In simple terms, crop rotation is a system by which vegetables of a similar character do not follow one another on the same piece of ground year after year. Vegetables can be classified in all kinds of ways, the botanist will do so by means of natural orders; the chemist might do so by means of the manures they particularly desire; the gardener can do so by, say, their root systems - deep-rooting crops versus shallow-rooting crops; crops that tend to have the same type of manure. The biologist might put crops into groups according to the diseases and pests which attack them. So vegetables can be classified in various ways, and it is as well to look at any classification very broadly.
It would be unwise to attempt to lay down hard and fast rules as to the way that rotational cropping should be carried out. Likewise, no one could say that unless you carried out such a system your vegetable garden would be a failure or that using a system will automatically produce first rate yields.
The two problems with growing the same (or similar) crops in the same area year on year, is that the nutrients in the soil become unbalanced and that pests and diseases which are attracted to the crop can increase in the soil.
By changing the position of the crops, the nutrients can remain balanced (as different groups of crops require different nutrients) in addition soil borne pests and diseases are reduced as they are not given the chance to build up year after year.
One point of using the particular groupings of crops, is that the treatment of the soil is very similar and over the period of the rotation, the condition of the soil is maintained by the use of the various soil preparation used.
In this scheme the vegetable land is divided up into three areas for:
So plot 1 has root crops growing on it the first year, brassicas in the second year, and everything else growing on it the third year. The simple plan below shows the idea.
Year 1 |
Year 2 |
Year 3 |
|
Plot 1 |
Roots |
Brassicas |
Else |
Plot 2 |
Brassicas |
Else |
Roots |
Plot 3 |
Else |
Roots |
Brassicas |
root crops carrots, parsnips, beetroot, salsify etc. |
brassicas cabbage, savoys, cauliflower, broccoli, sprouts, turnips |
everything else potatoes, celery, leeks, peas, beans etc. |
Permanent Crops Herbs Asparagus rhubarb etc. |
In this way crops that need similar treatment and have the same kind of requirements have been grouped together. In addition deep rooting crops alternate with shallow rooting vegetables. As far as possible crop "families" are kept together. For this reason we put turnips in with the cabbage family, as they are closely related and get the same diseases and pests - notably club root.
A three-year rotation is simple to use, but it is not very easy to fit in all crops. Growers are apt to wonder where to put such things as celery and leeks, for instance, but these can be used as dividing lines between the areas if necessary - and so can runner beans or peas, if desired. In some ways, a four-year rotation has its advantages.
Here the land is divided up into four areas, and the vegetables are divided into four groups.
The crops left out are either the permanent crops that must have a place all to themselves, so that they are not disturbed, or plants like artichokes that grow very tall and so need growing at one end of the garden. Crops like parsley and chives, which make excellent edgings, and catch crops, like radish and lettuce, that can be grown almost anywhere, fitting in as they do where convenient.
Year 1 |
Year 2 |
Year 3 |
Year 4 |
|
Plot 1 |
root crops |
brassicas |
potatoes |
pulses |
Plot 2 |
brassicas |
potatoes |
pulses |
root crops |
Plot 3 |
potatoes |
pulses |
root crops |
brassicas |
Plot 4 |
pulses |
root crops |
brassicas |
potatoes |
root crops carrots, parsnips, beetroot, salsify etc. |
brassicas cabbage, savoys, cauliflower, broccoli, sprouts, turnips |
potatoes potatoes, celery, leeks etc. |
pulses |
Permanent Crops Herbs Asparagus rhubarb etc. |
Using the crop rotation system to its fullest advantage will help to rotate the systems of manuring and cultivation, and will save time and labour in the long run. Not only this, but many have found that crop rotation also save money.