Crop Rotation

Crop rotation is a simple idea, and free. It helps the health of your plants and improves the crop. It merely requires a little organisation.

You divide your vegetable garden into parts. I do thirds. Then you rotate your crops - that is, you plant different crops in the different parts each year. After three years, I come back to the same planting.

Why should you do this? Plants need nutrients, and they suffer from pests and diseases. The nutrients get used up in the soil, and the pests and diseases tend to build it year on year. The principle of crop rotation depends on the fact that different crops use up different nutrients and some crops even put nutrients back. Pests and diseases can also be specific on a plant type. Of course some pests aren't - snails and slugs eat a lot of different plants. And other pests are mobile - cabbage white butterflies are quite capable of noticing that you've shifted your brassicas along a bit! Some diseases are caused or made worse by climate, and crop rotation won't help there. But some pests and diseases do reside in the soil, and if you plant the same crop on the same spot year after year, these can build up.

There is also the problem of nutrients in the soil. Some crops, such as potatoes, use a lot of nutrients. Of course, you can add fertiliser and compost to rectify this, but fertiliser costs money and may be bad for the environment anyway. Excess fertliser soaks away downwards, and can end up in rivers, where they grow unwanted plants. Anyway, if you can get the plants to help you, why not! One category of plants are the legunes, beans and peas. They are useful because they fix nitrogen in the soil. Nitrogen is necessary for plants to grow, and there is plenty of nitrogen in the air, but plants can't access it. There is a bacteria (I think) which grows on the roots of legumes which can access the nitrogen, and then the legumes can get it from there. Not only can legumes use this nitorgen themselves, but if you use crop rotation, it is there (obviously in diminishing amounts) for subsequent crops. So - less reliance on fertiliser, which is cheaper, and probably better for the environment.

I have said that you should plant different crops in the different prats of the garden, but what, where? There are groups of species - I have mentioned a couple above. Legumes (peas and beans) are important, and those should be in a different part of your garden each year, to spread their beneficial nitrogen fixing. Another "group" is potatoes. IIf you grow potatoes, it makes sense to grow them together, and they will take up a substantial part of the garden. So that single crop is probably a group by itself. I remember which part grew potatoes last year, then plant them further up the garden each year, until the third year, when they go back to the bottom of the garden again. That helps me figure out the structure. The legumes are in the bit they weren't last year, and everything else fits around those two.

The more formal crop rotation specifies roots as a group. The instructions are usually "spread well rotted manure over everywhere, except the roots section, because mmanure causes roots to fork - produce divided roots". Well, bully for them! Since I don't use manure, and I've not noticed compost having the same effect, I don't make an effort for roots. Anyway, my main roots are carrots, radishes and beetroot, and that's hardly a third of the garden! Another group is leaf crops, such as lettuce and spinach, and I don't think they have any special requirements. Another group is brassicas, caaage, brussel sprouts, cauliflower, kale and so on. They can take a long time to grow, and may still be being harvested in the winter. That is not really part of the crop rotation system, but worth bearing in mind if you want a nice clear area of the vegetable bed to have a bonfire in! Then there is sweet corn and tomatoes. They take up a lot of room as well, and are one of the later crops to plant out, so you've got to leave room for them. My tomatoes get tomato blight, and I suspect that the potatoes also get it as well (this is not too silly, as they are related plants). So I try to keep the tomatoes and potatoes apart if I can, but I usually can't, as the garden fills up! I suppose that another group is the aliums: onions, shallets, leeks.

Crop rotation does tend to mean that your vegetable garden looks different from one year to the next. This is rather fun, but does mean that you need to sort out things every year, such as how big is the potato bed going to be, and where are you going to put the tomatoes and sweet corn. My general attitude is to note where the potatoes are this year, shift the legumes to a different area, and otherwise fitting in the other crops as I can.

Why am I only talking about vegetables? Well, crop rotation is necessary for crops, which you grow for use, and which take nourishment out of the soil. But they must be annuals. Perennials have to grow in the same place each year! Flowers are either perennials, or don't take too much out of the soil, and you may move them around (or they move themselves around!) each year anyway. Fruit seems to be perennials as well. You are not going to move your apple trees around, are you!