Page 15 - ALG Issue 3 2018

#NODIG
Principles and why it works
Soil structure the natural way
Most soil already has a good structure for plant roots to grow, and is full of growth-promoting organisms. However, they do not work so well after being disturbed.
Millions of fungal threads, nematodes and earthworms, to name a few, are being helpful right under our feet, mostly out of sight. We need to help them to help us.
Advantages of no dig
1. Weeds germinate less, because their seeds are not exposed
to light during cultivation, and because organic matter on the surface (instead of dug in) is a weed suppressing mulch, both physically and through encouragement of fungi near the surface.
2. Mycorrhizal fungi stay intact, then help plant roots to find more nutrients and extract more moisture, because they are smaller than roots and can reach into tiny crevices.
3. You have access in wet weather because drainage is good: the soil’s structure has not been broken by tools or machinery, water runs away and you can garden when you need to. Mud does not stick to your boots!
4. You can quickly resow or replant at any time of year, with no soil preparation needed. Simply twist out plants when you clear a preceding crop to leave most roots in the soil, and remove any surface debris.
5. Moisture is retained and is available to considerable depth, because there is no ‘shatter zone’ caused by cultivations.
6. Warmth is retained by soil in winter because deep-level warmth can rise, unhindered by damage from cultivations: my gardens have always been admired for their early harvests.
Comparative trials
For 11 years I have been recording harvests in dig and no dig beds, surface area 7.5 square metres each. Total harvests in this time are 863.95kg dig, and 923.42kg no dig. In nine years out of eleven, the no dig was higher yielding. My website has details of this trial, under the Learn banner.
Mostly there is not a huge difference in growth, but one of the most common variations is stronger growth in early spring on no dig. In a cold spring such as 2018 this was especially marked, that seedlings preferred starting life in surface compost, compared to sticky soil in which the compost was incorporated while digging.
Also this spring there was more slug and wireworm damage on the dig bed, which contradicts the common assertion that digging allows birds to eat pests. What should also be mentioned is that digging allows birds to eat worms, and disrupts the natural balance of pest and predator, for example beetles that eat slugs. I wish there was more research on this because, from what I can find, there needs to be more understanding about how soil organisms all interact.
No dig on clay
At Lower Farm, Somerset in 1999/2000, I took over a third acre of clay soil which had been compacted in wet weather by heavy machines. There were putrefying lumps of grey and airless soil, whose surface was sticky in winter and rock-hard in summer. Gradually my mulches changed it to brown, healthy clay as soil life multiplied and created a structure, without any cultivations.
I cleared the
weeds by hand and
surface mulched
with 3-5cm compost
which was 18 month
old horse manure.
In the first year, crops
were below average as
the soil was recovering.
But in the second year there
was good growth; for example, parsnips grew deep and long into the still dense, but more aerated clay.
Every autumn I spread another 3-4cm compost and from year three onwards my vegetables were abundant. Furthermore weeds were few and easy to pull or hoe, in a surface which stayed soft in dry weather and was not sticky in winter.
My conclusion is that feeding earthworms and other soil organisms from above allows soil to recover damaged structure over time: https://www.charlesdowding.co.uk/courses/homeacres- courses/e.
A rare exception is soil where a true pan has developed, such that growth and drainage are awful. In this case a dig or forking is worthwhile, just once.
Incidentally, what is sometimes referred to as “compaction” is just soil’s natural firmness, which is good!
Virtues of compost
Compost holds nutrients in water-insoluble form. Therefore, you can spread compost even in autumn, after which it is washed through by rain before plant roots have access to it.
Nutrients are then made available by the combination of:
• Air and soil temperatures high enough for plant
photosynthesis/metabolism, which causes roots to signal
fungi with requests for food, and moisture too.
• Fungi in compost and soil, mainly mycorrhizae, which are
able to find nutrients for roots.
Chemical fertilisers are a more chancy way to feed plants because
they are water soluble, damage soil fungi and they may be leached out by rain, before plants can use them all.
Compost is the best mulch in our damp UK climate, because it does not offer habitat to slugs.
Avoid mulching with straw or hay. Paths can have mulches of half- decomposed and small pieces of wood, but always be careful not to increase slug habitat.
Charles Dowding
Charles Dowding runs day and weekend courses at his garden in Alhampton, Somerset, one mile from Castle Cary railway station. Details are on his website https://www.charlesdowding.co.uk/ courses/homeacres-courses/
General
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