Farming Gardening

Crop Rotation for Growing Vegetables

Crop Rotation for Growing Vegetables

The sight of any field, large or small, full of one type of crop ripening in the sun may now be a quintessential part of the countryside, but this mass-production method of cultivating single species has long been known to cause more problems than it solves.

For one, large plantation of the same crop makes an easy target for pests. For this reason, non-organic growers may feel compelled to spray the whole area with pesticides, perpetuating the cycle of contaminants entering the food stream. Second, Soil nutrients are depleted when the ground is occupied by large numbers of the same type of plant. This problem is compounded if the ground is again used for the same crop during next seasons – leading to soil impoverishment to an extent that use of artificial fertilizers becomes inevitable. And soil subjected to the same mechanical processes year after year will inevitably become compacted.

Scale does play a part, however underlying problem is the same. While a small-scale, backyard gardener may not employ such intensive practices as a large scale farmer, these problems may also be encountered on a smaller scale. The gardener may see a drop in plant health and productivity if crops are grown in the same spot for many years.

To avoid these pitfalls, adopting a crop rotation plan becomes necessary. The principle is straightforward enough – the same vegetables should not be planted in the same place year after year. As a system of organic gardening, crop rotation has many advantages:

  • It lessens the need for pest control and threats arising from pests
  • Reduces the spread of soil-borne disease
  • It avoids nutrient depletion in the soil

Combined with other organic methods, crop rotation offers an excellent defense against all kinds of pests and disease.

How Crop Rotation Works

Crop rotation is exactly what it sounds like – no secrets here! Simply divide your growing space into a number of distinct areas, identify the crops you want to grow and then keep plants of the same type together in one area. Now come the next year and for all the years afterwards, the plants grown in each given area are changed, so that each group (with its own requirements, habits, pests and diseases) can have the advantage of a new patch of ground.

Most crop rotation schemes tend to run for at least three or four years, as this is the number of years it takes for most soil-borne pests and diseases to decline to harmless levels. If your beds are divided into four groups, this means that members of each plant family won’t occupy the same spot more than once in a four-year period. Care needs to be taken to select the plant type as perennial vegetables such as soft fruit, rhubarb, asparagus and globe artichoke aren’t replanted each year, so they may need their own dedicated bed.

The traditional advice is well intentioned, but also flawed. It recommends that you divide crops into four main groups as follows: Legumes (bush beans, peas, pole beans, broad beans); root vegetables (radish, carrot, potato, onion, garlic, beet, rutabaga, sweet potato, shallots); leafy greens (spinach, chard, kale, cabbage, cauliflower, broccoli, spinach); and fruit-bearing(tomato, sweetcorn, cucumber, squash, pumpkin, zucchini, eggplant).

Limitations of the Traditional Method of Crop Rotation

While it is certainly beneficial to move crops around, this practice on its own is somewhat hit and miss. What’s more, such simplified groups don’t tell the whole story, as the growth habit (i.e. root, fruit, leaf etc) does not bear on the classification of the plant. For instance, although they appear radically different, potato and tomato are in fact members of the same family. According to the traditional scheme one could follow the other, but since they are so closely related, they will attract the same pests and use up the same nutrients from the soil. To avoid this type of confusion, it is highly recommended to take help of a planning tool or a local expert to devise a more sophisticated classification system. The image below is an example of a planning tool:

Crop families in the Garden Planner

Choosing among categories offer greater flexibility and allow a wider permutation of crops planted over the seasons which enhances the chances of soil replenishment. Remember the goal of crop rotation is to give a chance to soil to recover. You can sow plants from the Miscellaneous group wherever you have free space. Members of the Chenopodiaceae family, such as beets and spinach are also relatively unproblematic, and can follow most other crops.

Planning the Order of Crop Rotation

Brassicas follow legumes: Sow crops such as cabbage, cauliflower and kale on soil previously used for beans and peas. The latter fix nitrogen in the soil, whilst the former benefit from the nutrient-rich conditions thus created. Potatoes also love nitrogen-rich soil, but should not be planted alongside brassicas as they like different pH levels.

Very rich soil and roots don’t mix: Avoid planting root vegetables on areas which have been heavily fertilized, as this will cause lush foliage at the expense of the edible parts of the plant. Sow parsnip on an area which has housed demanding crops (such as brassicas) the previous season, since they will have broken down the rich compounds.

Example of a Four-bed Rotation

  1. Area 1: Enrich area with compost and plant potatoes and tomatoes (Solanaceae). When crop has finished sow onions or leeks (Allium) for an overwinter crop.
  2. Area 2: Sow parsnips, carrot, parsley (Umbelliferae). Fill gaps with lettuce and follow with a soil-enriching green manure during winter.
  3. Area 3: Grow cabbage, kale, rocket (Brassicas) during the summer and follow with winter varieties of cabbage and Brussels sprouts.
  4. Area 4: If this is your second or subsequent year, harvest the onions or leeks previously growing here over winter. Then sow peas and beans (legumes). When harvest has finished, lime the soil for brassicas which will move from area three to occupy the space next.



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