot of work—and indeed, it can be! But with a little effort put into your garden strategy at the start of a season, you’ll be well on your way to growing a healthy, abundant harvest that will sustain you through the season.