Crop rotation

David Hurrion explains how rotating crops can keep soil healthy, and increase crops, too.

Practising crop rotation will prevent a build up of pests and diseases on your veg plot, while helping to increase yields. Find out how to rotate your crops in our No Fuss video guide with David Hurrion, BBC Gardeners’ World Magazine.

Crop rotation involves dividing crops into different types (usually roots, beans and peas, leafy crops and ‘other’), and growing them on different patches of ground in subsequent years. David explains how plant diseases can over winter and re-infect plants the following year. He uses white onion rot as an example, which can remain in the soil for up to seven years.

David explains why moving crops in a four-course rotation is best practice. He demonstrates which vegetable plants fall into which groups, and the best order in which to rotate – leafy crops should always follow beans, for example, as bean roots lock nitrogen in the soil, which aids leafy growth. He also suggests growing potatoes in the first year, as these require a lot of soil preparation, which benefits other crops in subsequent years.

More advice on growing vegetables:

Crop rotation: transcript

Anyone who grows their own veg will tell you that it’s a really good idea to grow different crops on different patches of soil, to move them around from one bit of soil to the next from year to year. And the reason for that is to reduce the problems with pests and diseases, but also to give the crops exactly the conditions that they need so that you’ll get the best results, the best harvests from that plot of ground.

When it comes to pest diseases, things like white onion rot will last in the soil for up to seven years. So it’s a good idea to move them, move your onions around so that they don’t suffer from that particular disease. And you might not actually see the effects of that disease in the first year. It may be that it stays overwinter in the soil.

The following year, the way to overcome that is to split the crops up into different groups and then rotate them around different plots of ground from one year to the next. Let’s have a look at that. So the guy who actually thought this up first was a man with the really interesting name of Turnip Townsend. And I’m actually
quite proud to be from Norfolk because he was a Norfolk man and he worked very closely with a guy called Viscount Cook, and they developed a way of dividing up areas of ground, agricultural ground and doing what was called a three-course rotation. So dividing crops up into three different types and growing them on different bits of ground in subsequent years. Actually, you can do the same thing in horticulture, but it’s easier if you divide it up into a four-course rotation. So group the crops together by their different attributes and
then grow each of those groups of crops on a different bit of ground over the course of four years.

So let’s have a look at those different groups. The first one is potatoes. Now, potatoes are often said to be a really good starter crop for clearing up the ground. And the thing about potatoes is that they need lots and lots of moisture. So you improve the ground for them by applying lots of your own home made garden compost.
Really lovely stuff here – really gooey and moisture retentive. And the potatoes will really love that. Don’t put too much on, though, in the first few years because otherwise you might get a bit of scab. So that’s great for our potatoes on our first plot in the first year.

So then we come on to the second group and that’s root crops. Sometimes you’ll see this divided up. It depends really whether you want to grow lots and lots of onions or lots of carrots. Sometimes this group will be divided up into two. But for convenience, let’s just consider this to be one simple group – everything that grows a root
and you harvest the root. So in this instance, things like onions, leeks, but carrots as well, beetroot. And also one of my favourites, parsnips. Now, they all need a nice deep soil, but they need it free draining, particularly if you’re going to grow things like onions. And so it’s always worth adding to the soil for those crops, before you plant them, some coarse grit or some very coarse sand, to the plot. Put a layer over the surface, dig it all in and that will increase the drainage. So you’re adapting each of the soil plots to grow the particular type of crop that you’re growing.

Then you come onto the next group, which is a really interesting group because you don’t need to do a lot of soil preparation for these other than perhaps to dig a little bit more organic matter into the soil if you’ve got very, very dry soil. And that’s the legumes, peas and beans, all sorts of beans, broad beans, French beans and runner
beans. They are what’s called legumes and that means that they have little nodules on their roots, which means that they can fix nitrogen from the atmosphere and make their own plant food. So apart from moisture  retention, they don’t need much else in the way of fertiliser because they do it for themselves. So group those together into one plot and you’ll get best results from them.

And then the last group in this four courses is the brassicas and brassicas are leafy crops. And surprisingly, it includes things like swede, but also cauliflower, cabbages of all sorts. Also, Brussels sprouts are in there as well. And they need a soil that’s been enriched for previous crops, is reasonably well drained, but actually has no more organic matter added to it, because if you add lots of organic matter for those leafy crops, then they become blown. The hearts of them don’t really set properly and they’ll run to seed. So they need very little other than a top dressing of a really good fertiliser. Now you can use organic fertiliser, but what a lot of people use is Growmore – that’s the standard basic fertiliser – and that needs to be raked in. Just to give the leafy crops something to really get their teeth into and carry on growing. So there’s our four basic groups and they all need their own separate soil conditioning. But then you come on to this last basket here, which are what I would loosely term, summer crops, and they don’t really benefit from being rotated around in this rotation at all. You can just fit these in here and there where you have space. So you say you’ve got an early crop of, say, broad
beans in one particular part of your plot. Then you could follow on with lettuce just to fill in the gap after that, after they’ve been harvested. So these summer crops don’t need specific soil conditions. Just grow them where you can fit them in. So let’s take a bit of time now to lay these out in the different plots that I’ve divided up here and see how they’ll look in the first year.

So plot one, potatoes in the first year. Lots of organic matter dug into the soil and then, whether they are main crops or first earlies or whatever sorts of potatoes, they all get grouped together into the same plot because they need plenty of space. Plot one. Plot two is gonna be our roots. So onions, beetroot, carrots, all those things just in here in plot two, conditioned with a bit of extra grit to improve the soil. Plot three, and remember that we’re going in a rotation, so we’re not jumping over to the other plot. Plot three. It’s gonna be our legumes. So, beans and peas all go together in one plot. Again, they need quite a lot of room. And then, plot four is our Brassicas and this doesn’t need anything adding to the soil other than a bit of general purpose fertiliser. And then you
come to the summer crops and remember that they can just be fitted in amongst the other crops. When you’ve got some space. So that’s your tomatoes (outdoor tomatoes), lettuce, squashes, courgettes, all those sorts of things. I’ve just put those in the middle just to show you. They don’t need planting in the middle. They need spreading around in the rest of the plot.

So that’s year one. Let’s have a look and see how the rotation works over the next four years. Year one. Year two. Year three. Year four. And if you can remember that long ago, we’re back to where we started. So that’s crop rotation, how you move different groups of vegetables around from one plot to the other, so that you get the best results and you minimise pests and diseases. Simple.