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WHEN I finally reached the top of my local area鈥檚 long waiting list for allotments, one aspect of vegetable growing that seemed daunting to me was crop rotation. This means dividing your ground into a few different patches and changing where you grow your plant varieties year on year. The intention is to reduce the build-up of pests and diseases, while also improving soil fertility.

Any guidance I could find on doing this seemed complicated, plus it required more ground than I initially had, since most of the new plot was badly overgrown. But as I learned, you don鈥檛 always have to do things by the book, and even small spaces can receive some benefits from crop rotation.

When British farms adopted a four-year crop rotation of wheat, turnips, barley and clover in the 1700s, it boosted productivity so much it led to a population boom. Key to this was introducing clover, which, being a legume, has root bacteria that can turn nitrogen from the air into compounds for the plant to use, and so boosts soil nutrients. If legume roots are left behind after crop rotation, they benefit plants grown there later.

Legumes popular with today鈥檚 home gardeners include peas and beans. Once I have harvested the pods, I cut down the stems, leaving everything in place to break down and act as a natural fertiliser for next year鈥檚 crop. If you don鈥檛 want to grow peas or beans, and have a spare bed, you can get the same benefit by growing clover over the summer, to act as 鈥済reen manure鈥�.

There are various three, four and five-year plans available to use from bodies such as the UK鈥檚 (RHS). Be guided by what you most like to eat. A simple three-step crop rotation could consist of only legumes; a nutrient-hungry crop, such as tomatoes, sweetcorn or purple sprouting broccoli; and some root vegetables.

Root vegetables, including carrots and parsnips, can reach down to deeper soil levels than crops from the nutrient-hungry group, says C茅leste Mueth, who designed an exhibit about crop rotation for last month鈥檚 RHS Chelsea Flower Show in London. Root vegetables also break up the soil, which is appreciated by the next crop. Other plants can be grown alongside these staples, depending on the available space.

For people who aren鈥檛 especially organised 鈥� like myself 鈥� the key thing is to avoid growing the same plant on the same patch two years running, says Mueth. 鈥淭here are going to be pests and diseases that can live in the soil through winter,鈥� she says. 鈥淭hey will be there, ready to attack your crop.鈥�

Twelve years after taking on my allotment, I still haven鈥檛 made a proper crop rotation schedule. But each summer, I sketch a rough outline showing where my plants have ended up, and this helps me to switch things around in the following spring 鈥� otherwise I would struggle to remember.

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