Growers recognized hundreds and thousands of years ago, long before the advent of commercial fertilizers and pesticides, that plants performed better when the same crop was not grown in the same location during consecutive growing seasons.
Crop rotation has historically been one of the best ways to reduce insect pressure, reduce incidences of diseases, and increase plant yields.
Crop rotation also helps to restore and repair the soil. By taking a few simple actions, growers of any scale, from those with a few patio tomatoes to those managing multiple acres, can reap the benefits of crop rotation.
Crop Rotation Considerations
In general, crop rotation is most effective when two main principles are followed. The first one requires taking the approach of planting heavy nutrient feeders, followed by light feeders, followed by legumes.
Heavy feeders will take a large amount of available nutrients out of the soil as they mature and produce their fruits or mature into the vegetables they were meant to be. These include most plants that produce fruits, including tomatoes, eggplants, squashes, but also include leafy greens and brassicas like broccoli and cauliflower.
Light feeders are typically root vegetables like carrots, turnips, beets, and the like. They can follow heavy feeders since they do not require nutrients in as high a quantity to mature.
Legumes are the final step in the sequence as they repair the soil by pulling nitrogen out of the air and returning it to the soil. These include all of the bean crops and peas, but also include cover crops like clover and vetch.
The other main principle of crop rotation is to not plant crops of the same family in the same location season after season. This requires learning which plants are related, but this is relatively easy, considering that most growers – hobbyists and professionals alike – grow crops from just a few of the main families of plants:
- Solanaceous crops include tomatoes, peppers, and eggplants, but also include potatoes and tobacco too.
- Brassicas include broccoli, kale, collards, cauliflower, cabbages and Brussels sprouts.
- Cucurbits include all of the vining, large-leafed crops like cucumbers, melons, pumpkins, and squashes.
- Apiaceous plants include carrots, celery, and many common herbs.
Preparing the Soil Between Rotations
What needs to be done to the soil between crop rotations is largely unique to each site and what was previously grown. The manner of farming will also dictate what is done.
For instance, on a no-till farm, crop residues are largely left in place to decompose. Otherwise they are removed or tilled in by the majority of growers. However, if there were any diseases noted, the residue should not be allowed to decompose, but should be removed so as to not over-winter in the soil.
A layer of compost or the introduction of other organic material between crops will benefit growers regardless of what style they practice or what is grown.
In any system, weeds should not be allowed to go to seed. Between crops they should be pulled or otherwise controlled. If there has been high weed pressure or a disease, the soil should also be sterilized.
This can be done by covering with a clear sheet of plastic during months without snow cover. This will cause the soil temperature to increase high enough to kill most pathogens and weed seeds. This is not a necessary step as a matter of course, but should be done if there was disease or undue weed pressure present on the crops grown that season.
Finally, a soil analysis should be performed to know what exactly should be added to the soil between crops. The results will also help to inform the grower regarding which crops may be best suited for the next rotation as all crops have unique nutrient needs. This can either be addressed by adding the nutrients needed, or by planning your next crop layout based upon available nutrients in the soil.