Crop Rotation  

Basics

An allotment usually has relatively large beds of crops, each hosting plants of one family. Growing the same crop in the same bed year after year causes 2 problems:

• an ideal environment in which the pests and diseases for that vegetable will thrive;
• and the crop makes the same demands on the same specific nutrients it needs.

Put the two together and you have a recipe for epidemics sriking down even more sickly plants.

• Rotation is essential - the KISS principle, just keep the crops moving!   Leave at least a year, or better a 2/3 years gap, before a crop returns to the same bed.
• Set aside an area for the "permanents" - the fixed beds for asparagus, comfrey, fruit bushes, herbs, rhubarb, and strawberries.

Know your crops strengths and weaknesses.

• Rotation applies to vegetable/plant families, NOT to individual crops.
• Think about how susceptible your crops are to soil-borne disease, bugs and pests.
  • Some crops "must have" rotation, as they are VERY susceptible to disease and pest damage - potatoes and brassicas are obvious examples of crops which should not return to the same bed for 3 to 4 years.
  • Some crops "are keen on" a rotation - the onion family (unless you have white rot); and the carrot family.   Leeks are probably the least susceptible of all the onions, so they are quite flexible - and can fit in a number of places (mine go in after early potatoes).
  • Some crops "are generally not that choosy - but it's worth humouring them" - peas and beans.
  • And some, bless their cotton socks, are just "eager to please", and can go anywhere - beetroot, the leaf-beets, spinach, lettuce, the squashes and cucumbers, sweetcorn, salsify and scorzonera.
• Some crops benefit the following crop.
  • Beans and peas fix nitrogen - so let nitrogen-hungry brassica follow them (possibly in the same season);
  • Potatoes don't like lime, so follow them with liming in the winter; next season, plant the crops that like lime most (brassica, or beans/peas);
  • Roots dig deep and break up the soil - so follow them with potatoes;
  • Peas and beans like the rich deep dug soil left behind after the potatoes;
  • Brassica like a firm soil, so don't follow potatoes very happily;
  • The onion family are generally happy in the firm soil left by the brassica.
• Working out all the permutations gives an "ideal" 5 or 6 year sequence like this -
  • Year 1 - Beans/peas,
  • Year 2 - followed by Brassica,
  • Year 3 - followed by Onion family,
  • Year 4 - followed by carrots/parsnips,
  • Year 5 - followed by potatoes, (add lime in winter),
  • and back to the beginning
• Think of winter treatments -
  • Digging in manure in the winter before the potatoes;
  • Adding lime before the peas and beans;
  • Adding compost before the brassicas;
  • Growing a winter cover of green manure as preparation for the onion, and roots crops.