Methods of preparing a new site
Dig the ground over as usual, removing as many perennial weeds as possible; this will be the only time that you should need to dig the land. Alternatively, cut down existing vegetation and cover it with a light excluding mulch to kill the weeds. Suitable mulching material includes black polythene, cardboard boxes opened out and newspaper (carpet is no longer organically acceptable due to concerns about the dyes and chemicals used for moth proofing). The newspaper or cardboard needs to be covered with straw, grass, hay or some such material to stop the wind blowing them away. A thick layer of straw or hay on its own can also be effective, if at least 10cm thick, with no thin patches. You may have to top-up or renew the mulch during this period as the materials rot away.
How long the mulches have to be kept on to get rid of the weeds will depend on which weeds are present and when in the season you start – but a minimum of one growing season is usually required, particularly if perennials such as couch grass or yarrow are present.
Fertilising the plot
All fertilisers and manures are applied to the soil surface at the usual rate of application. Rock minerals and other powdered materials (such as lime, seaweed, bonemeal etc.) can be lightly hoed in. With widely spaced plants such as courgettes or potatoes you may like to concentrate the compost or manure around the plants. Otherwise an overall application is preferable. Remember that you are relying on the worms to take the material down into the soil so it will take longer to incorporate than digging it in.
Growing through the mulch
If you are clearing a new site using the mulching method some vegetables can be grown through the mulch in the first year. Cut holes in the mulch and plant through it. If you intend to do this, however, you should not apply the mulch in the winter when the soil is cold or dry as it will tend to insulate the soil, keeping the cold in and the warmth and water out. The choice of vegetables to grow will depend on the thickness of the mulch. Suggestions include pumpkins, marrows and courgettes, brassicas, lettuces (through a thin mulch) tomatoes and potatoes. Potatoes are the one crop that is grown differently on the no dig system - see the description below.
Once the land has been cleared it can be kept weed free by hoeing and/or mulching. Mulching (in addition to manure and compost applied as fertiliser) is beneficial if you can find the materials, but it is not an essential part of the system. Suitable materials include straw, hay, leafmould and grass mowings.
Seeds are sown in the normal way; hoeing and raking can create a seed bed. In the short term, if the surface soil is very poor, take out a shallow drill, sow seeds as usual, and then cover with a mixture of damp sand and sieved compost or soil.
Transplant seedlings as usual, taking out a small hole to plant them into (this does not really count as digging!). Compost or manure can be placed round the seedling at planting time.
These are really the only crop that is grown in any way differently from the norm. As mentioned above, they are a good crop to grow when first clearing the land to establish a no-dig system. The procedure is as follows:
- Cut down any vegetation growing on the site. A mower is ideal for this if the land is flat. Water the ground well if it is very dry.
- Spread manure on the ground/soil surface at the normal rate.
- 'Plant' your seed tubers by laying them out on top of the manure layer at the normal spacing. It may be advisable, in a cold spring, to plant no-dig potatoes a little later; this is because if you cover a cold soil with a thick mulch it will tend to stay cold and take longer to warm up.
- Cover each row of seed tubers with a few inches of hay or old straw. Mark the rows, or leave a bare path between each row so that you do not stand on the tubers before they come through.
- Check regularly for shoots emerging through the mulch, and help through any that are pushing the mulch up, rather than growing through it.
- Keep topping-up the mulch as the shoots grow, covering the whole area, including paths.
- When the mulch is about 15cm thick and the plants are growing well, top-up the mulch with grass mowings. This will form a mat which will help to keep the mulch in place and also exclude light from the developing potatoes.
- Add more grass as necessary. Watch out particularly for blackbirds who love to pull the mulch around.
- To harvest the crop, pull back the mulch and remove as many tubers as you require. They will be growing on the soil surface. You can take out a few tubers and leave the plant to grow, as long as you replace the mulch to exclude light. If you want to harvest the whole crop it is best to remove the mulch from an area, pick up all the tubers and replace the mulch.
- Pests: slugs do not seem to be any more of a problem with this method than with any other; the mulch makes a nice damp haven for passing frogs and toads who will eat slugs. Land infected with potato eelworm would give a better crop using the no-dig method. Mice can be a problem as the tubers are so easy to get at. To avoid this do not leave tubers on the ground for too long in autumn.
A green manure is a plant grown primarily to benefit the soil. Green manure plants are normally dug back into the soil. This is obviously not appropriate as part of the no dig system. Instead, annual green manures can be cut down with a hoe or a lawn mower and the plants either left in situ or removed to the compost heap. In the case of grazing rye (the best overwintering green manure) this does not work well as it will grow again if hoed-off young, and is rather tough to cope with when older. Consequently, in a no dig system, grazing rye is only grown on a plot that is to have potatoes the following spring: the rye is cut down with a scythe, mower or shears and the potatoes planted on top as described above. The covering mulch prevents any problems with regrowth of the rye. Biennial and perennial green manures should be treated in the same way as grazing rye.
- Beds - P Pears (HDRA/Search Press 1992)
- Organic Gardening - P Pears and S Stickland (RHS Encyclopedia of Practical Gardening series 1995): pgs 38-41.
- Gardening with Green Manures - a Garden Organic Step by Step leaflet, available from the Organic Gardening Catalogue.
- Our online guide on How to grow potatoes without digging