Looking After Your Soil / No-Dig Gardening
Healthy soil is a living ecosystem. When we dig the soil we disrupt that ecosystem, disturbing worms, microscopic bacteria and other organisms. This includes mycorrhizal fungi which bond with plants and help them to access nutrients and water through association with the plants' roots. Digging also causes the release of carbon, oxidizing it to form carbon dioxide which is released into the air, contributing to global warming and climate change.
By keeping this ecosystem intact we can have healthier soil, healthier and more productive ornamental plants and crops, and make is easier for ourselves in the process.
The key to the no-dig approach is to add a layer of organic matter mulch (well-rotted animal or plant waste) which replicates what happens in nature when leaves, plant matter, and animals are left to degrade on the ground. The benefits of this are:
- Less weeding. The layer of mulch smothers and weakens any weeds and most weeds that do grow in it can be pulled out easily.
- Less digging. The worms and micro-organisms feed on the organic matter and will mix it with the underlying soil, releasing nutrients in the process.
- Less watering. If laid when the underlying soil is moist, there is less evaporation and so the water is kept available for the plants.
- Better absorption of water after heavy rain, reducing damaging water run-off.
- Conserves soil carbon
- Less erosion of soil by wind and rain.
- Builds up the ecosystem underground to help keep your plants healthy
For existing beds that already contain plants already just add a layer of organic matter any time from late autumn to early spring. Make the layer 10cm deep if you can but don't mound it up around plant stems. The soil must be moist when you apply it or it can be difficult to re-wet the underlying soil especially if you are doing it quite late in spring.
If you have empty beds such as veg beds, and you know there is a problem with aggressive weeds you could add a layer of cardboard under the mulch which prevents any seeds germinating but still allows rain to penetrate the soil. Never use sheet plastic as this is impermeable to moisture. Some people use permeable landscape fabric on the top of the mulch but I prefer to keep my plastic use to a minimum. If adding cardboard you should do it in autumn/winter to allow time for the cardboard to break down before spring. By spring when you are ready to plant, if the layer has not incorporated naturally, you can incorporate it into the underlying soil as you plant.
How to create a new planting bed for veg and salads crops
If there are lots of weeds, remove the tall growth and cover with untreated cardboard. (Do not use plastic as this does not degrade, nor carpet which contains chemicals.) You can also lay the cardboard directly on existing grass.
Add a 15-20cm layer of organic matter. This can be well-rotted plant material, leaves, straw or grass mowings, or a mixture of any/all of them. Tread it down.
Wait 6 months for the weeds to die down and the soil organisms to have worked on it. (Could take a year for tough weeds.)
If you are starting from bare ground with no weeds, just add a 15cm of organic matter (well-rotted plant or animal waste). No-dig experts say that you can plant straight into this, although I have not tried it myself and am concerned that some plants may rot in it.
Don’t worry if it looks a bit high, the organic matter will sink over time.
Top this up with a new layer of organic matter each year in late winter or spring.
How to create a new planting bed for ornamental plants
If the soil is workable you can plant and then add the organic matter as a mulch. If the soil is very heavy, or compacted, or is very light and sandy, it is worth digging over the soil and then forking in organic matter first. I know this means disturbing the soil to start with, but it can help to break up heavy clay and increase the water and nutrient holding capacity of the soil so is a bit of a trade-off. Once planted, the soil can be mulched with composted plant waste, ensuring that it is not mounded up around the plant stems. The soil can then be mulched with a 5cm layer each year in late winter or spring. No further digging should be done as the worms and microorganisms will work to continually incorporate the compost into the soil.