For crop rotation, divide your plot into 3 or 4 large beds, as discussed in the previous section “Layout”.
Annual rotation of crops. It is absolutely essential for the health of your vegetables to rotate the different groups of vegetables in a three year or even better, a four year cycle. This is the way to avoid a build-up of destructive insects and soil infections. You will get less damaged or unusable vegetables, and will not have to resort to insecticides and chemicals to regain control of your growing conditions. It is the most important method of enabling you to grow organic produce.
When potatoes are grown on the same area of ground each year, there is a quite alarming increase in pests and diseases, such as wire worm and blight spores. These may take several years of rotation before the levels of the pests and diseases subside to acceptable levels.
When Brassicas are grown on the same area of ground each year, a build up of Clubroot can cause problems for many years.
When Alliums, the Onion family, are grown on the same ground each year, the disease white rot, will build up and cause problems for several years.
Another benefit of the rotation of crops is the more even levels of the nutrients in the soil. Some groups of vegetables take up particular nutrients, the levels of which will fall if the same group is grown on the same area each year.
Rotation, rotation, rotation, has to be the most important message to prevent the situation arising where the growing of certain vegetables is no longer viable.
Applications of added manure or lime, are more productive when applied to the right group of vegetables in the rotation scheme.
Well rotted manure, being a Nitrogenous fertiliser, is very suitable for fertilising the Brassicas. This should be dug-in during the previous Autumn.
Even though the text books advise against manuring ground to be used by potatoes and other root crops, it is frequently put in the bottom of a potato trench.
Many people have aesthetic objections to growing root crops in recently manured ground. The thought of eating crops that have been in close proximity with the manure, puts them off, particularly if the vegetables, such as carrots, are not going to be cooked before eating. Similarly, avoid growing salad crops in recently manured ground, as heavy rain may splash the manure onto them.
Lime should only be applied to the surface of the ground, if the ground is very acidicand then only once every three years. If you have any doubts, carry out a test on your soil with one of the simple testing kits. The lime is usually applied in the form of ground limestone rather than hydrated lime. It is recommended to be applied, if required, when growing Brassicas.
NB Do not apply lime anywhere near you are intending to grow lime-hating plants such as Blueberries or Cranberries. Remember that lime will dissolve in water and can seep downhill.
Do not lime potatoes as it will mark the skin.
Do not apply the lime at the same time as the manure or other fertilizers, as a chemical reaction can take place. Allow an interval of several months between applications of manure and lime, and only apply the lime to the surface of the soil. In other words, do not dig it in.
You can dig in your own well rotted compost when growing any type of vegetable. It may be of most use to retain moisture for crops such as the Brassicas and other “greens”.
There are several variations on the rotation sequence of the groups of vegetables to try and get the best use of the applied nutrients.
Different plotters grow different combinations of vegetables. The biggest group of plotters tend to use roughly equal areas of ground for potatoes, brassicas and the onion family. A further equal area is used for peas, beans, other root crops, salad crops. Other plotters grow some of the more unusual crops such as squashes, sweet corn in addition to the others. Therefore, there are several possible rotation sequences, depending on what crops you intend to grow. One possible sequence is:-
>> Potatoes and root crops + fertiliser >> manure + brassicas (cabbages, cauliflowers etc) + lime every third year or as required after soil test >> onion family (incl. Leeks) + fertilizer >> legumes (peas and beans) + general fertilizer. Fit in to the sequence, wherever you have space available, any other root vegetables and leaf vegetables.
The above sequence avoids a potential problem if you grow over-wintering Brassicas. They may well still be cropping in April and May, when you need to get the next crop planted. As a compromise, it is possible to transplant the last of the over wintering Brassicas to another bed to finish cropping.
The other big over-wintering crop, Leeks, will be finishing in April, which will leave just enough time to get the beds ready for the legumes.