When you only have a small area to work with, it's really good to keep it in production year-round. And with a bit of cunning, you can easily have two crops a year from most of your beds! (Well, that is the ideal anyway - I'm still learning, and some of my crops do fail. But trial and error is what it's all about.)
I like to grow small quantities of a wide variety of veg, since there are only two of us to feed, so I currently have eight 1.2m x 3.5m beds on my little allotment, on a four-year rotation (2 beds in each rotation group). The four groups are: Onions & Roots, Brassicas & Beets, Legumes, and Three Sisters.
If you want to try it, or just find out more, click on the "Continue reading" link for all the gory details (including a spreadsheet to print out or adapt to your own needs)!
Details of plan
Onions and Roots
Onions and root vegetables like similar conditions - a well-drained but not dry soil, and not freshly manured either - and the smell of onions is reputed to keep the dreaded carrot root fly away, so they make ideal companions
Bed 1: onions and parsnips
Bed 2: garlic and carrots, followed by leeks and more carrots
Three Sisters
It's what all the cool kids are doing nowadays :) However... In our climate, sweetcorn may not grow quickly and strongly enough to support climbing beans, so the beans are best off grown up separate supports. Also, because my beds are long and narrow, I plant half of each with sweetcorn to form a block, to aid pollination, rather than having corn in one bed and beans in the other.
Beds 3 & 4: Half of each bed planted with sweetcorn, half with climbing French beans, and winter squash growing beneath everything
Brassicas and Beets
Lots of leafy veg for all-year-round superfood goodness! This group actually occupies the two beds for almost eighteen months, but that's OK because the Three Sisters group is only in the ground for about six months, so it all works out in the end. Cunning, eh?
Bed 5: Spinach and calabrese, followed by PSB and kale
Bed 6: Spring cabbage, followed by autumn brassicas and beetroot, followed by turnips and chard
Legumes
I've decided to put celeriac in with this group, rather than with its cousins the carrots and parsnips, because it likes much wetter conditions. Also I'm growing legumes in two of my rotation groups (this and Three Sisters), but broad and runner beans don't appear to suffer from the same diseases as peas and French beans, so I'm going to chance it.
Bed 7: runner beans and celeriac, followed by winter spinach
Bed 8: broad beans and peas, followed by spring cabbage (leading into brassica group, above)
Four-year plan (.xls file)
Depending on your soil and climate, you may be able to have all the beds occupied nearly all the time, by putting overwintering onions and garlic in after the three sisters finish. On heavy or unimproved soil, you could leave this as a gap for soil recovery, and just mulch well over winter.
I haven't included potatoes in my plan, as they take up a lot of space and are prone to blight on the allotment. From now on I am going to try growing them in potato barrels on the patio, which is supposed to give a big crop in minimum space. I've also omitted salad vegetables such as tomatoes and lettuce - I prefer to grow these in my garden at home, where I can water them more regularly and pick them really fresh.