The rules of crop rotation apply to plants in the same family, like tomatoes and potatoes, as plant families are usually susceptible to the same pests and diseases (unless a particular variety has been bred for resistance).
Crop Rotation Helps to Avoid DiseaseGrowing the same crop in the same spot year after year is called Monoculture. Wherever monoculture exists, pests and diseases concentrate their efforts (it’s why Big Ag farmers have to use heavy applications of pesticides and fertilizers). If Verticillium Wilt infects your tomatoes this year, and you plant tomatoes in the same bed next year, the previous season’s soil-borne Verticillium will quickly have its way with your tomatoes and will produce even more fungi in the process. But if a crop resistant to Verticillium follows the tomatoes, like broccoli or mustard, which doesn’t mind verticillium at all–the fungi diminish.
Crop Rotation Controls Insect PestsMany soil dwelling insects are fairly immobile. Take wireworms for instance. They love to feast on sweet potatoes and carrots. If you plant those edibles in the same raised bed every year, wireworms will build up in the soil and in a few seasons you’ll have a terrible infestation on your hands. But if you follow carrots or sweet potatoes with a non-root vegetable like lettuce or spinach, the wireworms will lose their food source and will be incapable of multiplying. Similarly, if aphids infest your broccoli, planting that crop again or any cole crop like Brussels sprouts or cabbage in the same bed the following year is just asking for double the infestation.
Crop Rotation Avoids Depleting Soil NutrientsThere are additional benefits to crop rotation. Yields decline if the same vegetables are grown in the same garden beds year after year, due to soil nutrient depletion. Additionally, roots which plunge to different depths each year keep the soil food web active; legumes stimulate beneficial soil microorganisms; and big, leafy greens are excellent at suppressing weeds.
Every plant requires unique amounts of nitrogen, phosphorus, potassium (N-P-K) and trace minerals. When the same plant makes repeated demands of the same patch of soil, the elements it requires become depleted and may take years to replace. For this reason, use a soil test for monitoring levels of N-P-K and composting in between crops is recommended for soil health.
3-Year Crop Rotation Plan for Vegetable GardensIf you have three or more garden beds, assign each plant family below a letter: one group to A, one to B, one to C. Grow plants from the same family together.
- 3-year, 3-bed crop rotation plan:
- 1st year: Bed 1: Family A Bed 2: Family B Bed 3: Family C
- 2nd year: Bed 1: Family B Bed 2: Family C Bed 3: Family A
- 3rd year: Bed 1: Family C Bed 2: Family A Bed 3: Family B