The use of deep beds as a method of growing crops has become very popular with organic gardeners for several reasons, including:
The basic idea of the deep bed is that you divide your plot into sections about 2-3m (6-10) long by about 40cm (4) wide, separated by pathways about 500cm (2) wide. The dimensions are important: the width should be no more than is comfortable to reach across (for weeding, planting, harvesting and the like) from either pathway. The length should be long enough to be usable, but not so long that you are tempted to take a shortcut across the middle. If you do find yourself doing this, cut the bed in half with another path. When planning the layout of the deep beds, try to align them so that the length of the beds is on a north-south axis, to give the crops maximum benefit from the sunshine, and when planning the cropping of the beds remember to site the tall crops on the northern side so that they do not overshadow the lower growing crops.
Many people use wooden or plastic supporting walls around the beds. You can make a frame out of planks of wood, if you wish. However, if you have any trouble with slugs or snails (and who doesnt?), you will quickly find that these provide a lovely little haven for them. You may prefer to go without, or you may work on the principal that, if you know where the culprits are, they are easier to deal with.
Although it may be tempting, to make the layout look attractive, dont stagger the paths. Put them in straight lines wherever possible. Remember, you will probably be wheeling a barrow down them at some point, and a straight line is the shortest route between two points.
If youre doing a four-course rotation, double dig one bed in four for four years, incorporating large quantities of compost and, if possible, farmyard manure, as you replace the soil, and removing all the perennial weeds. The incorporation of large amounts of organic material means that the completed bed has a surface several inches higher than the pathway on either side. These heavily manured beds will be used for the more hungry crops, such as brassicas. Single dig and weed the remainder. From this point on, the beds arent walked on or disturbed.
The initial manuring of the beds will provide adequate nutrients for the first years cropping. From then on an annual dressing of blood, fish and bone or another organic fertiliser in the Spring, together with further applications of compost as a mulch, will keep soil fertility high.
Check the pH of the beds every other year with a soil testing kit and apply a sprinkling of calcified seaweed if the beds are becoming too acid. Avoid any major disturbance of the soil: just sprinkle the fertiliser or calcified seaweed onto the surface and hoe it in lightly. Because the soil is so friable, it is possible to harvest deep-rooting crops such as carrots, parsnips, salsify and scorzonera without the aid of a fork: they can simply be pulled out by hand.