Weymouth, Mass. — ONE day last summer I came across a young woman hoeing vigorously in her family's kitchen garden. From the look of the garden, and the way she worked, two things were obvious: She had a talent for the work, and her energy was boundless. And yet she could have done a whole lot better. In this day of gardening enlightenment, I had to wonder why she still followed the old approach of planting in single rows with a heavily trampled path in between each row. A little change in garden design and she could easily have doubled the production while halving the effort involved.
Research in recent years has confirmed what French market gardeners knew last century and Chinese farmers have known for 4,000 years: Deeply dug beds, rich in soil humus, are several times as productive on a square-foot basis than the old row method; and the extra effort expended in the initial bed preparation is more than recouped in the season that follows.
Replacing rows with beds, 2 to 4 feet wide, immediately converts many of the old paths to growing space. But there is much more to it than merely putting unnecessary path space to more productive use. Deeply dug beds, which once prepared are never stepped on, allow oxygen and rainwater to penetrate deeply into the soil. Soil compaction, the bane of conventional farming and also of the row garden, is not a factor in the properly managed bed garden.
In these optimum conditions, roots can grow down instead of sideways in search of nutrients and moisture. As a result, plants can be spaced more closely. Once established, the leaf cover in these solidly planted beds shades out most competing weeds, saving on cultivating and weeding time. Soil temperatures are moderated and moisture conserved by the leaf cover, creating a beneficial growing environment for both plants and soil life.
If you plan to include raised beds in your garden for the first time, here are a few options:
1.Dig over the entire garden area to the full depth of the spading fork. Or rent a power tiller and till the garden as deep as the tines will go. If you have leaves, manure, or both to spread over the garden before tilling, so much the better. These will decay after being turned in, adding valuable humus to the soil.
2.Mark off where the paths will go, defining the beds. Make the paths at least 18 inches wide. Now, using a spade, dig out the paths by removing all the loose soil, piling it onto the adjacent bed as you go.
3.Rake smooth and shape, leaving a slight slope to the sides of a free-standing bed. If you plan to use wooden boards, landscaping lumber, concrete blocks, or some other material to support the raised beds, then there will be no need to slope the sides.
1.This involves loosening the soil to twice the depth of a spade or spading fork. Mark off the proposed bed and across one end dig a trench as deep and as wide as the spade. Take the soil removed from the trench and pile it alongside the far end of the bed.
2.Using your spading fork, push the tines deeply into the bottom of the trench and rock back and forth to loosen but not dig up the soil. Do this at 4- to 6-inch intervals across the trench.
3.Spread an inch-thick layer of compost or aged manure in the bottom of the trench.
4.Dig a second trench right alongside the first, throwing the soil on top of the organic matter in the first trench.
5.Keep repeating the process until you have dug across the entire bed. Use the soil you removed from the first trench to fill the last one.
6.Spread more fine compost, composted manure, or a balanced organic fertilizer on top of the now completed bed and rake it into the top few inches.
You will find that the addition of the organic matter and the loosening of the soil will have raised the bed several inches above the surrounding soil surface.
Note: If your soil, like mine, is on the sandy side, then do not loosen the subsoil at the bottom of the trenches. Research has shown this to be counterproductive, as it makes the bed overly well drained and vulnerable to drought.
The compost bed
This method is based on the German mound culture, but instead of an aboveground mound, the compostable materials are largely underground.
1.Mark off the bed and remove the top 6 inches of soil and put it to one side.
2.Dig down a further 18 inches to create a hole 2 feet deep. Place this subsoil in another pile away from the topsoil.
3.Place 6 inches of unshredded brush or woody prunings in the bottom of the hole. This brush traps oxygen for plant roots and soil microbes.
4.Cover the brush with a 6-inch layer of hay, leaves, weeds, or garden waste.
5.Fill up the rest of the hole with a mixture of subsoil and shredded organic matter, including manure if you have it. Otherwise, add a little nitrogen-rich organic fertilizer to the mix to stimulate the decay organism in the soil.
6.Finally, add the topsoil you first removed, enriching it with finished compost or aged manure if available. This final step raises the bed above the surrounding level.
As the organic material slowly decomposes in this compost bed it builds up soil quality, releases plant nutrients, and, initially, raises soil temperatures slightly, which in the spring can significantly speed up plant growth.
The beneficial effect of double digging and deep-bed composting lasts for years even in heavy soils, and in light loams it may never have to be repeated.