Practically every gardener has heard of this (probably something they were taught in middle school history class, like me). But do they really know what it means? If they know anything on the subject, it's probably that pest problems can be reduced by consecutively planting vegetables from different families, but there's more to it.
1st there are several benefits to crop rotation:
1. Growing multiple varieties of plants at once is more maintainable by fewer people (the small farmer or avid gardener), because the plants needs are timed differently. All plants don't need to be planted or harvested at once.
2. Improved soil structure: root depth and dug in plants at end of harvest change soil structure in various ways
3. Improved soil nutrition: some plants add nutrients, others move nutrients around, and others just consume nutrients
4. Improved disease, weed, and insect control
5. Reduced dependence on expensive pesticides and fertilisers
6. Reduces soil erosion
7. Unexplained benefits: Some plants just simply grow better following other crops and the reasons aren't completely understood
2nd, it's important to know the plant families:
| Family | Common names |
| MUST HAVE ROTATION | |
| Crucifer (Brassica) | Arugula, bok choy (petchay), broccoli, brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, mustard, radish, rutubaga, turnip, watercress |
| Solanaceous (Nightshade) | Eggplant, potato, pepper, tomato |
| KEEN ON ROTATION (excluding leeks) | |
| Allium | Chive, garlic, leek, onion, shallot |
| Umbelliferae | Carrot, celery, cilantro, dill, fennil, parsnip, parsley |
| LESS FUSSY | |
| Aster (Daisy) | Artichoke, chamomile, calendula, dandelion, echinacea, endive, lettuce, marigold, sunflowers, tarragon |
| Chenopodiaceae | Beets, chard, spinach |
| Cucurbit (Gourd) | Gourds, cucumber, pumpkins, squash, zucchini |
| Legume | Beans, peas, clover, peanut, soy |
| Poaceae (Grasses) | Barley, corn, millet, oat, rice, rye, sorghum, sugarcanem wheat |
| ??? | |
| Convolvulaceae | Cassava, sweet potato, taro, water chestnut, yam |
| Malvaceae (Mallow) | Cocoa, cotton, okra |
| Tetragoniaceae | New Zealand Spinach |
| Valerianaceae | Mache |
3rd, there are several aspects to consider with crop rotation:
- Stretch it out over as many years as possible with as many different vegetables are possible
- This becomes easier the larger your garden is and the more parcels you can divide it into
2.GREEN MANURE:
- Rotating in a green manure is beneficial
- Examples: mustard greens, legumes, clover, vetch, alfalfa, buckwheat, oats, rye-grass, barley
3. COMPOSTING:
- some prefer same year composting
- others prefer prior year composting
- when composting is scarce, green manure can be substituted
- manuring helps offset (but not necessarily eliminate) the damages of negative preceding crops)
4. PLANT SEQUENCING IS IMPORTANT:
- Peas and beans are considered "nitrogen fixing", "green manure" adding good structure and nitrogen to the soil (nature's fertiliser). Most plants perform well after it, especially corn since it's a heavy nitrogen feeder.
- Negative preceding crop: Most plants don't like being planted after carrots, cabbage, beets, or chard
- Deep rooted plants: assist in pulling nutrients from deep in the soil up into shallow sections of the soil. They tend to assist in breaking up compacted deep soil.
Shallow rooted plants: benefit from being planted after deep rooted plants. - Corn, peas, and beans don't suffer the same effects after negative preceding crops.
- Corn and brassicas are heavy nitrogen feeders
- Brassicas don't perform well in loose soil and tend to pack the soil.
- Potatoes tend to loosen the soil. They don't like lime.
- Brassicas and legumes like lime.
- Peas and beans like being planted in loose soil.
- Onions are happy to be planted in firm soil.
- Potatoes perform well after corn.
- Cleaner crops - perform well against weeds. So well in fact, they reduce weeds for the subsequent crop planting. Examples include potatoes, sweet potatoes, and squash.
- Root crops perform well following "cleaner crops" since they aren't good competitors with weeds
- Tomatoes prefer to not rotate in that they like to always be grown where tomatoes have grown before. Doesn't mean they don't benefit from a cover crop in the winter or lots of compost though.
