No dig growing

Where to find the organic matter you need? Compost is becoming more available, and often cheaper, thanks to recycling of green waste, and there are surplus quantities of animal manure to be found in many localities, in addition to any compost you can make.

WHY

• No-Dig, with compost spread annually on the surface, makes soil more fertile, plants more healthy and helps reduce weed problems
• Fertility building from compost and manure on top is a copy of natural processes (forest floor, animal excretion on pastures) and works really well for vegetable growing.
• Worms and soil fauna are encouraged, then as they increase the soil becomes better aerated, without the disadvantages of digging (loss of moisture & tilth, extra weeds, expense of time and labour).
• In time, the soil surface, even on sticky clay, becomes darker and crumbly with a consistently good tilth of fine but stable soil crumbs.
• Throughout the soil, there is a proliferation of beneficial fungi, such as mycorrhizae, and bacteria. These help plant roots to find the nutrients they need, which may often be present already, but can remain unavailable to roots because of a lack of biological activity.
• Growth of plants in undisturbed soil with a mulch of compost is generally healthy and vigorous, and the healthy topsoil becomes easy to sow and plant into.    
• Time is saved, moisture is conserved, and weed growth diminishes - once perennial weeds are removed (by initial mulching or digging) and providing annual weeds are not allowed to spread their seeds.
• I run a dig / no dig experiment (see the archived monthly blog for December 2008 and January 2009) and find that vegetables often grow more strongly and more healthily on the un-dug beds. Total yields are similar but the quality of harvests is noticeably and intriguingly different.    This photo shows the four experimental beds, of which each pair are cropped the same.
• In summary, soil has it’s own life and structure, it benefits us to encourage and respect it.

 PHOTOS: top, drawing drills to sow carrots; bottom, my dig/no dig experiment, undug bed in front, then dug, then undug, then dug

HOW

• Remember that vegetables are hungry plants and require a soil that is well structured and full of life. First year dressings of organic matter may seem a lot but will repay the effort for years to come. Until the advent of chemical fertilisers, larger amounts of compost and manure were always used than has been the case since about World War Two. Since then, more emphasis has been placed on chemical nutrients, but they cannot provide soils with food for all its myriad of inhabitants who are so necessary in growing healthy plants.
• An initial dressing of 3-6" (7-15cm) of reasonably well rotted compost and animal manure, helps kill existing weeds and lifts soil fertility to a higher level for many years.
• One-off, six inch (15cm) dressings of compost in deep beds, well trodden down, are enough to kill existing grass and many perennial weeds such as buttercup, dandelion, and even small amounts of couch grass. Cardboard under the compost makes no difference as weeds are killed by the 6" of compost.             filling a new bed on grass, one half with cardboard
• Soil which has enduring perennials such as couch, bindweed and marestail will require a year of light-excluding mulch such as cardboard or black polythene, preferably above a dressing of organic matter, all sitting on top of the weed growth.
• In the absence of enduring perennials, vegetables can be sown and planted into compost-rich dressings as soon as they are spread. The combination of growing plants above and increasing soil life below starts an ongoing process of soil improvement. Even root vegetables such as carrots and parsnips will find their way down, unless the soil below was seriously compacted: in such a case, it may take up to two years for worms and other organisms to develop a good structure. An initial dig would speed this up if you are in a hurry. In my garden I have always grown extremely long parsnips on heavy clay, except in the year when I took on a new patch of compacted soil.    parsnips Gladiator, October 2009
• Sowing small seeds into clods of compost and manure is unlikely to succeed, so keep the finest, most crumbly organic matter for your surface layer. An excellent time to spread compost is in autumn, as soon as the previous crops finish. Then there is time for frost to break up any lumps and for worms to start taking it down, leaving a fair tilth by spring. It also helps, when the surface organic matter is lumpy, if you knock it around in February or March with a fork, just on the surface, to smooth out the lumpy bits. 
• Fine compost can be spread at any time of year, while lumpy compost or manure can  be used in the summer as a mulch around established plants such as courgettes, or between rows of growing vegetables, even parsnips.

When plants are harvested, remove all debris to the compost heap, tread down any lumps caused by pulling rooots out, and then for any harvests before the end of August you can sow or plant again, with vegetables such as autumn salads.

WEEDS and MAINTENANCE

After digging, soil recovers from the disruption by re-covering with weed growth. It also needs time to recover in a more general way*. By contrast when left uncultivated it grows less weeds - but there will always be some and they must be kept on top of. Vegetable growing is more bountiful and much easier in the absence of weeds! 

There are three different stages to pass through in reclaiming weedy soil for growing vegetables:

1. Initial composting and/or mulch of weedy and grassy plots, as described above
2. The first year of growing when some perennials may re-grow and need careful, frequent trowelling out. Also, when only small amounts of compost have been spread on the surface, there will be a flush of annual weeds for repeated hoeing.
3. Thereafter, fewer weeds still need regular weeding but it takes very little time. A weed is a weed however big it is - pull it when small and keep your plot clean! This approach means NO weeds going to seed, so you enter a virtuous circle of enjoyably clean soil, apart from weed seeds blowing in.

Clean, healthy soil, the promised land for all gardening, is also maintained by an annual application of at least one inch, preferably two of reasonably well rotted compost or animal manure. Soil kept healthy by a thin layer of organic matter on top will grow less weeds.

Keep the finest, crumbliest compost for applications close to sowing or planting time, also for slug sensitive plants such as lettuce and spinach, and for all sowings of small seeds (including carrots and parsnips).

 *Results from the dig/no dig experiment show bigger spring harvests on the undug beds, and bigger autumn ones on the dug beds.

Photo: a lettuce bed in May, after three pickings of outer leaves

PERMACULTURE

In case you are wondering, no dig is a ‘permacultural’ approach, using compost instead of more bulky mulches of unrotted organic matter, or mulches of growing plants. The latter approaches are not really suitable, as Patrick Whitefield says, for our “slug infested island”. 

For a comparison of dig and no dig, see the attachment in the Articles page of this site, Val Bourne's piece of December 2009