No-dig organic vegetable gardening
As the name suggests, no-dig gardening is an organic method of growing vegetables without manually turning over the soil between crops. This may sound somewhat unconventional but it is actually how nature works – as vegetation dies, it falls to the ground where it decomposes and is combined with the soil by the earthworms and other organisms. The earthworms in the soil improve the drainage and soil structure through their burrowing activities and their crumbly, aerated casts. Other organisms in the soil further breakdown the organic matter the worms have dragged down, releasing food for growing plants and forming humus.
Even with no-dig, some soil disturbance is inevitable when sowing, planting and harvesting, but this is a lot less than the conventional digging between crops. In the longer term, conventional digging is generally detrimental to the structure of the soil and results in increased losses of soil moisture and organic matter.
The main advantages of no-dig gardening are:
- The beneficial organisms within the soil will flourish in the undisturbed soil and, over time, will improve the soil structure.
- The soil and the balance of nutrients are more easily maintained.
- Losses of moisture and organic matter will be greatly reduced.
- Fewer weeds due to the surface mulch of organic matter and the lack of bare soil.
- Higher crop yields possible in some areas.
- The lower temperature under an organic mulch can be an advantage, especially in summer when soil temperatures can be excessive.
- The seasonal effort of labour-intensive digging will no longer be required.
The main disadvantages of no-dig gardening are:
- It may take longer to improve a poor soil.
- Pests within the soil are not exposed to predators.
- Soil can become compacted or poorly drained if it is not property managed.
- Soil temperature under an organic mulch can be several degrees lower than bare soil, which can delay the development of crops.
Combining the best features of ‘digging’ with ‘no-dig’ is often the best approach. The soil may need initial cultivation to improve the soil before starting to use the no-dig approach and the soil can still be turned over occasionally, such as when incorporating green manures.
Approaching no-dig gardening
To get the best results from no-dig gardening, the soil should be in a reasonable condition structurally to start with. This may involve digging to improve drainage and remove any compaction.
The no-dig technique is particularly successful when used with a bed system, where the beds are small enough that they can be worked on without having to walk on them – thus reducing the chances of soil compaction. Using raised beds has an added attraction that relatively small quantities of ‘good soil’ can be imported to make the beds above the natural soil level which may be of questionable quality.
Preparing the soil
Ahead of sowing or planting vegetables, an organic mulch is spread evenly over the soil, or it can be applied just around planting positions for widely spaced crops. The earthworms and soil organisms then start to breakdown the mulch thus feeding and improving the soil structure.
Sowing and planting
Most crops are grown in the same way as they would be on a conventionally dug bed – annual crop rotation between beds should also be applied. Before sowing or planting, the layer of mulch is first scraped back to expose the soil. Once a no-dig system has become established, the surface soil will be fine and crumbly - ideal for direct seed sowing. Seedlings are planted into holes in the soil made with a trowel. After sowing/planting, the mulch is spread back as the plants begin to grow; this helps suppress weeds and also continues to 'feed' the worms and soil organisms.
Weeds and weeding
The numbers of weeds encountered on a no-dig bed are normally a great deal less than a conventional dug bed as dormant weed seeds are not brought to the surface. The organic mulch will further reduce the quantity of weeds and help retain soil moisture.
Light hoeing to remove annual weeds when the soil is exposed before they set their seeds will gradually deplete the reserve of seeds in the bed.
Any perennial weeds should be loosened with a small fork around the roots and lifted out, disturbing the soil as little as possible.
It may be possible to simply pull up root crops out of the ground. Alternatively a fork can be used to loosen the soil around them causing minimal disruption to the soil.