Cultivating vegetables organically and sustainably begins with a respect for, and the maintenance of, soil. A healthy, living soil is the foundation of a successful garden. Efforts to control weeds, pests, and irrigate may be rendered ineffectual without it. The quality of a soil is usually determined by examining its fertility and texture. Fertility is an assessment of an intricate combination of essential nutrients, proper pH and the presence a diverse array of symbiotic fungi and microorganisms. In regards to nutrients, three primary elements that plants require are nitrogen, phosphorous and potassium. (In general terms, nitrogen for the healthy growth of leaf and stem, phosphorous for root growth and potassium for overall growth and health.) Trace minerals, such as calcium, magnesium, molybdenum and zinc are also required for proper health. The second principle component, texture, is made up of particle content (ratio of sand, silt and clay), the size of the particles and how cohesive they are, or friability and tilth. A proper balance of sand, silt and clay allows for adequate circulation of air and water. With all this in place, roots can grow and provide tremendous support and lift, or tilth to the soil.
Cultivation by definition is human intervention in the natural growth of plants with the intention to improve and reap benefits from that improvement. One way of of initiating this improvement whilst maintaining diversity and encouraging the health of the soil is double digging. Double digging is different from the traditional way of digging over the ground in that, as the name suggests, you dig twice as deeply as normal. In traditional vegetable growing you normally dig to about a spades depth and turn over the soil. In Double digging you will be digging over the ground to a depth of about two spades deep. Although it is labor intensive, it is a means of providing lasting improvement to a garden.
Some advantages of double digging include:
- Much higher yields for the same amount of space
- Soil is aerated and allows better moisture retention
- Higher earthworm activity
- The soil is very loose and makes adding Organic matter much simpler
- Helps to find and eliminate deep rooting woods for a clearer bed
Once you have Double Dug a plot the soil will be so loose to such a great depth that you will be able to just quickly fork it over each year in a few minutes. There are many online resources going into great detail on how to double dig , but there are a few simple guidelines to follow:
1. Mark out the area you wish to use
2. Dig it one Spade deep and throw the soil to the side
3. Start at one end using a fork and dig over the trench a forks depth deep, turning it, breaking up the soil and evening out as you go
4. DO NOT stand on ANYTHING you have forked over (more on this later)
5. Hop out of the trench
6. Add a good layer of Compost or Organic matter to the trench
7. Fill in the trench with approx one spade of good organic material to every three spades of the soil you have dug out
8. Job done!