No-dig Gardening

Andrew Astle
Wednesday, 28th August 2013

Andrew looks at the benefits of no dig gardening on the soil and the health of crops.

A method of gardening without digging occurred to me when I visited an arable farmer. He drilled crops with a Claydon direct drill. This machine drills seed in one pass. No ploughing or further tillage required. It cultivates narrow drainage channels. The method provides higher yields especially noticeable in a dry year.

Bill Mollison's Permaculture by design identifies that soil can be over cultivated leading to erosion. Uncultivated soil contains far more humus that retains moisture and nutrients. Nearly all the soil remains in its original position when narrow drainage channels are cultivated. The crop enjoys constant moisture and a comprehensive list of available plant nutrients. These are provided naturally by the bacteria and fungi present in undisturbed earth.

We dug a few plants and the root systems were full and deeply established. I have tried minimal cultivation in the past with disappointing results. When seed is broadcast onto hard ground, the roots of surviving seedlings can be stunted. Stunted roots give stunted plants. The narrow drainage channels cultivated by this type of direct seed drill are 7 inches deep and ¾ inch wide. The seed is broadcast in a band 6 inches wide above the channel.

In the garden we can replicate the minimal cultivation technique. Seed needs a fine tilth and surface drainage to successfully establish into a crop. Loose soil is brought to the surface when a narrow drainage channel is cultivated. It can be worked, sown and firmed; giving seeds the best chance of germination. Roots develop looking for moisture lower in the soil profile. They can break into the surrounding top soil that is uncultivated. Here they find worm burrows or cylinders of air left by a previous crop that has decayed. The plants get the best of both worlds. Narrow channels drain excess water; on the whole the soil profile is undisturbed.

Crops that provide a yield in the same growing season from seed in a kitchen garden benefit from bio diversity. The leaf litter, that isn't turned into the top soil, provides habitat for beneficial invertebrates. Woodlice are shredders that rip organic material into small pieces micro-organisms can break down. Deep burrowing, casting and composting worms prefer undisturbed soil. Their contribution to the crop is enormous. Worm casts are rich in plant nutrients. Composting worms break down surface leaf litter and burrowing worms introduce air deep into the soil profile. Predators such as ground beetle devour slugs, their eggs, aphids and caterpillars. The small creatures that find habitat in leaf litter and top soil are the first level on many food chains. Birds, bats, toads, shrews, newts and hedgehogs are examples of creatures that may visit your garden. They eat crop pests and deposit nutrition.

The contribution minimal cultivation provides towards slowing climate change is enormous. Four times more carbon is within the soil profile than in the biomass above it when measured across the whole planet. The carbon in soil exists within organic matter: leaf litter, previous crop stubble and humus. Glomalin found within the hyphae of mychorrizal fungi was discovered by Doctor Sarah F Wight in 1996. Mychorrizal fungi prefer to live in permanent soil. They provide nutrients to plant roots in exchange they receive carbon. Plants take carbon dioxide out of the atmosphere and turn it into carbon by photosynthesis. They give this to mychorrizal fungi that use it for energy but also store it as glomalin.

When we turn top soil we introduce large amounts of air. Air loving bacteria respond by multiplying into huge populations that need feeding. Their diet is carbon; they digest soil carbon and excrete solutions and carbon dioxide. The humus is stripped from between soil particles. The soluble substances the bacteria produce are washed away by rainfall or irrigation. Cultivated soil releases most of its carbon into the atmosphere as carbon dioxide.

The minimal cultivation technique I learned on an arable farm wasn't permaculture but it was a step in the right direction. Annual crops that are grown in soil that is mostly undisturbed, produce higher yields with less input. Nutrients released naturally from organic matter within the ground feed the crop consistently. Aphid and slug populations are restricted by predators that find habitat in the leaf litter. Fewer weeds germinate; ploughing disturbs seeds deep into the soil.

An organic garden begins beneath us. The annual crops that I cultivate with narrow drainage channels on the ground layer are surrounded by soil that structures itself naturally. A relatively small volume of soil is disturbed. If I have learnt a cultivation technique from an arable farmer; is it possible there is a hope he may be able to learn permaculture techniques and design? 

Andrew Astle wrote the book TINE: How to Garden Without Digging. This is an illustrated guide to preparing ground for all kinds of annual crops without turning the top soil over.

You can also watch Andrew's video, A garden tine saves digging tonnes of top soil over

Andrew’s website is: www.soilisalive.com

Further resources

Why not read Charles Dowding's Organic Gardening - the natural no dig way

Watch: Soil experiments: how no-dig systems prevent soil erosion

To dig or not to dig? How my allotment made the decision for me!

Or check out Charles Dowding's no dig experiments in Permaculture magazine 74, also available as a pdf

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