Crop Rotation:
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Crop rotation is simply the practice of growing vegetables in different parts of your plot from year to year in order to prevent the build up of soil-born pests and diseases, such as clubroot (for brassicas) and white rot (for onions). If for example, you grew potatoes in the same patch year after year, you would see a decline in the yield and health of the crop as the soil became more impoverished , while at the same time diseases specific to potatoes built up in the ground. However , while a degree of crop rotation is important , it isn’t absolutely essential to follow a rigid scheme – it can simply be enough to bear in mind what has been grown in each bed the year before and make sure that the same crop isn’t grown there for the next two or three years . However , well organised gardeners can find it enormously helpful to have a good scheme to follow , knowing that it will result in enhanced yields and improve the overall health of the plot.
Three , four – or five year rotations can be followed depending on how many different vegetables you are growing and how much space you have. Here we focus on a four year rotation , with vegetable crops divided into four main categories. The fifth group ‘ others’ can be planted with any of the other four.
The first step in planning a crop rotation is to make a list of all the vegetables you want to grow , then group them into the categories shown below. There are three main groups – legumes , brassicas and root vegetables – plus the alliums (onions ,shallots , leeks and garlic) and a group of ‘others’ which can be grown with any of the above to fill space. If you are planning a three year rotation , the alliums can be grouped with legumes , because they have similar needs from the soil. If, as shown , you are planning a four year rotation the alliums can be put into their own group.
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Each of the main groups has different needs from soil. Legumes require a reasonably rich soil , but more importantly, they are nitrogen ‘fixers’ ,meaning that they obtain nitrogen from the air and transfer it into the soil via their root systems. Brassicas are heavy feeders and need lots of nitrogen to thrive , so it makes sense for them to come after the legumes in crop rotation – that is they should be planted where the legumes were grown the previous year. Root vegetables don’t need much nitrogen , so they can follow the brassicas. Alliums ,too , don’t make heavy demands on the soil , so they can follow the root crops , together with other vegetables , such as lettuces, sweetcorn and courgettes , which don’t fit into any of the main categories. These are classed as ‘others’ on the plan and can be slotted in wherever there are spaces.
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The next step is to divide your plot up into the necessary sections and it will best if you draw this out to scale in order to help with planning.
