Crop rotation is the practice of not growing plants where similar plants grew the previous year.

Crop rotation prevents the build up of pests and diseases and optimizes the use of soil nutrients. Plants from different “families” need different amounts of nutrients and their root systems also penetrate the soil to different levels. To simplify, we try to alternate between leaf crops and root crops. Leaf crops tend to be heavy nitrogen feeders with fairly shallow root systems. Root crops usually require more phosphorus and potassium and need deep soils in order to grow properly.

Different plant families also prefer different soil pH levels, so the rotation plan includes planning lime applications.

PH preferences are: Higher pH (limed) Lower pH (acidic)

Brassicas, Solanum Salad, Potatoes, Spinach, Root crops, Squash, Alliums, Peas & Beans

Brassicas & Leafy Greens: Include cabbage, broccoli, cauliflower, Brussels sprouts, mustards, kale, kohlrabi and Chinese cabbage. Also lettuce, radicchio, spinach, and other leafy greens.
Legumes & Alliums: Peas, beans, lentils, chickpeas, and soy. Alliums include onions, shallots, leeks and garlic.
Cucurbits & Solanums: Include cucumbers, melons and Summer & winter squashes, as well as the solanums like peppers, eggplants, and tomatoes.
Root Crops: Potatoes, carrots, parsnips, and beets all love acidic soil.

To optimize space, practice a four year rotation. In year one, prepare the bed for this four year cycle with a healthy application of lime in increase the soil's pH - making it less acidic. Grow brassicas and any of the leafy greens. These will have good crunchy texture and strong cell walls from the minerals in the soil. Year two, the Legumes and Alliums are still using the residual lime. Year three, the squashes and Solunums are enjoying the slightly more acidic environment. In year four, potatoes and other root crops are grown when there is the least amount of lime left and the soil is wonderfully acidic for them.

There are many times, however, when we have just one spot where we can grow tomatoes or where the trellis for peas is permanently in place. If you are short of rotation places, seriously consider moving the soil instead of the plants. It’s a bit of work with the shovel and wheelbarrow but well worth it when you see the improvement in the health of your plants.