Small-Scale Crop Rotation: Inspired Vegetable Gardening

Crop rotation, or the practice of moving plant families around in your vegetable garden, can help you control harmful microorganisms and boost your yields.


| January/February 2013



Raised Beds

High raised beds like these allow the soil to drain well, even over clay.

Photo By Fotolia/Alix Marina

The traditional vegetable garden is somewhat predictable for some homesteads. Not in terms of yield — no way in terms of yield — but often predictable in the sense that the sweet corn has its place, the tomato cages seldom move from year to year, the gourds have their corner, and we ultimately find ourselves digging potatoes in the same place every year. Though that system can be fulfilling and wonderful, consider a little crop rotation moving forward, and you might be pleasantly surprised; amazed even.

One of the easiest ways to get more out of your soil is to rotate plant families from one season to the next, as best you can, so that related crops are not planted in the same spot more often than every three years or so. This rotation will help the soil maintain a healthy balance of nutrients, organic matter and microorganisms.

Take potatoes, for example. In the course of a season, the fungi that cause scabby skin patches may proliferate, along with root-killing Verticillium fungi (which also damage tomatoes and eggplant) and tiny nematodes that injure potatoes. If you plant potatoes again in the same place, these pathogens will be ready and waiting to sabotage the crop. Rotating the space to another unrelated crop deprives the potato pathogens of the host plant they require, diminishing their numbers as they migrate or die. Think of it as playing keep-away with your veggies. Most pests and diseases prefer plants of the same botanical family, but cannot hurt unrelated crops (see the sidebar at the end of this article, “Rotate Your Families: The Nine Main Groups”). 

Field trials in Connecticut and Europe indicated that rotated fields produced roughly 66 percent more potatoes than their counterparts. Far fewer spuds fell prey to disease when they were consistently rotated with other crops. According to a seven-year study from Ontario, Canada, you could expect similar gains if you rotate your tomatoes. Compared to eight different rotations with other vegetables or cover crops, tomatoes had the most to gain by consistent rotation. Snap beans are another good candidate for rotation. In a recent study from Cornell University, snap bean production doubled when beans were planted after corn rather than after snap beans.

In addition to interrupting disease cycles, rotating crops prevents the depletion of nutrients. For example, tomatoes need plenty of calcium the same way beans and beets crave manganese. The exact benefits of rotations will vary according to the crops in the cycle. Broad-leafed greens are great for suppressing weeds, and the deep roots of sweet corn do a good job of penetrating compacted subsoil. Nitrogen-fixing legumes often take no more nitrogen from the soil than they replace, and their presence stimulates the growth of beneficial soil microorganisms. But in some situations, the “rotation effect” defies easy explanation. For example, we don’t know precisely why potatoes tend to grow well when planted after sweet corn, but they do.

The subject of crop rotation can get complicated so fast that it’s no wonder we are tempted to cheat. What if your garden is like mine — a collection of a dozen permanent beds that are planted with 20-plus different crops in the course of a growing season? Not only will rotations seriously improve your yields, but because you have several separate ‘patches,’ they’re easy to implement. On the other hand, these small ‘patches’ need careful rotation to stay healthy. When researchers at Pennsylvania State University tracked early blight of tomatoes grown in the same place for four years, early-season infection rates (measured when 5 percent of fruits turned red) went from 3 percent in the first year to 74 percent in the third. When they tried the same monoculture maneuver with cantaloupes, symptoms of Alternaria blight (early blight) appeared earlier and earlier with each passing season.





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