Vegetable Gardening - Crop Rotation

Vegetable Families

Crop Rotation - Introduction

Vegetables are roughly broken into four family types, each family having its own characteristics, and each affects the soil it is grown in, ina certain way. These affects on the soil can be used to the benefit of the vegetable grower by initiating a crop rotation system, which in turn also aids the reduction of soil borne diseases and pests.

Vegetables are broken down into four groups. These are brassicas, legumes / pod crops, alliums and root / tuberous crops.

Brassicas - Include kales, cauliflowers, cabbages, brussels, calabrese, swedes, turnips, radishes, broccoli and many more.

Legumes / Pod Crops - Include french beans, peas, broad beans, runner beans, lima beans, okra etc.

Alliums - Include, spring onions, bulb onions, leeks, garlic, shallots, oriental bunching onions etc.

Root / Tuberous Crops - Aubergines, celery, potatoes, carrots, parsnips, beetroot, celeriac, sweet peppers, sweet potatoes etc.

With these groups in mind we move onto crop rotation.

Crop Rotation

Crop rotation is the system by which crops of vegetables are raised on different areas of the plot in succession on consecutive years. Simply you move the crops each season into a different area, but it gets a little more complex than that....unfortunately!

The main reason for rotation is it helps reduce build up of soil borne pests and diseases that are specific to one of the family groups. If you grow the same crop in the same place each year you will have a huge build up of harmful pests and diseases that will possibly destroy your crop.

Another advantage of rotation is that certain crops have certain effects on the ground they are grown. For example potatoes blanket the ground well and smother weeds, these can then be followed with a crop which is harder to keep weed free like onions.

Root vegetables are also good for breaking up the ground improving drainage and aeration.

The legume family fix nitrogen in the soil by means of nodules on their roots, which means it is ideal to follow legumes with a crop of brassicas, for example, that need nitrogen rich soil. Then of course after the brassicas which use lots of nitrogen you could plant root vegetables which require less nitrogen rich soils.

There are drawbacks with rotation too, for instance some diseases can remain in the ground for up to 20 years!, so a rotation system over 4 years would have little success in avoiding infection, and a 20 year rotation in most cases is just out of the question.

Infections and pests can also easily spread from one bed to another particularly when they are close together.

The other disadvantage is that you will probably require different amounts of produce from each family group so bed sizes will govern to some degree what you can grow and where.

In general though I think it is good practice to rotate as much as possible to reduce the overall risk of pests and disease.

Simple Crop Rotation

If you have 4 beds you can grow 1 family group per bed each year and rotate them over a four year period.

Example

Bed 1 - 1st - Legumes, 2nd - Brassicas, 3rd - Root, 4th - Alliums

Bed 2 - 1st - Brassicas, 2nd - Root, 3rd - Alliums, 4th - Legumes

Bed 3 - 1st - Root, 2nd - Alliums, 3rd - Legumes, 4th - Brassicas

Bed 4 - 1st - Alliums, 2nd - Legumes, 3rd - Brassicas, 4th - Root

Hope that makes sense!!

The rotation you use will depend on the amount of beds you have and the quantities of vegetables you want to grow. You will need to work out a system that best suits your requirements and your individual plot.

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