Crop Rotation... Easier Than You Think!

This month we're planning what we want to grow and where to plant our chosen crops. We always practice CROP ROTATION on our plot. Crop rotation is a simple system for planting annual edible crops that reduces the risk of diseases building up in the soil, and improves soil condition.

Crops are divided into five groups, four that are planted in rotation, and one group that doesn't place heavy nutrient demands on the soil, and doesn't harbour any specific diseases, so can be planted anywhere, anytime.

The four rotation groups are Brassicas, Legumes, Roots & Onions, and Potato Family:

You plant Brassicas where Legumes were the year before, Potatoes where the Brassicas were the year before, Roots & Onions where Potatoes were the year before, and Legumes where the Roots and Onions were the year before. 

The fifth group includes sweet corn, courgette, pumpkin, squash, marrow, cucumber, watermelon, sorrel, lettuce, spinach, endive, chicory, French and runner beans, peppers, aubergine, and Oca/New Zealand yams. These plants don’t place heavy nutrient demands on the soil, and don’t harbour any specific diseases, so can be planted anywhere you have room. However, it still benefits the crop to move them around now and again.

Crop rotation looks like this:

	Year 1	Year 2	Year 3	Year 4
Bed 1	Brassicas	Potatoes	Roots	Legumes
Bed 2	Potatoes	Roots	Legumes	Brassicas
Bed 3	Roots	Legumes	Brassicas	Potatoes
Bed 4	Legumes	Brassicas	Potatoes	Roots

Before you plant Legumes, add plenty of organic matter (well rotted manure is ideal). The next year you will plant Brassicas in the bed that just had Legumes. The Brassicas will love the leftover nitrogen from the manure and Legumes, but you should test the pH and add lime to the soil before you plant your Brassicas to counteract the acidity of the manure, as Brassicas can get clubroot if the soil is acidic. Aim for a pH between 6.5 and 7, you only want to make slight adjustments. The next year the bed will host Potatoes, which will enjoy the remaining nitrogen from the manure and legumes, but potatoes like slightly acidic soil and can get scab if the soil is too alkaline. For best results add plenty of potato fertilizer and then check the soil pH again and adjust if necessary before planting your spuds. The final year of rotation is Onions and Roots. Root vegetables don't like a lot of nitrogen in the soil as this causes roots to fork and deform, which is why this crop is planted furthest in time from the Legume crop. Roots and Onions still need nutrients, so a low nitrogen feed like Blood & Bone or NPK 1-2-2 or similar is ideal.

By the end of the four year rotation the soil is enriched and balanced, and ready to do it all again. The rotation ensures that you regularly add new organic matter and nutrients, and that you keep the soil pH regulated to keep your crops happy and healthy.

By constantly moving crops you prevent pests and diseases building up in the soil. For example, if carrot flies manage to get to your carrot crops they will leave eggs/larvae in the soil. If you planted carrots in the same soil the next year these would be infected, but because it will be 3 years before carrots are planted again in that soil, the carrot fly larvae won't be able to survive and the soil will be clean of the pest by the time carrots are planted there again.