Rotation of crops in the community garden

Hi all,
          Please have a read below on the importance of crop rotation in your community/garden/allotment.

Enjoy
Willie

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.

Crop Rotation - Plant Families or Groups

When planning your crop rotation you need to know what family the various plants belong to. Plants within the same group tend to have the same requirements and suffer from the same pests and problems. For example, club root affects brassicas, the cabbage family, but did you know swedes are brassicas? They look more like a root crop than a cabbage!  Blight is mainly thought of as a problem with potatoes, yet it affects tomatoes just as badly, once again members of the same family.

The list below should help you identify what crops need to go together in the crop rotation.

•Cruciferae - the cabbage tribe, formerly known as Brassicaceae from which we get Brassica. This is one of the most important crop groups in a rotation as they are generally lime loving. Because of the requirement for a high pH level, they anchor one end of the crop rotation cycle.

 The group includes:   Cabbages, Cauliflowers, Kale, Broccolis and Calabrese, Swedes, Turnips, Radishes, Landcress, Mustard

•Solanaceae - the potato family, which also includes tomatoes and aubergines. The potatoes form the anchor at the other end of a rotation as they need a fairly high level of nitrogen and prefer a slightly acid soil with a pH around 5.5. Usually manure is added to the plot the autumn before planting the potatoes.

•Leguminosae - the bean family of legumes.  Anything  with 'bean' in the name, runner, French, broad, field and peas which are one of the oldest food crops grown by man. These share a wonderful ability to fix nitrogen from the air and so provide at least a good proportion of their fertiliser requirements.

•Alliums - the onion family. Allium comes from the Latin for garlic and includes shallots and leeks.

•Cucurbitaceae - the cucurbit family includes cucumbers, marrows, courgettes and pumpkins as well as cucumbers.

•Umbelliferae - this includes carrots, parsnips, Hamburg and ordinary parsley, celery and celeriac. 

Species not listed above, like sweet corn, can be considered out of the family groups and safely intermixed with them. Salsify and scorzonera are members of the Compositae family but best considered as Umbelliferae along with the parsnips.

Leeks   Allium,   Onions   Allium,   Shallots   Allium,   Beetroot   Chenopodiaceae,   Spinach   Chenopodiaceae,   Jerusalem Artichokes   Compositae,   Lettuce   Compositae,   Salsify   Compositae,   Scorzonera   Compositae,   Broccoli   Cruciferae,   Brussel Sprouts   Cruciferae,   Cabbages   Cruciferae,    Cauliflowers   Cruciferae,   Kale   Cruciferae,   Landcress   Cruciferae,   Radishes   Cruciferae,   Swedes   Cruciferae,   Turnips   Cruciferae,   Cucumbers   Cucurbitaceae,   Marrows   Cucurbitaceae,   Pumpkins   Cucurbitaceae,   Sweet corn   Gramineae,   Beans   Leguminosae,   Peas   Leguminosae,   Miner's Lettuce   Portulaceae, Potatoes   Solanaceae,   Tomatoes   Solanaceae,   Carrots   Umbelliferae,   Celeriac   Umbelliferae,   Celery   Umbelliferae,   Hamburg Parsley   Umbelliferae,   Parsley   Umbelliferae,   Lamb's Lettuce   Valerianaceae,

 

The Three Year crop Rotation

This is the crop rotation favoured by many gardeners because of its simplicity. After taking out the permanent beds, the growing space is divided into three and handled as below.

The problem with this crop rotation system is that it assumes you will be growing a lot of potatoes and brassicas. The third of the plot left over has to cope with everything from onions and garlic to sweet corn and squashes.

Neither does it allow much time before the potatoes are back in the same bed and the lime left over from the brassicas is still keeping the pH level high for them. Having said that, it is very easy to manage and any spaces on the plot if you grow too few brassicas for example can be filled with crops from the 'everything else' group.

We'll start our rotation year in the preceding winter - just to add to the confusion. Don't  worry, all will become clear.

• Plot 1 has manure added to it and this will feed the potatoes that follow on. The nitrogen in the manure tends to make the soil more acid, which is fine for potatoes that like a slightly acid soil.
• Plot 2 has lime added to take the pH level up towards neutral (7) for the lime loving brassica family in the following year.
• Plot 3 is ignored, although a mulch with compost if available would be useful.

Three Year Crop Rotation
	Year 1	Year 2	Year 3
Plot 1	Potatoes followed by lime in the autumn	Brassicas	Everything Else followed by manure in the autumn
Plot 2	Brassicas	Everything Else followed by manure in the autumn	Potatoes followed by lime in the autumn
Plot 3	Everything Else followed by manure in the autumn	Potatoes followed by lime in the autumn	Brassicas

On heavy clay soils you will probably be digging over each winter to allow the frost's freezing and thawing action to break up the soil. With other soils it would be a good idea to sow an over-wintering green manure crop to hold nutrients that would be washed away in the rain.

The green manure can be dug into the soil in the spring to release those nutrients and improve the soil's humus level with the organic matter. On really light soils a green manure is vital to build good condition and adding the manure or the lime in early spring after digging in the green manure is suggested.

The early potatoes that come out of the ground in June and July can be followed with French beans that are not too fussy about the acidity level of the soil and will produce a crop on the same ground. If you have enough land that you are not pushing for maximum crops and you don't have club root to worry about, follow your potatoes with a green manure of mustard. The use of mustard as a green manure after the early potatoes hardens the cysts that contains the next generation of potato eelworm so preventing them from hatching. A lot will depend on your actual requirements when you set up and use a rotation plan. The important part of your crop rotation is to keep things apart for as long as possible. Keeping a plan of your plot and marking in what has been planted where will prove of great value over the years because you are unlikely to remember what was planted where after two years.

