An overview of the reasons for following crop rotation and the history of crop rotation. Once you understand the principles of crop rotation the various systems and the theories behind those systems start to make sense.
Why follow Crop Rotation?
If you grow the same crop in the same place year after year you will get a build up of pests and diseases specific to that crop. Different crops take different levels of nutrients from the soil and inevitably these become unbalanced, exhausting one nutrient but leaving a lot of another. This is often referred to as a ‘sick soil’. Even the addition of fertilizers is unlikely to help since it is likely the trace elements and micro-nutrients are depleted in the same way.
Some gardeners persist in growing their runner beans or onions in the same place each year but it has been proven this is not a good idea – not every old fashioned method is good!
Rotating crops will reduce losses to pest and disease. Combine this with bettter use of nutrients and you will find increased yields from the same area of land.
What is Crop Rotation?
A basic principle of crop rotation is not to grow the same thing in the same place two years running. In fact, the larger the gap between a crop occupying the same piece of ground the better. Some pests may be present at high levels initially but a gap of three or four years will see their numbers fall to acceptable levels without a host to sustain them.
There are many different systems for rotating crops, some fairly crude and some quite complex, designed to ensure that following crops utilise nutrients left by previous crops. The simplest is a three year crop rotation but a four year crop rotation plan or even a five year crop rotation may suit you better. I have seen eight and ten year crop rotation plans but these are probably too complex for gardeners.
Who Invented Crop Rotation and When?
The concept of crop rotation goes into prehistory so answering the question of who invented crop rotation and when is not easy. Early crop rotation methods were mentioned in Roman literature, and from the Middle Ages to the 18th Century a three year rotation was practised by farmers including a fallow year.
Then a four year rotation came into use, promoted in Britain by Charles Townshend, Viscount in the 1700’s. Because he introduced turnips into the rotation his nickname was Turnip Townshend
Over in the USA, George Washington Carver was instrumental in introducing crop rotation into the southern states where the monoculture permanent growth of cotton was depleting the soil and increasing pest populations. By rotating with peanuts and sweet potatoes he provided the means for growing alternative cash crops and increasing yields of all crops.
By 1951 in Britain, Newman Turner was promoting an eight course crop rotation for organic farmers in his book Fertility Farming. Although out of print and hard to obtain you can read it online here
For the home vegetable grower, complex rotations are hard to manage but a simple 3 course crop rotation is far better than no rotation at all. Better still, a four course crop rotation or even a five course crop rotation. Beyond this level most growers will be unable to control what’s going where.
Some crops really sit outside of the crop rotation. Those in permanent beds such as rhubarb, comfrey and asparagus obviously do not need to be considered and some crops do not easily fit in like cucurbits – the cucumber family that includes pumpkins, marrows and squashes.
Not all Crops Rotate
These do have their place though, filling in where a crop does not fill its assigned space in the rotation. Even with these crops it is a good idea not to grow them in the same place two years running if it can be avoided.
General crop rotation plans are fine but what if you do not like onions and garlic? Or you only have a small plot and don’t bother with maincrop potatoes? Then you need to plan your own rotation following the basic principles of crop rotation.
Principles of Crop Rotation
- The first principle of any crop rotation is to have the largest possible gap between potatoes occupying the same piece of ground. The same applies for brassicas, the cabbage family.
- Keep lime away from potatoes because it increases the chances of them getting scab. Conversely, brassicas like a limey soil. So potatoes should be planted as far away from the application of lime as possible and brassicas can go in to soil that has been limed.
- Root crops such as carrots and parsnips do not want soil that has been manured the previous autumn. It will cause them to fork and split.
- Where possible, keep plants of the same family together as their requirements will be similar
Articles & Information on Crop Rotation
- Crop Rotation – History & Principles of Crop Rotation
- Crop Rotation – Plant Families or Groups for Crop Rotation
- Crop Rotation – The Three Year Crop Rotation Plan
- Crop Rotation – The Four Year Crop Rotation Plan
- Crop Rotation – The Five Year Crop Rotation Plan
- Practical Example Crop Rotation
- Planning the Allotment Plot Crop Rotation Plan – New Plot
- Planning the Allotment Plot Crop Rotation Plan – Previous Year
- Planning the Allotment Crop Rotation Plan – What Potatoes to Grow
- Planning the Allotment Plot Crop Rotation Plan – Interim Legumes
- Planning the Allotment Crop Rotation Plan – Finished!