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"No Dig" Gardening

 

For a different way to tend your plot, have you ever thought of NOT digging it?

No Dig or (No Till) Gardening is doing just that. Growing vegetables can take a lot of nutrients out of the soil and digging gives an opportunity to add organic matter. However, questions have been asked as to whether digging is actually causing more harm than good. So, is it really necessary? Some people like the physical activity at the end or beginning of the season; they like to see clean, brown soil from which to begin growing or to shut down the plot over winter. But for those to whom digging doesn't sound so appealing, there is another way.

Research into this has provided some very strong arguments against digging and not just because it's back breaking!

(For some more information see "The Earth Care Manual" by Patrick Whitefield ISBN 1-85623-021-X and Living Earth (The Soil Assocation magazine) Autumn 2009).

To Dig?

You may inherit a compacted, infertile soil in which case, there is a strong argument for digging it over initially. If you have higher than average soil pests, turning over the soil will help predators get to them. Do remember though that by growing crops such as potatoes they are doing the digging for you. You will notice how the soil structure improves afterwards because the plant's roots open up the soil, add oxygen and nutrients. Just raking over the soil creates a great seed bed for sowing.

Or Not to Dig? That is the question;

Bed System

raised bedsIn a No Dig system, you try not to tread down the soil you want to grow on as this compacts it; forcing out air. So raised beds  are used with paths in between to walk on. The beds should be no wider  than 1.2 m (4ft) so you can reach the centre from either side and no longer than 5m (15ft) or you'll be tempted to walk over rather than round. It's not strictly necessary to put in edging because the crops can provide stability for the soil; you can compact the earth for the path and cover with straw to prevent mud in the winter. However if you have access to materials or the funds to provide some sort of paths and raised edges, these will help keep the soil tidy and raise it further off the ground which helps improve drainage and warms the soil slightly.

Some crops such as Brussels Sprouts prefer firm soil to help form their sprouts and to support the plant during the winter. So they prefer undug soil.

Healthy Soil

Plants need nutrients and moisture in the soil to grow. The nutrients will all be supplied in a healthy soil. But what is healthy soil and what do you have to do to get it?

You may have heard the term 'soil organic matter' – basically it refers to the amount of organic substances in the soil such as residues of dead plants, animals and insects plus billions of soil microbes and substances they produce. This reservoir of organic compounds give the soil it's fertility. The organic matter gives the soil its basic structure which helps plants get the food and water they need by keeping air circulating. It holds moisture and plant nutrients so they aren't lost by being washed away in the rain. It's also the lifeblood of the minute soil bacteria & funghi that help make healthy growth and prevent disease. Constant turning over over the soil and applications of chemical fertilisers and sprays disrupts this natural activity. When soil is turned over by digging the breakdown of organic matter releases methane, a potent greenhouse gas, to the atmostphere.

The less organic matter you have, the more susceptible your soil is to drought as it has less capacity to hold water. The miniscule plant roots cannot survive without water and the plant becomes stressed and more prone to disease and pests.

So the answer is to keep what organic matter you have in your soil, protect it and add to it.

Soil Improvers

Add your own home grown compost or well rotted horse manure. Grow green manures (see below) and cut them down to provide a mulching layer which is adding nutrients to the crop. Collect dead, non-evergreen leaves to make leafmould.

Not all crops have the same nutrient requirements. Lettuce for instance, has very little nutrient needs. Carrots don't grow well in ground that has been recently manured and also leeks grow very well in the soil after potatoes because they use the remains of the food provided for the potatoes. Beans and peas trap nitrogen from the air and store it in their roots and don't need additional food, so you plant these before you sow a heavy feeder like sprouts or broccoli and they use any residual nitrogen through their long growing season. 

Too much food can make plants produce too much sappy growth well loved by slugs. By having different beds for the various types of feeding requirements, we can tailor our soil improvers to each bed too and there's no need to manure the whole plot.

Don't forget inert substances like black plastic to help protect small areas from excessive rainfall and to warm the soil to bring forward the sowing times of such things as peas and beans. Make sure it's well pegged down though!

If you add high nitrogen soil improvers such as horse manure at the end of the season and there is a high rainfall over the winter, a lot of the nitrogen will be washed away. Instead, if you have a supply of manure cover the pile and add it into the planting area in February or March when planting heavy feeders such as potatoes, or later for tomatoes or courgettes. Mulch them in the summer after rain or watering with grass cuttings for example to prevent evaporation from the soil surface. You'll need to water less afterwards.

