Crop Rotation

Rotation - A Brief Discription
A system in which vegetable crops are grown in different sections (courses) of a plot on a minimum four-year cycle to minimized the build up of soil-borne pests and diseases in one section (see further information below).

Read on for more details:
The importance of roation for vegetable crops
The basis of production using organic principles is a healthy, biologically active soil, with good organic matter reserves, that can supply nutrients for the production of crops and vegetables without artificial chemical nutrients.

This involves providing the soil with materials that can be broken down by soil micro-organisms to release crop nutrients for uptake by the plants.

A balanced cropping rotation incorporating legumes is the basis for nutrient provision in all cropping plans based on organic growing principles (legumes are a class of plants that host nitrogen-fixing bacteria on their roots). See below.

In an ideal world, there should be as long a gap as possible between the growing of a member crop of the same group of species in the same soil but extending the rotation by adding additional courses to the rotation, increases the cost of the new kitchen garden. It involves installing a fifth bed or combination of beds for example to accommodate the increased gap between species from three to four years or more.

Detailed information is given below and in the growing guide provided with each Living Leaves® Garden Kit.

The group names for each course are:

1. the potato family & compatible plants

2. legumes (members of the pea and bean family) & compatible plants

3. the brassica family (members of the cabbage family) & compatible plants

4. the onion family & roots

5. There is a fifth group of plants which can be grown 'Anywhere in the four course rotation'.

Plants fall into this group because they are less susceptible to plant pests and diseases which in any case are host specific to those crops.

The four courses follow each other in the sequence shown in the table, so that the classes of crops in any course only return to the same growing area after a gap of three years. The diagram shows that the first course growing in bed 1 (in this case early potatoes) in the first year of the rotation will not be grown in Bed 1 again until the fifth year (a gap of three full years).

The reason why legumes (member crops of the pea, bean and clover families) are so important is quite simple. Legumes in association with specific bacteria present in the soil are able to take atmospheric nitrogen from the air and convert it into nitrogen plant nutrient for the succeeding crops. In fact legumes are the main source of naturally occurring nitrogen nutrient in the soil in systems based on organic growing principles. Such provision can then be supplemented by adding extra organic materials containing nitrogen to the soil including. In general terms the main ones are:

> Well rotted farm yard and poultry manures

> Composted plant materials and crop residues

> Green manure crops

It may be possible while sticking to organic growing principles, to utilise limited quantities of manure from a conventional farm or stables, providing it is not from an intensive system using artificial chemicals and provided that the animals that produced the manure have not been fed drugs or GMO feed. All manures should be properly composted.

Additional materials that may be used include :

> Rock minerals and liming materials to adjust pH (acidity) level

> A range of processed organic wastes and by-products (GMO free)

> Seaweed and seaweed products

The main functions of rotations are :

> To maintain soil fertility and supply crop nutrients

> To provide weed, pest and disease breaks

Rotation of salad crops
Although salad crops are less susceptible to the build up of disease in the soil, where possible it is a good idea not to grow the same crop in the same soil without at least half a year's gap during which you grow a non related species.
The exception is where salad crops are grown continuously in one small bed e.g. in a Living Leaves® Table Bed outside the kitchen door. In such cases it is feasible to change the soil in the bed after a period, if you experience deterioration in plant health.

Details of the Living Leaves® four course rotation, use of organic fertilisers and pest control recommendations are included in our Growing Guide, one of the benefits of membership of the Living Leaves® Growing System.

Adding a fifth course to your Living Leaves® four course vegetable rotation.
If you wish to extend the gap between the growing of the same crop from three years to four, it is easy to do so by adding a fifth course to the rotation.

Our advice is that though this is desirable agronomically, it is generally acceptable on cost grounds not to do so. It may be sensible if you wish to grow main crop potatoes (harvested after their skins are set in September/October) rather than early potatoes, to extend the gap for this crop by an extra year to four. The reason for this is that the crop can suffer from the build up of a microscopic free living soil nematode which in very high numbers will affect the vitality of the potato plants (This pest is not harmful to humans). The pest will be removed with the potato haulm when harvested in June or July (early potatoes) but may build up in the soil if the plant is allowed to grow on through August and September. Potato haulm should always be burned in any case rather than disposed of on the compost heap to avoid the carry over of potato blight (a fungal disease which kills the foliage) and the cysts of these nematode pests.

To leave a gap of four years, the main crop potatoes should be grown in a separate rotation of its own. This can be achieved by adding a fifth bed (the main crop potato bed or beds) to your layout and then adding an extra course to this separate rotation after the fourth, involving a green manure crop or crops that do not fall into one of the four categories potatoes, legumes, brassicas and onions & roots See the Livmg Leaves® Growing Guide for details.

Companion Plants
The principle of companion planting is that growing specific combinations of plants together brings mutual benefits in health and vigour, and a consequent reduction in pest and disease problems. The following artical from dgsgardening about Companion Plants shows some of the thought applied to using them.

This is a cultural system where two or more plants are grown in close proximity in order that they may provide some form of benefit to one or all of them. This could be to deter or act as a decoy for pests and diseases, or improve growth and flavour. Usually it is the aromatic foliage or flowers of the companion plant which deters the pest or draws it away.

The improvement in growth or flavour is probably due to the companion plant adding some of the micronutrients or the roots may support microorganisms which improve their uptake. In the case of legumes they fix nitrogen, and White Clover is included in some grass seed mixes, for this reason - it is also drought resistant so greens up quicker than grass when used in lawns.

Some plants exude protective chemicals (allelochemicals) from their roots or foliage which can deter pests, eg. African Marigolds produce thiopene which repels nematodes so it makes a good companion plant for root crops which are attacked by these pests. This is given the title Allelopathy.

Tall plants can provide shelter for lower-growing ones and create a microclimate allowing them to thrive where they may not normally grow. This may also protect them from pests

Beneficial insects can be attracted to a cropping area by planting something which they use as a food nearby, eg. adult Hover Flies feed on nectar,but their larvae feed on aphids so planting nectar-rich flowering plants will attract them.

Marigolds and Garlic have a reputation for repelling a number of insect pests such as Aphids and Carrot Root Flies. The Mexican Marigold, Tagetes minuta or Muster-John-Henry, is an annual which grows to about 1.2 m (the species name refers to the flowers not the height of the plant). The roots have an insecticidal effect on nematodes and some effect on keeled slugs. The secretions responsible begin about 3 months after sowing and also affect the growth of Ground Elder (Aegopodium podagraria), Bindweed (Convolvulus arvensis), Couch grass (Agropyron repens), Lesser Celandine (Ranunculus ficaria) and Ground Ivy (Glechoma hederacea). It is grown as a half-hardy annual which can be planted out after the risk of frost has passed, but this does not usually give them a long enough growth period to flower and set seed in Britain. Dead heading prolongs the growth for protection purposes.

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