Why Do We Practice Crop Rotation?

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Each plant has its own nutritional needs and different plants draw nourishment from different layers of the soil. As a result, growing the same plant in the same place can lead to an imbalance of soil constituents and even the depletion of some, along with an increase in parasites, weeds and diseases. In most instances, it is a good idea to wait for three to five years before growing the same crop in the same place again. You can reduce this period, or even ignore it entirely, for vegetables such as spinach and lettuce, which have a short growth cycle. On the other hand, extend the period for crops such as strawberries and asparagus where the plant itself remains in the same position for several years before being replaced, with an annual harvest of just its fruit.

There are three key rules of crop rotation:

The First Rule involves rotating plants according to whether they are grown for their roots, leaves, flowers or fruits. On a single plot of land, grow ‘fruit’ plants the first year (nitrogen- fixing), then ‘flower’ plants, then ‘leaf’ (nitrogen- hungry), and finish with ‘root’ plants. So, for example, you could plant squash, courgettes, maize and French beans, followed by cauliflowers, broccoli or green manure (phacelia, lupins, clover) which would not be cut until the flowering stage; then cabbages, spinach, lettuces and leeks, and, finally, potatoes, celery, beetroots, onions and carrots. You could achieve several rotations in the same year – for instance, green manure could precede or follow a crop. In addition to the rotation of the different crops, it is also important to bear in mind which plants grow well together.

The second rule is not to grow two plants of the same botanical family one after the other.
The main botanical families are as follows:
• Chenopodiaceae: beetroot, spinach, Swiss chard.
• Compositae: artichoke, cardoon, chicory, endive, lettuce, dandelion, black salsify,
Jerusalem artichoke. • Cruciferae: all types of cabbage, cress, mustard, turnip, radish.
• Cucurbitaceae: cucumber, marrow, courgette, melon, pumpkin.
• Leguminosae: broad bean, French bean, lentil, alfalfa, pea, clover.
•Liliaceae: garlic, asparagus, chive, shallot, onion, leek.
• Umbelliferae: carrot, celery, chervil, parsnip, parsley.
•Solanaceae: aubergine, capsicum, pepper, potato, tomato.

The third rule concerns the amount of manure a crop needs. It is good practice to follow a crop that requires large amounts of manure with one that requires little or none.
• Crops requiring large amounts of manure: aubergine, celery, cabbage, spinach, fennel, maize, leek, pepper, potato, tomato.
• Crops requiring little: garlic, chervil, cress, shallot, broad bean, French bean, corn salad (lamb’s lettuce), onion, radish, lettuce.
Other crops fall between the two extremes, requiring an average amount.

• 7 Oct, 2010
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