Green Manures

Whenever you harvest a large area of crops such as onions or potatoes and buckwheatare not going to immediately follow it with another crop, think about whether there is a suitable green manure you can sow to follow it and replenish the soil fertility. You will then just need to cut it down any time before it flowers and leave it as a mulch or dig it in ready for the next crop. Field beans after potatoes, grazing rye before potatoes. Investigate the different types as some trap and fix nitrogen from the air or draw it up from below and others have different uses. See the Garden Organic website for more details.

Generally speaking, Grazing Rye (not to be confused with Rye Grass) is considered to be the best overwintering green manure. It stores nutrients, improves structure and helps prevent weeds whilst continuing to grow in cold weather. It also fits anywhere in your crop rotation. It does not fix nitrogen though so is not so useful where you wish to grow heavy feeders such as brassicas afterwards. Growing grazing rye in September, cutting it down in February and leaving it for a couple of weeks before turning in will provide plenty of organic matter and feed for your potatoes. It also possesses an inhibitor which prevents seeds from germinating – so less weeds! Although don't grow it where you want to sow seeds...Autumn sown green manures can also die down over winter and provide protective cover on the surface as a Mulch.

One word of warning: Mustard is a fast germinating, fast growing green manure that is excellent for a quick, short space of time. The only thing you need to remember is that it is a brassica and so must be grown in your brassica bed in your crop rotation to help avoid clubroot, a soil borne mould that can develop when you keep growing brassicas in the same place. If you get this it can last for 20 years and severely affects plant growth, so is certainly best avoided. To help prevent this from building up in the soil don't grow brassicas in the same place for at least four years.

Mulching 

To help protect the soil surface mulches are used add to the surface, especially useful in the summer and winter.

Mulching is a lovely word to describe the act of putting some form of organic matter or other substance on the soil. Organic matter is material such as hay, straw, chopped down green manure or your own compost and other inert types which would typically be black plastic or cardboard. You will need to look out for slugs, snails and woodlice under the inert types though as they provide excellent living conditions for those pests but also for slowworms which eat them: the choice of material is up to you and depends on how often you can visit the plot to keep an eye on it.Conversely, you can put black plastic down to help attract slugs from the soil and then take it off and rehouse them as appropriate!

In the winter, cutting down a summer sown Green Manure and leaving the cuttings on the top will arrive at the same thing without having to bring in or buy mulch ingredients. It will also provide some nutrients for the crop.

Mulching under winter brassicas with your own compost will give them a natural boost of food, help cut down the weeds and protect the soil surface all in one. You can also grow white clover under there which is said to repel aphids.

And last but definitely not least:

Weeds

You will find a lot less weeds on your plot. As you are not turning the soil, fresh weed seeds are not being brought to the surface and germinating. That has been a major factor in our continuing with the no-dig way. Any that do appear can be hoed off and perennial weeds with roots just loosened with a fork, taking care not to disturb the soil too much, then just pull out the root and place the soil wedge back.

Where to start?

In the Autumn: The aim is to have the plot covered with plants or inert materials to protect the soil over winter.

Look to see if there is a green manure you can still sow - field beans where the potatoes were this year and where you plan to grow brassicas afterwards and grazing rye for the potato bed next year.

Collect dead, deciduous leaves and store in old compost bags with air holes to make leafmould for the root bed. It will take a year to rot down completely but can be used as a mulch before then. It does not provide any nutrients but is an excellent soil conditioner.

In the Winter: Cover a small area of ground with an impermeable membrane such as black plastic weighted down well, to help keep the soil dry and warm ready to sow some tender crops earlier than normal.

Mulch overwintering crops such as broccoli, sprouts, leeks to give a top up of food and protection.

In late winter cut down the grazing rye.

In the Spring:

Sow green manures eg: Mustard, Buckwheat, Clovers*, Fenugreek *, Phacelia(bees love the flowers), Tares*

*denotes nitrogen fixer or lifter

 In the Summer: Mulch after rain or watering to conserve moisture. Straw or grass cuttings on potatoes, provided no weed killer has been used on the grass.

Sow green manures in gaps; leave some Phacelia plants for the bees. Save some seeds to use next year.

If you decide to try No Dig gardening let us know what you think.

Zoe Ford October 2009

For further reading on this topic, take a look at the "No Dig Method explained" document (courtesy of the Garden Organic website).