If you are designing a garden for growing vegetables, you will no doubt already have thought about where you want to put your beds and you may have given some thought to what you will grow in each one. If you are an organic gardener and especially if you are interested in permaculture, you may have considered layers within each growing area and looked into the benefits of companion planting. However, even within a layered permaculture approach, without the straight rows and mono-crop planting structure of more traditional gardeners, you will probably still want to think about some form of crop rotation.

What Is Crop Rotation?

Crop rotation is all about limiting the chances of pests and disease by not growing certain annual crops in the same growing areas year after year. The important thing to realize about crop rotation is that it is only relevant for certain crops – perennials and certain annual crops can be grown in the same place year after year with no ill effect. It is likely that is any permaculture farm or garden, you will have areas where crop rotation is practiced (such as polyculture annual vegetable beds), and other areas where the planting remains for year after year (such as forest garden areas, orchards or perennial herb or perennial vegetable beds).

Why Practice Crop Rotation?

       - To Protect the Soil and Maintain Fertility

One of the main reasons to rotate different crops between different growing areas is to make sure that the soil maintains its fertility. Certain crops deplete nitrogen and other nutrients to quite a high degree. There are various ways in which we can return those nutrients to the soil – we have already discussed using mulches and liquid plant feeds for this purpose. We have already mentioned, also, that certain plants co-operate with bacteria on their roots which fix atmospheric nitrogen into the soil. Legumes such as peas and beans are key nitrogen fixers in a polytunnel growing system.

One of the reasons for crop rotation is to make sure that each of the growing areas in your polytunnel benefit from the nitrogen fixing properties of these legumes. After harvesting, the roots of these plants are left in place in the soil. Nitrogen left in the soil after the growing area has been vacated by these legumes will be of use to the next crop sown in the area, as well as to any plants grown in the same bed.

       - To Reduce Loss To Disease

Brassica, such as cabbage, broccoli or cauliflower, can get diseases which will remain in the soil. Moving them year on year will help to reduce the incidence of such problems. Tomatoes (and other crops in the nightshade family such as potatoes) also suffer from diseases that can stay in the soil. Growing them in the same bed year on year can lead to more such problems. Equally, since they can share diseases, it is best not to plant tomatoes just after potatoes, or vice versa. 

The brassica (cabbage family) and nightshade family (tomatoes, potatoes) are the two main plant families that it is best to include in a crop rotation plan. While there may be many other plant families included in a crop rotation scheme, it is usually these two families, along with the beneficial legumes, around which the system turns.

       - To Reduce Loss To Pests

Another reason for crop rotation is to reduce the likelihood that certain pests that have remained in the soil of your growing areas will decimate your crops. Certain pests are specific to certain types of crop – growing those crops in the same area year after year will make it more likely that you will have a problem with these particular pests.

How To Create A Crop Rotation Plan For Your Annual Growing Areas

Usually, it is best to have a crop rotation system that will operate over three or four years. The items grown will be separated into either three or four groups. Each of these groups will be grown in one of three or four areas. Each year, you will switch around the groups so they are grown in a different growing area. By continuing to rotate the groups of crops around the different parts of your farm or garden, you will ensure that you do not grow any of the groups of crops in the same part of the site for three or four years. 

Companion planting and polyculture systems can make it more complicated to work out a crop rotation system for annual crops. But even where annual growing areas are not mono-crop planting areas, it is important to rotate certain crops. You should (at the very least) try to rotate the legumes, brassica and nightshade families (tomatoes, potatoes etc.) and ideally also any annual alliums (onion family plants) that you grow between different growing areas. 

These families of plants are the most important to include in a crop rotation scheme. The legumes because they have beneficial bacteria in their root nodules which aid in adding nitrogen to the soil, the others because they are most prone to diseases which linger in the soil. 

Sit down before sowing seeds to sort out a three or four year crop rotation plan. Doing so will help you determine the best polycultures to plant, and where best to locate these over the years to come. 

Whatever shape your final crop rotation plan takes, make sure you add plenty of organic matter and organic feeds throughout the year to make sure yield does not diminish the yield as you rotate your crops, and try to make sure that you make optimal use of the space and avoid leaving bare soil or leaving a space unused for too long, as this can degrade the soil ecosystem and again, reduce your future yield.

Crop rotation is just one of the elements to consider when planning and planting your organic farm or garden.