In order to sustain the productivity of the vegetable garden over a number of years we must practice the process of crop rotation. Crop rotation means growing a set of different crops in a certain area of the vegetable garden each year. Crop rotation normally follows a three year cyle where the vegetable plot is divided into three areas and three different sets of crops are grown each year.
| YEAR 1 | YEAR 2 | YEAR 3 | |
| Area 1 | Brassicas | Root crops | Legumes |
| Area 2 | Legumes | Brassicas | Root Crops |
| Area 3 | Root Crops | Legumes | Brassicas |
Maintaining soil fertility with crop rotation
One reason for using crop rotation is that different vegetable crops we grow have different nutrient needs from the soil. If we grew the same crop in the soil each year, then the nutrient types in the soil that the particular crop required would soon be used up. This would lead to progressively declining crop yields each year. By rotating the crops we can balance the nutrient demands on the soil so that one particular nutrient set isn’t exhausted.
Certain crops can actually provide benefits to the soil for one of the other crop groups. An example of this is the legumes group. The roots of peas and beans actually fix nitrogen in the soil. Nitrogen is required for leaf growth and so the Brassica group and leafy greens are normally planted the in the site of last years peas and beans.
Using crop rotation to aid in pest and disease control
Another important reason for using crop rotation is that it can help prevent the buildup of pests and diseases that occur in the vegetable garden, and will reduce your crop yields by attacking your plants. The practice of crop rotation is therefore one of the foundations of organic vegetable gardening as it can reduce the need for chemical methods of pest or disease control.
If you change the crops you grow each year then plant or plant group specific pests and diseases (such as Carrot fly) will not have the same crop to attack the next year. This makes it harder for them to sustain their presence in the soil.
What vegetables are included in the three different crop groups?
| Group 1 Brassicas and leafy greens | Group 2 Root Crops | Group 3 Legumes + others |
|---|---|---|
| Cabbages Cauliflower Broccoli Kale Brussel Sprouts | Potatoes Carrots Parsnips Swedes Turnips Beetroot | Peas Beans Tomatoes Celery |
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