Previously we have had a look at how to build a no-dig garden, how to start a vegetable garden, and also the benefits of companion planting. However, one of the basic requirements for a healthy vegetable garden and high yields is crop rotation. Crop rotation improves soil fertility and structure, helps manage diseases and insects that affect a specific plant family, and aids in weed control.

The principle of crop rotation is to grow specific groups of vegetables in a different place each year. Groups are moved around in sequence, so they do not return to the same spot for at least three years.

If you grow the same crop in the same place year after year you will get a build-up of pests and diseases specific to that crop. And different crops take different levels of nutrients from the soil - without rotation - inevitably these will become unbalanced.

Different vegetables also prefer different soil conditions. This means that when rotating the vegetables, the soil needs to be treated to suit the new vegetable. For example, onions like alkaline soil, whereas tomatoes like it acidic.

The most basic form of crop rotation is also the simplest: Never plant the same thing in the same place twice. In fact, the larger the gap between a crop occupying the same piece of ground the better. A good crop rotation plan is a sort of seasonal dance in which the crops move from spot to spot, and it helps create a garden that is constantly new and intriguing.

There are many different systems for rotating crops, some fairly crude and some quite complex, designed to ensure that following crops utilize nutrients left by previous crops. For the home vegetable grower, complex rotations are hard to manage, but a simple 3 course crop rotation is far better than no rotation at all. Better still, a four course crop rotation or even a five course crop rotation. Beyond this level most growers will be unable to control what is going where. Keeping a plan of your plot and marking in what has been planted where will prove of great value over the years because you are unlikely to remember what was planted where after two years.

You may be thinking: “My garden is too small to practise crop rotation.” But while you may not be able to rotate crops on a grand scale, you can still use the principles behind crop rotation to improve your soil and your yields. Divide a smaller garden into smaller beds in order to rotate crops.

Family	Examples	Soil requirements	Soil benefits
Brassicas	Cabbage, kale, cauliflower, broccoli, radish, swede, turnips, brussel sprouts	Leafy crops need nitrogen-rich soil; may need liming
Legumes	Pea, bean (broad, French and runner)	Well-drained but moisture-retentive; not nitrogen-rich	Fix atmospheric nitrogen in soil for future crops
Onions	Onion, garlic, shallot, leek	High organic matter; may need liming
Potato family	Potato, tomato, eggplant, capsicum	High organic matter and nitrogen (potato); no lime	Suppress weeds, break up soil structure
Umbellifers (roots)	Carrot, parsnip, parsley, celery, Florence fennel, beet root	Root crops need stone-free soil; not freshly manured; fine tilth	Root crops break up soil structure

How to rotate:

When planning your crop rotation you need to know what family the various plants belong to. Plants within the same group tend to have the same requirements and suffer from the same pests and problems.

Divide your vegetable plot into equal sections of four or more. Decide which crops to grow. Then group them, firstly following plant family (linked to pests and diseases), then soil requirements and soil benefits. Some crops may surprise you in that they fall into a rotational group you might not expect. Swedes being a root crop, you would naturally think of them as falling in with the carrots and parsnips, but they are actually a brassica. The chart showing the crops in their groups will be helpful for planning your own rotation and the enclosed example of a four year rotation plan demonstrates how it works.

Four Year Crop Rotation Plan We start the preceding winter by adding manure to the first plot, which will have potatoes planted in it. The second plot will be limed heavily to take it up to neutral and the other plots will have compost as available.
	Year 1	Year 2	Year 3	Year 4
Plot 1	Potatoes followed by lime	Legumes (Beans) followed by additional lime	Brassicas	Onions & Roots followed by manure
Plot 2	Legumes (Beans) followed by additional lime	Brassicas	Onions & Roots followed by manure	Potatoes followed by lime
Plot 3	Brassicas	Onions & Roots followed by manure	Potatoes followed by lime	Legumes (Beans) followed by additional lime
Plot 4	Onions & Roots followed by manure	Potatoes followed by lime	Legumes (Beans) followed by additional lime	Brassicas

Some crops really sit outside of the crop rotation. Those in permanent beds such as rhubarb, comfrey and asparagus obviously do not need to be considered.

Other crops like the cucurbits (cucumber, courgette, melon and pumpkin) salad greens and sweet corn can be used to fill in the gaps. But even with these crops it is a good idea not to grow them in the same place two years running if it can be avoided. If you want to give them their own section, or you decide to follow a five year rotation plan, these crops can successfully be planted together after the brassicas, before onions & roots.

With that said, please do not be too rigid in your classifications if you do not have enough room to make clear demarcations. Just make sure you keep it moving season after season.

Marc Vijverberg