Beans and Peas fit into a rotation of 3 or 4 or 5 years.
Beans and Peas are legumes, that is, they are members of the Leguminosae plant family. These plants are able to make use of atmospheric nitrogen as a food. They can therefore grow in soils that lack the nitrogenous salts which most plants need.
The area where you have grown your beans and peas can be planted the next year with vegetables from the brassica family, such as cabbages, broccoli, kale, etc. See chart below. If it is possible for you to arrange your growing area in 4 sections, you can plant each group of vegetables in a different piece of ground each year for 4 years. Well designed crop rotation is the key to good organic practice. It helps to control the build-up of pests and diseases, and helps to maintain soil health and structure. Your production of vegetables will be sustainable over the long term.

1.  POTATO FAMILY – Potatoes, Peppers, Tomatoes, etc.
2.  BEAN AND PEA FAMILY – Broad beans, French and Runner beans, Peas, etc.
3.  BRASSICA FAMILY – Broccoli, Brussels Sprouts, Cabbage, Turnips, Swedes, etc.
4.  ONION FAMILY – Garlic, Leeks, Onions, Shallots, etc.
5.  UMBELLIFERAE FAMILY – Carrots, Celery, Parsley, Parsnips, etc.

This would be a 5-year rotation where the groups are moving up. (Year 2 would have Beans and Peas where the Potatoes had been.)

If only 4 beds are possible (for a 4-year rotation), then put the Onions in the same bed as the BEANS AND PEA FAMILY. If only 3 beds are possible (for a 3-year rotation), then in addition put Carrots in with the POTATO FAMILY.

Note the position of Swedes and Turnips – although they are roots, they are in the BRASSICA FAMILY.

Salad crops (also Radishes, Swiss Chard, Sweetcorn, Spinach, Courgettes, Pumpkins, Squashes, etc.) can fit in anywhere. Quite good to sow some lettuces after an early Pea crop, and in the shade of Climbing beans.

The most important means of combating pests and diseases is by good cultural practice. Thorough preparation of the soil before planting or sowing will ensure that plants are given a good start. Composting and liming may be needed, depending on local soil conditions and the requirements of the plants. Most plants will benefit from a regular supply of water, especially if dry spells of weather coincide with critical stages in the plants’ growth, such as germination, bud formation, flowering and fruiting.
Mulching the soil surface with well-rotted compost, grass clippings, green manure clippings, or some similar layer of organic matter, will help to retain soil moisture, as well as providing some nutrients and suppressing weeds.
Seeds should be sown at the correct time, taking into account local conditions, because if they are sown prematurely or too late, the plants may fail to thrive. The reason for this is that each variety is sensitive to a particular soil temperature and to light levels. Sowing at the optimum time for each variety will ensure that they get established and growing on as sturdy plants. Similarly, germination will be poor if the seeds are sown at the wrong depth. The rate of sowing is also important because sowing too densely would result in seedlings that are thin, weak, and susceptible to disease as they would compete with each other for water, nutrients and space.
Note that practising Crop Rotation will not be all you have to do to give plants enough nutrients. It is necessary to put into the soil an equal amount to what is coming off the land in terms of a crop.