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May 2007: Publications

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Bed Widths
By Tom Marino

Returning and preserving more area to the wilderness; feeding more people from a limited space; creating thick and thriving mini-ecosystems: these are some of the many reasons to grow as much food and calories as possible in the smallest area. One strategy to help get you there is to increase the amount of cultivated area and/or decrease the amount of path area.  John Jeavons commonly recommends 6-ft-wide bed connected to 15-in-wide paths, allowing approximately 79% of one's growing area to be cultivated (the back legs of a wheelbarrow are around 15'' apart).  The general response to this suggestion, however, is: "How do you reach and maintain the center of that bed without falling into it?"  Assuming 2 ft is as far as most people can reach into a bed from a narrow path (without dropping a hand, knee or foot into the bed for support, 4 ft would appear to be the maximum manageable bed width.  By stretching this bed to 6 ft, as John suggests, a 2-ft-wide gap or strip would emerge from the center.  So what could be done with this space?  One possibility is to plant it full of alfalfa.  But why?

Low Maintenance: Alfalfa is a perennial that has been known to survive for over 25 years (you may want to remove the alfalfa before this to prevent mineral deficiencies in the soil).   Compost and amendments can be added to the inner area right after the winter crops in the outer area have been harvested with the help of a digging board placed on the outer 2 ft of the bed. As long as the outer crops are fairly short, the alfalfa can be repeatedly harvested standing from the path (using a pair of long-handled pruning shears).

Compatible root system: Alfalfa possesses long, straight taproots, which shouldn't compete too much with adjacent crops for nutrients.  This vertical root system will also be safe from disruption when the outer sections of the bed are being single- or double-dug.

High yields: Alfalfa can produce 69 lb of air-dry biomass per year (intermediate yields according to HTGMV).  In a sustainable, closed-system farm, food is grown to feed the people, and carbon (i.e. biomass) is grown to feed the soil (via root mass and compost).  Alfalfa's ability to produce large amounts of carbonaceous biomass in a small area takes the pressure off of other beds to produce biomass.  Thus, more area is open/available to grow potatoes and other special root crops, which tend to yield the largest amounts of calories per unit of area, but not much compostable biomass.

Nutrient provider: Alfalfa's deep root system absorbs and stores hard-to-reach nutrients (nitrogen, calcium and other trace minerals) that would otherwise remain in the ground.  These nutrients are made available to other crops as its leaves and stems are harvested, added to a compost pile, and returned to the soil in the form of cured compost.  Also, alfalfa is a legume, attracting and encouraging nitrogen-fixing bacteria.  If the cuttings are timed so that the alfalfa does not go to seed, nitrates will continuously accumulate in the soil, benefiting alfalfa's neighboring crops.

So far this is just an idea because we haven't yet started digging those 6-ft-wide “alfalfa sandwich” beds and thus don't know how practical or beneficial this strategy is. Although it won't be preferable to squeeze a wheelbarrow down a 15-inch-wide path or harvest alfalfa from 2 to 3 ft away, you will be increasing the amount of beds, crops and life that make up your garden.  Just how large of an increase? A mini-farm layout of 6-ft- wide beds and 15'-in-wide paths contains approximately 16% more bed area than a layout with 4-ft-wide beds and 2-ft-wide paths (i.e. 16% more food, more calories, more biomass, etc. This could be an attractive design for both urban areas, where land is far from cheap and boundless, and larger horticultural operations, where substantial returns can result from small improvements in land use.




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