Roots on the Rooftop. Shallow-bed gardening techniques may help to feed the world's hungry

In North Fort Myers, Fla., Dr. Martin L. Price is growing kohlrabi which he sells to a local store. That on its own is of no great significance, until one realizes he is growing the vegetable in a four-inch layer of old wood chips spread over a slab of concrete. On the roof covering some nearby rabbit cages, a variety of other vegetables are growing, this time in a thin layer of wood chips and ground corncobs. Elsewhere hundreds of square feet of these ``shallow bed'' gardens have been laid out on plastic sheeting, several of them producing excellent stands of garden peas in three-inch beds of grass clippings. The purpose of these and a host of other experiments being overseen by Dr. Price is to make it easier for the world, principally the third world, to feed itself.

Dr. Price is executive director of Echo Inc. (Educational Concern for Hunger Organization), a technical support group that aids church and other organizations that work on behalf of the world's hungry. The work includes trials in conventional garden beds as well as shallow beds suited to rooftops or other soil-short situations.

Working in this manner Echo has been able to influence food production in minor and sometimes major ways in over 50 different countries. Echo personnel, however, have found that new growing techniques are not readily accepted in the third world if they have not first been tried in an agriculturally successful part of the world, hence the shallow-bed culture currently under way at the Echo farm in Florida.

It was the flat concrete rooftop of the Grace Mountain Mission's orphanage in Haiti, typical of many rooftops in tropical areas, that initially inspired the shallow-bed concept. In Dr. Price's eyes it represented 2,500 square feet of prime ``arable'' land, enough for the orphanage to grow all its own fresh produce. How many other sunlit rooftops, he wondered, could be turned into productive mini-farms?

Soil would prove too heavy for most rooftops, so Echo began looking into other growing mediums. Because of a plentiful supply in the group's region, wood chips have been most frequently used. Lawn clippings and ground corncobs have also proved outstanding.

Other possibilities would include sugar cane bagasse, rice hulls, straw, and peat moss. The idea, of course, is to use whatever materials are most readily available and inexpensive.

Initial experiments included beds that were three feet deep and others that were a mere three inches in depth. To everyone's surprise, the shallow beds produced markedly better crops than the deeper beds. Ever since experiments have involved shallow-bed culture exclusively, with somewhat deeper beds used only when root crops such as carrots are being grown.

Because the aim is to produce a system that will work in the most underprivileged parts of the third world, the most sophisticated piece of equipment used is the watering can. Plant nutrients are watered in every other day. Straight water is applied on the intervening days.

In the first year all nutrients are provided by hydroponic fertilizers or else manure teas, but in subsequent seasons the decaying wood chips provide many of the nutrients. While wood chips work best once they are partly decayed, grass clippings are a most effective medium within a few weeks.

``We now prefer grass clippings to wood chips,'' says Dr. Price. ``Fresh grass is placed in piles and allowed to heat up. After about a month the grass is placed on plastic sheets [to simulate a roof top], wet down, and trampled into a rather unappealing mat. Fertilizer is added as though it were bare, poor soil.

``We have been able to plant even small seeds like radishes directly into the clippings if we keep the surface consistently damp until the seeds have germinated. Excellent vegetables are growing in a layer of grass that has now matted down to only an inch or two thick.'' After a full season the grass breaks down, according to Dr. Price, ``into a rich, black organic soil.''

Apart from rooftops, other options for shallow-bed gardens in the United States include paved yards, unused parking lots, and, to a limited degree, on top of soil filled with tree roots. Tree roots need oxygen, however, so too great a shallow-bed covering would damage the trees.

Dr. Price has found that the shallow beds do not use more water than the deeper ones, but they do need watering every single day. The homeowner using the system could not leave for a week of vacation without hiring a ``garden sitter'' to attend to this daily chore.

Echo Inc. (RFD 2, Box 852, North Fort Meyers, Fla. 33903) is a nonprofit organization whose Echo Development Notes dealing with new growing techniques and underutilized vegetables is sent free to groups helping small farmers overseas. In the US $1 a back issue is charged to help defray expenses.