Crop rotation

 

crop-rotationThe principle underlying crop rotation is that there should be a considerable gap in time between plantings of veggies from the same family in the same place. This helps stop particular diseases building up and also gives the soil a rest from particular burdens placed on it.

Veggies can be divided into the following 8 ‘groups’ (most of which are families or sub-families):

  1. Legumes (beans, peas, etc).
  2. Brassicas (broccoli, brussel sprouts, cabbage, cauliflower, kale, mizuna, pak choy, rocket, etc).
  3. Alliums (garlic, onions, etc).
  4. Roots (beetroot, carrots, celery, parsnip, etc).
  5. Cucurbits (cucumber, pumpkin, rockmelon, zucchini, etc).
  6. Solanums (capsicum, chilli, eggplant, potatoes, tomatoes, etc).
  7. ‘Anywhere’ (basil, coriander, lettuce, radish, silverbeet, spinach, etc).
  8. Perennials (asparagus, globe artichokes, rhubarb, etc).

Perennials are not relevant to crop rotation – they should be planted elsewhere. The ‘anywhere’ group are also not relevant – just plant them wherever and whenever you have gaps. So, the ideal is a 6-bed, 6-year rotation for the other 6 groups. If you have fewer beds, then you have to do one or more of three things:

  1. Combine some things: so, for example, plant alliums and roots in the same bed.
  2. Omit some things: so, for example, never plant brassicas.
  3. Plant a cool season crop (e.g. brassicas) followed by a warm season crop (e.g. solanums or cucurbits) – or vice versa – into a single bed over the course of a year.

You then have to decide the order of how a bed should change over time. A principle here is that heavy feeders should, where possible, alternate with light feeders. So, for example, legumes (light) – brassicas (medium) – alliums (light) – cucurbits (heavy) – roots (light) – solanums (heavy).

Finally, you have to choose whether the annual rotation should be in Spring or in Autumn.

For a longer discussion of crop rotation, read Angelo Eliades’ article.

  One Response to “Crop rotation”

  1. I have seen the detailed recommendations and rationales for crop rotation in many sources. My question is, ‘does anyone know of any scientific, controlled studies of crop rotation as it applies to vegetable gardens (as opposed to big agricultural operations doing acres of a crop and using green manures in off seasons)?’

    I would love to believe this theory but the only controlled study I know of was that of Charles Dowding, English market gardener and author. And his results contradicted the need for rotation. Anyone?

    P.S. Please don’t repeat the rationales, I know why it is supposed to be useful. It’s just that often we find that our beliefs are not correct.

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