Friday, 28 March 2014

Deep Bed System - Why Dig?

Why Dig?
Artificial digger
      I used to think that bastard trenching was about burying someone you didn't like. College rectified this impression by pointing out that the term refers to a system of digging whereby the soil is turned over to a depth of two spade blades. Well-rotted organic material is incorporated into the bottom layer and the overall effect is that of aerating and enriching the soil as the series of trenches march across the plot, the soil from the next one filling its predecessor.

      All this seems very logical until someone asks the seemingly daft question 'but why dig at all?' Think about it: untold billions of acres of land have never been touched by a spade but are populated by a profusely growing collection of trees, shrubs, herbaceous plants and annuals. So why do we spend so much time breaking our backs under the impression that our way produces better results than nature? The answer to this conundrum lies in the simple fact that we walk on the soil, compacting the crumb structure and excluding air. Plants respire - a process which involves roots converting sugars into growth energy and one of the raw materials necessary for this to take place is the oxygen our size nines have squeezed out.
Natural digger
      One way round this problem is to adopt the deep bed system of growing: by creating a bed about four feet wide we present ourselves with an area we can reach across to cultivate plants without walking on it. An annual top dressing of a couple of inches of well-rotted organic material will then be incorporated into the soil by worms, mining bees and various other organisms. Their digging activities allow air to the lower levels, at the same time as incorporating a natural drainage system to cope with excess water. Creating a good crumb structure is what it is all about. Healthy soil crumbs will have spaces between, allowing water to drain and giving access to air. The crumbs themselves will contain a balance of organic material which acts as a sponge to retain enough water and nutrients for plants to thrive and the hard, impervious, mineral particles also do the drainage bit.

      By using a deep bed system we are working with nature, enabling natural soil inhabitants, of which there are millions per cubic foot, to beaver away at doing what they do best - breaking down organic material. Picture the scene: a leaf falls from the tree and a nearby worm, leaning on his mini Spear & Jackson stainless steel spade, wipes the sweat off his brow, grabs the stalk and starts dragging it into the cave he's just excavated. Easy, isn't it. Out with the deckchair.
Mining bee excavation between drive bricks
Mining bee
For more about worms go to composting - worms.

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