As we learn more about the inter-connectedness of our environment, and look for ways to mitigate our impact on nature, there has been a growing movement towards the no dig method of gardening.

The Reasoning

Soil that is cultivated is disturbed, this means that the mycorrhizal fungi is exposed to light and air and cannot survive in these conditions. This disturbance breaks the connections between plants and fungi meaning both are poorer for the experience.

Similarly, the soil is made up of small particles of weathered rock (sand, silt and clay). The parental layer – the rock, is at the bottom, then you have the subsoil, then towards the surface you get topsoil and at the top is the organic layer. Careful cultivation can maintain these layers to an extent, but most cultivation is not careful and often brings sub-soil to the surface burying the topsoil and organic layer beneath. Topsoil and the organic layer can be used by plants to take up water, air and nutrients via their roots, so the mixing of these layers can be very detrimental to plants as well as the insects and other beneficial organisms that live there.

By maintaining the structural integrity of the soil, you can bypass the problems that can make soil less healthy and help improve the conditions for life in and on your garden. Weeds and their seeds are opportunistic and will take advantage of the conditions created by cultivation. They can grow in poorer soil structures and thrive because any competition has been removed. Nature abhors a vacuum and she will fill it in the most expedient way possible. You could say that weeds will take advantage of wounded soil before it has a chance to heal, like an infection of bacteria in a cut.

To avoid these problems the no-dig process of gardening has been established to keep your soil balanced and the beneficial organisms that inhabit it, healthy and undisturbed.

Please note that if your soil is heavily compacted enough to have created an impermeable pan this will not help, and that issue will have to be remedied first. See previous article on Clay soil.

The Practice

When creating a new bed for instance, no-dig gardening requires the use of scrap cardboard and/or a thick layer of mulch to supress weeds. It will help the stop the soil from drying out while maintaining the delicate balance of your existing soil.

Use broken down cardboard boxes with all staples and plastic tape removed. The less ink on the cardboard the better, as most inks are inorganic and not healthy for the environment.

Lay the cardboard over the grass or border to block out the light and then cover with a thick layer of mulch which will supress any weeds. Many insects will welcome the cover and their presence will help the process of breaking down the layers of cardboard and mulch, incorporating them into the soil. Worms will also aerate the soil during this process, improving the soil for drainage and encouraging root ingress. The mulch needs to be as thick as possible, 4-6 inches or more. You can plant into this layer and then mulch around the new plants but be sure to leave a small gap around the plant and not pile the mulch up against the stem as this could cause the plant to rot.

The mycorrhizal fungi will quickly spread into the cardboard and mulch layer and create symbiotic relationships with most of the plants, which will help them establish more quickly and efficiently. The fungi provide access to extra moisture and nutrients while taking a small amount of plant sugars in return. When weeds pop up they can be easily removed by hand or with careful, shallow hoeing.

The Upside

Less time spent watering, weeding and feeding. Depending on the mulch used it can provide some nutrients which will be washed in by the rain. The worms and other organisms will take the composting plant matter down into the soil. They will also aerate it helping to avoid waterlogging and compaction. The humus created as the mulch breaks down holds moisture which is evenly released to the roots. In short, the ecosystem is maintained and protected. So, you spend less time and effort to get plants which are healthier and can provide higher yields of flowers, tasty fruit and vegetables.

The best time to start a no-dig bed is in the Autumn. Weeds are dying-back, most crops are finished. The soil is still warm and generally moist and all the beneficial organisms are still active.

DO NOT start a no-dig bed when it is hot and dry as you will make any water absorption even more problematic.

Add extra layers of mulch in Autumn or Spring every subsequent year to keep feeding and improving the soil. Remember the thicker the mulch, the more weeds you’ll supress and the more you’ll improve your soil, don’t be stingy.

Use a Devon shovel or your hands to spread out the mulch and use a rake to gently ensure you have an even layer.

Types of Mulch

Leaf Mould – Easy to make (see last months article about Gardening on Clay). Low in nutrients but a fabulous soil conditioner that will help introduce and encourage the mycorrhizal fungi in your soil. Improves aeration, drainage and the production of humus.

Well-Rotted Horse Manure – retains moisture and is higher in nutrients. It should not smell of anything other than compost. If it does, it is not ready to use and needs more time to break down. Ideal if you are using it to mulch around roses or other hungry plants and fast-growing veg. Usually takes up to two years to break down to a point at which it safe to use. Using it earlier than this could mean that there is a high amount of Ammonia still present, and this can damage roots and scorch plants. It will also remove nutrients from the soil as it breaks down. DO NOT use farmyard manure unless the farm is guaranteed to be organic, as it could contain large amounts of hormones, which are routinely fed to animals bred for meat, to make them grow faster and larger. These hormones do not break down in the soil and will eventually leach into the environment and could cause long term damage to our wildlife.

Composted wood chips – the smaller the wood chips the better as the smaller particles will hold moisture and break down more easily. Ornamental bark is not a good mulch for an area in which you plan to plant. It should be noted that as the wood breaks down it will use up the available Nitrogen in the soil so you may need to compensate for this while the process is taking place. The addition of green cut material like weed free grass clippings mixed in can help offset this. The Nitrogen leaching will slow once the bark chippings are fully rotted down.

Garden Compost – is a good all-round mulch and there are various methods for making it.

‘Quick cook’ compost is made without the interaction of worms and is broken down quickly due to the microbes within the heap. It also produces a larger amount of heat so is not suitable for making on top of bare earth. However, it kills all weeds and their seeds as well as viruses and is relatively fast to produce. This link will take you to a step by step recipe written by Ray Broughton. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.beechvillage.org.uk/site/wp-content/uploads/2014/04/The_quick_cook_method_of_compost_making.pdf

‘Slow cook’ or the normal type of compost made by gardeners, consists of piled up grass cuttings, spent flowers, leaves, vegetable peelings, paper and cardboard and requires an even mix of carbon and nitrogen i.e. dried brown vegetable matter and fresh green vegetable matter. This takes longer to make and is often helped along by the presence of worms in the heap. It will not kill perennial weeds, seeds or viruses so be careful what you add to the pile. A few weed seedlings are easy enough to deal with but bindweed, mares-tail or ground elder is another matter.

Spent Mushroom Compost is usually alkaline so should not be used around lime hating plants like Heather, Rhododendron, Azalea and Camellia but is great added onto vegetable beds particularly for brassicas and potatoes. Finding the occasional edible mushroom is an added bonus.