Crop rotation

Avoid pest and disease build up and manage nutrient levels in your patch by planting vegies in a cyclical pattern. PHIL DUDMAN explains how

There are some good reasons for rotating your crops. When you grow the same crops in the same beds, year after year, pests and diseases specific to those crops breed at an incredible rate. They’re just waiting in the soil for their favourite vegies to return each year, so they can jump in and carry on with the party. However, when you vary what you grow in succession, and always replace one crop with an unrelated plant, you interrupt the breeding cycles of pests and diseases, keeping their numbers down to a more manageable level.

The other main benefit of crop rotation is nutrition. Rotating your crops helps to avoid depleting the soil of key nutrients that are associated with a particular crop. If you include a green manure crop in your rotation system, then the process also helps to build soil nutrition.

There are no hard and fast rules on how to manage this. It depends on your situation, how many beds you have and what you want to grow at a given time. The following principles and growing methods will help you decide what to plant where, and when.

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The key to it all is grouping plants of similar needs. One part of this approach arranges plants according to their family. This means that legumes, such as peas and beans, are grown side by side in the same space, as are members of the Solanaceae family, including tomatoes, eggplants, capsicums, and so on.

The other key is to group your vegies according to their nutritional demands. Heavy feeders such as corn, brassicas (cabbage family), fruiting crops (tomato and cucumber families) and leafy greens perform best when planted in soil that has been freshly enriched with organic matter and fertilisers. Light feeders, including carrots, potatoes, parsnips and other root crops, onions and legumes are less needy, and are happy to follow heavy feeders to make the most of any skerrick of goodness they’ve left behind.

Legumes are one of the most welcome guests in a rotation system. They don’t ask for much and normally give more than they take. Special nodules on their roots allow them to fix and store atmospheric nitrogen, which gives them a refreshing level of nutritional independence. These stores can be shared with other crops when their roots and stems are left to rot in the soil after harvest.

This is why legumes are used in green manure crops, where they are combined with fast-growing leafy crops such as oats, millet and rye to provide additional organic bulk. Before they mature, they are slashed then dug into the soil or left on the surface to condition the soil in preparation for a crop of heavy feeders.