Crop rotation is the successive planting of different crops on the same land with the aim of reducing the risk of diseases and pests whilst increasing the crop productivity and soil fertility.
Plants belonging to the same family planted in the same area of soil can be prone to the same soil-living pests and diseases. So by rotating crops you’ll be helping to prevent the build up of problems and you’ll be caring for the soil by improving microbial balance.
The rotation process involves not planting crops from the same family in the same soil for at least two years (five years being ideal, although this won’t be realistic for many gardeners).
To keep things simple, here’s some popular families below:
– Chives, garlic, leek, onion, shallots, spring onions.
– Beetroot, quinoa, silverbeet, spinach.
– Endive, Jerusalem artichoke, lettuce.
– Cabbage, cauliflower, broccoli, Brussels sprouts, kale, kohlrabi, mustard, Oriental Brassicas (Bok Choy, etc.) radish, swede, turnip.
– Cucumber, gourd, marrow, melon, pumpkin, squash, zucchini.
Bean and Pea family.
– Alfalfa, beans, broad beans, clover, carob, chickpea, fenugreek, liquorice, lupin, peas, snow peas.
Agricultural grass family.
– Maize, sweetcorn.
– Capsicum, chilli, eggplant, potato, tomato.
– Carrots, celeriac, celery, coriander, dill, fennel, parsnip, parsley.
Crop rotation is not just about minimising diseases and pests. It’s also about caring for the soil.
Some crops are ‘heavy feeders’ and take lots of nitrogen and nutrients from the soil. If these crops were continuously planted in the same soil season after season, the soil would become depleted. Some crops are ‘light feeders’ and don’t require such rich fertile soils. With this in mind, we can estimate the potential level of soil nutrients and plant accordingly.
It’s good to start with a crop of legumes because they can fix atmospheric nitrogen and store it in the soil so that plants can access it. Once you’ve harvested the legume crop, allow the plant to break down into the soil. This will help add plant material full of nitrogen into the soil, which is a good thing. Legumes include broad beans, peas, runner beans and snow peas.
Now that the soil is chock full of nitrogen, planting a hungry crop would be a smart move. Some ‘heavy feeders’ include; Asian greens, cabbage, cauliflower, cucumber, broccoli, lettuce, potato, spinach, tomato and zucchini.
Grow root vegetables after you’ve grown the hungry crops because they’re great at scavenging for nutrients and can handle the poorer soil with ease. Some ‘light feeders’ include; beetroot, carrots, garlic, leeks, onions, parsnips and silverbeet.
Green manure can then be grown and worked back into the soil, adding organic matter and getting the next crop off to a good start. Continue to improve the soil throughout the process by adding manure, worm castings and compost.