The aim of crop rotation is to increase long-term soil fertility by not always growing the same vegetables in the same place year after year, but instead growing different annual vegetables in different parts of the plot each year. The main benefits include: reducing the build-up of pests and diseases that are specific to certain plant families; reducing the chance of nutrient deficiencies developing in the soil as certain types of plants have different requirements; and aiding weed control as some crops with large leaves, like potatoes, suppress weed growth better than others.
Plan out which areas of the plot you will use for different groups. This will depend, of course, on how many of each type you wish to grow. Keep notes as it’s quite easy to forget what was planted where two or three years down the line. Rotate the crops so that each is followed in sequence as suggested below for a classic four-year rotation:
- Roots (carrots, parsnips, celeriac etc.) and alliums (onions, garlic, leeks)
- Legumes (peas and beans)
- Brassicas (cabbages, cauliflowers, kale, swede etc.)
If you have enough space, you could also include one or two further areas to grow green manure for a season or two (creating a ‘ley’) using red clover or lucerne for example. Some growers develop further rotations by separating roots and onions into two areas, and a further one for sweet corn and pumpkins, to the extent that it could be 9-10 years before an area is used by the same type of crop.
Crop rotation like this is easy to plan if you have a series of raised beds, or areas that can be clearly divided up, like on an allotment, but some gardens are more cottage- or forest-style, with vegetable plants dotted about here and there. This is known as polyculture with crops either fully interspersed, or grown in adjacent rows of different types (row intercropping). This has the advantage of getting further away from the monocropping-style of growing, so plants are less likely to suffer from pest build-up or nutrient loss from a concentration of one type of plant.
Obviously with polyculture like this, it’s not necessary to practice the same sort of rigorous crop rotation, but you can still bear in mind where certain annuals were grown the previous year, and try them somewhere else the year after.