The Four Year Crop Rotation

As with the three year crop rotations and five year crop rotations, we divide our plot up after allowing for the permanent beds of comfrey, asparagus and rhubarb. In this case into four beds or areas.

We start the preceding winter by adding manure to the first plot, which will have potatoes planted in it. The second plot will be limed heavily to take it up to neutral and the other plots will have compost as available.

On heavy clay soils you will probably be digging over each winter to allow the frost's freezing and thawing action to break up the soil. With other soils it would be a good idea to sow an over-wintering green manure crop to hold nutrients that would be washed away in the rain.

The green manure can be dug into the soil in the spring to release those nutrients and improve the soil's humus level with the organic matter. On really light soils a green manure is vital to build good condition and adding the manure or the lime in early spring after digging in the green manure is suggested.

The other two plots can be split with the legumes, beans and peas taking one plot and the onion family taking the other.

Four Year Crop Rotation Plan
	Year 1	Year 2	Year 3	Year 4
Plot 1	Potatoes followed by lime	Legumes (Beans) followed by additional lime	Brassicas	Onions & Roots followed by manure
Plot 2	Legumes (Beans) followed by additional lime	Brassicas	Onions & Roots followed by manure	Potatoes followed by lime
Plot 3	Brassicas	Onions & Roots followed by manure	Potatoes followed by lime	Legumes (Beans) followed by additional lime
Plot 4	Onions & Roots followed by manure	Potatoes followed by lime	Legumes (Beans) followed by additional lime	Brassicas

If you have enough land that you are not pushing for maximum crops and you don't have club root to worry about, follow your potatoes with a green manure of mustard. The use of mustard as a green manure after the early potatoes hardens the cysts that contains the next generation of potato eelworm so preventing them from hatching.

Since the bean family tend to fix nitrogen rather than exhaust it, these go well before the brassicas. L D Hills suggested that the bean family should follow the lime with the brassicas on the second year after liming. Since most of the expert brassica growers suggest liming immediately before brassicas, you could go lime, legume, additional lime, brassica if you wish. The onions and the root crops share the last bed in the rotation. Crops like the cucurbits and sweet corn fill in the gaps. The benefit of this four course rotation is the gap between each crop, especially the cabbages and potatoes, occupying the same ground is extended and the other crops in the rotation have more flexibility in position. A lot will depend on your actual requirements when you set up and use a rotation plan. The important part of your crop rotation is to keep things apart for as long as possible. Keeping a plan of your plot and marking in what has been planted where will prove of great value over the years because you are unlikely to remember what was planted where after two years.

 

The Five Year Crop Rotation

This is the crop rotation plan I try to follow myself. I say 'try' because there are always crops that don't fit in so neatly and with those my main aim is to avoid them being on the same piece of ground two years in a row.

Potatoes; I start with the potatoes, the soil having been given a good amount of manure or compost the previous year. This reduces the need for fertilizers for the potatoes.

Green Manure; The  potatoes are followed with a green manure crop of agricultural mustard. The use of mustard as a green manure after the early potatoes hardens the cysts that contains the next generation of potato eelworm so preventing them from hatching easily.

Lime Follows Potatoes, Then Legumes

Following the potatoes, in the winter the soil is limed heavily taking the ph up towards neutral. Although the brassicas like a high pH, meaning lots of lime, L D Hills contended it was more effective the second year after application. For this reason I follow with the legumes, the peas and beans. The legumes fix nitrogen and by composting the haulm but leaving the roots in the ground, you add to the nitrogen available.

More Lime Before Brassicas

You can cover all the bases with this rotation by liming just before the brassicas as well. Now you know they will definitely have enough lime and the extra benefit of the legume's nitrogen. Ideally extra manure is added but not at the same time. This goes on in early winter and the second liming goes on in late winter or early spring. Following the brassicas, the next crops are the sweet corn and cucurbits, squashes and pumpkins, marrows and courgettes. They take up a fair amount of space so equalling the space for potatoes and brassicas. Organic growers in particular should grow as many legumes as possible. Apart from the health benefits from using them as a protein source, even if you are not vegetarian, they benefit your plot by producing lots of foliage to convert to compost and that additional nitrogen. 

Other Roots & Onions

The final group is the root crops, carrots, parsnips and turnips and the onion family. Of course it never works perfectly, but it does give a long spacing between the main crops of potatoes and brassicas.

The list below should help clarify. A lot will depend on your actual requirements when you set up and use a rotation plan. The important part of your crop rotation is to keep things apart for as long as possible. Keeping a plan of your plot and marking in what has been planted where will prove of great value over the years because you are unlikely to remember what was planted where after two years.

1. Potatoes, followed by mustard green manure and lime following
2. Legumes, peas and beans followed by additional lime if required
3. Brassicas
4. Sweet corn, squashes, pumpkins, courgettes etc.
5. Roots (carrots, parsnips) and onion family, followed by manure.

 

Five Year Crop Rotation Plan
	Year 1		Year 2		Year 3		Year 4
Plot 1	Potatoes followed by lime		Legumes (Beans) followed by additional lime		Brassicas		Onions & Roots followed by manure
Plot 2	Legumes (Beans) followed by additional lime		Brassicas		Onions & Roots followed by manure		Potatoes followed by lime
Plot 3	Brassicas		Onions & Roots followed by manure		Potatoes followed by lime		Legumes (Beans) followed by additional lime
Plot 4	Onions & Roots followed by manure		Potatoes followed by lime		Legumes (Beans) followed by additional lime		Brassicas
		Year 5
Plot 1		Potatoes followed by lime
Plot 2		Legumes (Beans) followed by additional lime
Plot 3		Brassicas
Plot 4		Onions & Roots followed by manure