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April 3, 2010 / Malcolm Dalebö

How to Practice Crop Rotation

With the Easter break fast approaching most allotment holders use the long weekend to start the years growing. If you haven’t used crop rotation before, then a few basics may be of interest.

If annual vegetable crops are grown in the same place year after year, there is a tendency for soil borne pests and diseases to become a problem, and for plant health and vigour to decline. To avoid this it is good practice to move the crops around the growing area. This is known as rotation. We have created permanent paths and beds on our allotments and this makes it very easy to rotate our crops.

Why use crop rotation?
Moving crops around helps to stop the build up of pests and diseases, which are found in the soil.

  • Plants need nutrients in different amounts and take them from different parts of the soil.
  • Changing the crops in an area means that nutrients in all parts of the soil are used.
  • Families of vegetables often need similar nutrients (food). Keeping families together means that crops get the best growing conditions.
  • Some plants have dense foliage (leaves which are close together and lots of them). These plants help to stop weeds growing. Changing from plants that do not have dense foliage, to those that do the next year, will help to keep the weeds down.
Pest and disease control

Plants which belong to the same family are grouped together when planning a rotation. Related crops are prone to the same soil-living pests and diseases. Moving them around in an organised rotation helps to prevent the build up of problems. Basically this means that all the plants from the potato family would go in one area and all the plants from the carrot family in another, as so on.

Nutrient requirements
Plants need nutrients in varying amounts and take them from different levels within the soil depending on the species and root depth. Varying the plants grown in a specific area helps to make best overall use of the soil.

Soil treatments
Crops vary in the soil treatments that they require. When a crop rotation is used, crops that require the same soil treatments are kept together as much as possible. This helps to ensure that they have the best possible growing conditions. It also means that over the course of the rotation the whole growing area will receive the same treatment.

  • Manure and compost—add these to greedy feeders such as potatoes, leeks, brassicas and marrows. Do not use on carrot, parsnip and beetroot.
  • Lime—if necessary to increase pH, add to cabbage family section in autumn before planting; this helps discourage clubroot. Keep away from potatoes, where it could encourage scab.
  • Leafmould—can be used anywhere, but particularly beneficial before root crops because it conditions the soil. 

Weed control

Some plants have dense foliage like cabbage and lettuce, these are good at suppressing weeds because they stop light reaching the soil. Others, such as onion and carrot, do not. Alternating plants with these different growth habits helps to keep weeds under control.

How long should the rotation be?

The longer the rotation the better, but the usual length is 4 years. This means that crops return to their original site after 4 years. If the soil is already infected with persistent problems such as eel-worm or clubroot, try to extend the rotation of susceptible crops even further.

How do you plan a rotation?

You can find examples of crop rotation in many gardening books. However, you can design your own by following these steps:

  1. Make a list of all the vegetable types and number of plants that you want to grow.
  2. Group the plants together in botanical families. The chart below shows you which plants belong in which families.
  3. Draw a plan of the growing area. Divide into equal sections. You need as many sections as the number of years you want the rotation to last. So for a four year rotation you need four sections. 
  4. Work out which crops are going in which area. Families should be together, but if you have more than one crop for an area, then choose plants with similar growing needs. 
  5. Keep records—of what actually happens, not just what you planned. Use this information when planning for next year


One Comment

Leave a Comment
  1. crop rotation chart / Jun 24 2010 11:46 am

    Very useful and detailed information.I will try it in my allotment.

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