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Crop Rotation

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.

Reasons for crop rotation

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.

Three year rotation

In this scheme the vegetable land is divided up into three areas for:

  1. for root crops (carrots, parsnips, beetroot, salsify etc.)
  2. for brassicas (cabbage, savoys, cauliflower, broccoli, sprouts, turnips)
  3. for everything else (potatoes, celery, leeks etc.)

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

First year planting
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.

Four year rotation

Here the land is divided up into four areas, and the vegetables are divided into four groups.

  1. Potatoes,
  2. Pulses (i.e. the peas and beans), and in this group for convenience sake we can include our celery, leeks, onions, and shallots,
  3. Root crops (i.e. carrots, parsnips, beetroot, and unusual vegetables like salsify, scorzonera),
  4. Brassicas (i.e. Brussels sprouts, savoys, cauliflowers, turnips and swedes, kale, and kohlrabi) ; in this group may also be included spinach.

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

First year planting
root crops
carrots,
parsnips,
beetroot,
salsify etc.
brassicas
cabbage,
savoys,
cauliflower,
broccoli,
sprouts,
turnips
potatoes
potatoes,
celery,
leeks etc.

pulses
peas,
beans,
onions,
shallots

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.

Working out your crop rotation plan

  • List all the vegetables you want to grow over a season, and the relative quantities of each. Remember to include green manures.

  • Group crops together by family. 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.

    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 make 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.

  • Hungry crops, such as potatoes, should go on newly manured ground, while those that do not need high fertility, (such as the pea family), should follow on from them. Only apply manure to the area for the potatoes each year.
  • Root vegetables do not like soil too freshly disturbed, so they should not follow potatoes.
  • Peas and beans like freshly limed ground, but potatoes hate it. Potatoes are likely to be scabby if lime has been recently applied. So lime the soil after potatoes to grow peas, and do not grow potatoes immediately after peas.
  • Grow related crops together. Members of the cabbage family need netting against pests and diseases, so plant them close to one another.
  • Green vegetables that require regular watering are best kept together and away from root crops that need less.
 
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