I have a confession to make. Crop rotation on a small plot has always rather baffled me. On a big plot it makes sense - on a big plot you can afford to leave a patch of ground empty in preparation for a later crop, or to sow a green manure in the middle of summer just for the heck of it - but on a small allotment where you want to make the most of every space all year round, it can be a real juggling act trying to get your potatoes out early enough for your purple-sprouting broccoli to go in, or clearing your onion patch in time to sow beans and corn, or figuring out what on earth to grow after you've harvested your squashes as late as October - and who uses exactly the same amount of space for every crop group anyway??
Traditionally, the main groups in a crop rotation are potatoes and roots, brassicas, beans, and 'other veg'. The potatoes are manured to enrich and slightly acidify the soil (preventing scab), heavy-feeding beans follow in the nicely broken-up ground after the potatoes are dug, then (often after an application of lime,) leafy brassicas to make good use of the nitrogen the bean roots accumulate. Then, presumably, you throw sweetcorn, cucurbits, tomatoes, leafy greens and everything else in together after that. Sounds simple enough, but questions abound. Do you grow swedes with the root crops or the brassicas? Aren't tomatoes in the same family as potatoes? Cucurbits take up way more space than anything else! And aren't you supposed to avoid manuring carrots?
I don't know, maybe I overthink these things - maybe I'm just too keen to abide by all the rules and to do it "right". But I think, after eight years on our allotment, I've finally cracked it!
This is partly thanks to slimming down the number of crops we grow on the allotment anyway - we don't grow onions and garlic due to white rot spores in our soil, and we prefer to keep salad leaves and quick-ripening summer crops like French beans, courgettes and tomatoes at home so we can pick them more regularly. On the allotment we grow the lower-maintenance stuff: potatoes, squashes, root veg, broad beans, leeks, and a limited amount of winter brassicas and spinach-type leaves (plus some perennials in a permanent area). We've grouped broad beans, leeks and root veg roughly together: together they take up about the same amount of space we use for more space-hungry crops (potatoes and squashes), and it means we can follow our broad beans (which finish around midsummer) with winter brassicas, thus keeping our earlier-sown swedes in the same area as our other brassicas.
Ladies and gents, I give you our brand new crop rotation plan! (Click pic to enlarge.)
This rotation also allows for two squares to be sown with green manures over winter to add high-nitrogen organic matter to the compost heap, shelter wildlife and protect the soil. Phacelia and field beans are my two favoured green manures since field beans add vital nitrogen to the soil and can be sown as late as November, and phacelia attracts lots of insects and can be sown as late as September. Following squashes with winter-hardy beans means the timing for sowing is perfect; likewise with the winter leaves following the potatoes, and the winter brassicas following the broad beans. And even though we grow most of our beans at home, our allotment soil still gets a nitrogen injection thanks to the broad and field beans. Of course, this rotation doesn't include everything and I should do my best to efficiently rotate our crops at home too, but those on the allotment are the most important ones to rotate: beans for nitrogen, potatoes which are prone to damage from buildups of slugs and eelworms, and brassicas which are susceptible to clubroot, a very nasty fungal disease.
So far it's all going swimmingly. The potatoes are out (an awesome 28kg of Kestrel and 19kg Pentland Crown!) and the winter leaves are in; two rows of chard, two rows of winter spinach and a row of fennel (there's room for more, actually - I must do that). The squashes have finished a little earlier than usual, which means we have plenty of time to clear the soil for winter beans. The leeks, root veg, celery, spring cabbages, kohlrabi and pak choi are coming along nicely and we will slowly harvest them all winter long, making the most of all our space. Brilliant!
There is one complicating factor looming, in that we are planning to clear our old strawberry and asparagus beds (not shown in the plan above) over winter and put them to new use next spring. These two areas don't really fit into the plan so I'm a bit puzzled about what to do with them (and I rather wish we could move our pond and our apple tree into one, which would help us make better use of the other!). Should we grow runner beans or courgettes on the plot again after all? Shall I expand my collection of perennials? Is it time to give in and plant some fruit bushes? Good job I've got all winter to think about it...