Crop rotation
If annual vegetable crops are grown in the same place year after year, there is a risk that soil borne pests and diseases will become a problem, and that plant health and vigour will decline. A better system is to move crops around the growing area. This ancient practice, known as rotation, continues to be used today to the benefit of both soil and plants.
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 - and moving them around in an organised rotation helps to prevent the build up of problems in the soil.
Some plants are better than others at suppressing weeds. Alternating crops helps to keep weeds under control.
Soil treatments
In a rotation, crops that require the same soil treatments are kept together as far as possible, the whole growing area receives the same overall treatment over the course of the rotation.
- Manure and compost - apply where greedy feeders such as potatoes, leeks, marrows and brassicas are to grow. Do not use on carrots, beetroot, parsnips.
- Lime - if necessary to increase pH, apply to the cabbage family section in the autumn before planting; this helps discourage clubroot. Keep away from potatoes, where it could encourage scab.
- Leafmould - can be used anywhere; particularly beneficial before root crops.
Planning a rotation
Rotation plans in gardening books tend to be based on standard British crops - brassicas, legumes, potatoes and so on. Even if you don't grow any of these, you can still devise an effective rotation that suits you and your crops. The usual length is 3 or 4 years - so crops return to their original site after a break of 3 or 4 years. If the soil is already infected with persistent problems such as eelworm or clubroot, try to extend the rotation of susceptible crops even further.
- List all the veg you want to grow over a season, and the relative quantities of each. Remember to include green manures.
- Group plants together by botanical family (see chart). Some relationships may seem a little unlikely, but if you were to let all the plants flower, their family likeness would soon become clear.
Draw a plan of the growing area. Divide it into equal sized sections according to the number of years you want the rotation to last - try 3 or 4 to start with. A "section" may be made up of several discrete areas, or you may have several "sections" in a large bed. Distribute your crops within these sections. (see example).
The first rule is to keep families together; if a section is to hold more than one family, try and keep those with similar growing requirements together. Using a bed system can planning a rotation easier. You may also find it helpful to write crops on to pieces of those moveable sticky note pads. You can then play around until you find a combination that fits.
- You may find, for example, that the quantity of potatoes you had planned, might be too large to fit a section. In this case, reduce the number of plants rather than abandoning the rotation.
- Short term crops such as lettuce and other salads, early carrots and beet can be fitted in on any plot.
- Keep records - of what actually happened, not just what you planned! Use this information when planning the next year’s cropping.
Further reading
- Beds Pauline Pears, (HDRA/Search Press 2004)
- Soil Care and Management Jo Readman, HDRA (Search Press 1991)
- The Vegetable Garden Displayed Joy Larkcom, RHS 1992)
- Planning the Organic Vegetable Garden Dick Kitto (Thorsons, 1986)
- Our step-by-step booklet on Green Manures, available from The Organic Gardening Catalogue (£1.35p).
- Our Getting Started with Green Manures Guide
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