Hedgerow farming. In alley cropping, a form of agroforestry, farmers plant rows of trees close together, leaving 5 to 10 times the hedgerow width between the rows for crops or pasture.
Ames, Iowa — RAYMOND ROWE works out of an office in Washington, just a short stroll from the Potomac. But the Welsh-born, one-time rugby star and agroforestry expert with the World Bank wears a tan he has picked up in a dozen far-flung regions of the globe. For something like one-third of each year he's in places like Indonesia, Malaysia, several West African states, and some in Latin America - wherever tropical forests are falling in the face of exploding populations.
He's not there to stop the felling but to promote a compromise, something that offers hope to people who face a quite desperate future as soil fertility disappears with the dwindling trees. He calls the compromise alley cropping. It's a land-use system that promises to break the farm-today, abandon-tomorrow cycle common to these regions.
Mr. Rowe is quick to stress the difference between forest destruction taking place in some parts of the Western Hemisphere to produce cheap beef for the American hamburger market, and tree cutting in regions where he is working. ``I'm not talking about optional clearing, but inevitable clearing,'' he says, ``regions where trees are disappearing because people are running out of places to live.'' Indonesia is the prime example, but there are many others.
Clearing the forest is only a temporary solution to the need for land. Within five years the fertility is gone and the exhausted soils are abandoned in favor of yet more clearing. Tropical soils are fragile at best and erosion becomes widespread. Even in regions of moderate rainfall, the desert's advance becomes inevitable.
In Indonesia, erosion is less threatening, but the result is only marginally better. Abandoned land in that crowded nation is overtaken by a grass that prevents natural reforestation and creates a fire-prone environment. And while it has some use as a thatching material, it is unpalatable to grazing animals. In effect, a desert of sand is replaced by a desert of grass.
Worldwide the situation is critical, because 11 million hectares (27 million acres) of tropical forest disappear every year. That's the equivalent of converting Minnesota into a treeless plain in less than two years.
Increasingly, agroforestry is being seen as a practical and ecologically acceptable answer to the problem. Alley cropping is a specialized form of agroforestry.
It involves planting two to four rows of leguminous (nitrogen-fixing) trees on two-foot centers, so they become a hedge leaving 5 to 10 times the hedgerow width for crops or pasture, then more trees and so on, until the area to be farmed is covered in this way.
The result is a series of oblong fields or alleys, protected on each side by the hedgerows. On sloping ground, the trees can be planted on the sides of the terraces, leaving the flat area in between for cultivation. A variation on the theme is to create a series of hedgerow-protected squares.
Stabilize the fragile soils, arresting both wind and water erosion.
Fix air-borne nitrogen in the soil, because they are legumes and draw up nutrients too deep for the shallower-rooted crops.
Fertilize and add much-needed organic matter to the soil when the clippings are spread on the cultivated alleys. Alternatively, the clippings become fodder for livestock and the manure is spread on the soil.
Provide a refuge for birds, which control insect pests.
Yield flexible canes that can be woven into baskets or other containers or used as fuel.
Not every tree is suitable for alley culture. ``We want leguminous trees that fix nitrogen, that send roots deep into the soil rather than spreading them sidewards where they interfere with the crops, and they must coppice well,'' says Rowe. By coppice, Rowe means that a tree must be able to regenerate from the remaining stump when it is cut down.
Such a tree is leucaena, found in the moist tropics. Another is gliricidia. In more arid regions, various species of the thorny acacia are likely to prove more appropriate, Rowe says. The World Bank forester sees modified forms of alley culture fitting into the sustainable agriculture picture of the West as well. ``In the United States, black locust and possibly alder'' would be appropriate species, he says.
A principle of alley culture is to maintain the trees as a hedge. ``You must never let a tree get away from you,'' Rowe stresses. ``What you want is a hedge about chest high. You're after leaf production for fertilizer or fodder rather than wood.'' Too high a hedge also starts shading crops, which is not wanted.
Alley culture in one form or another has been practiced for millennia in various parts of the world. Michael Benge of the US Agency for International Development says that the Aztecs and Central American civilizations ``are thought to have used similar systems'' to sustain maize yields and control erosion on the steeply sloping lands they farmed. The Dutch did some work with alley cropping during the early colonial period in Indonesia, and Dr. Benge worked with the system among the Montagnards of Vietnam until temporary imprisonment by the North Vietnamese brought an abrupt halt to his work.
In the early 1970s, alley cropping caught the attention of agronomists on a wider scale, and the World Bank and other international organizations began funding research projects in several parts of the world.
Writing about work by the International Institute for Tropical Agriculture in Ibadan, Nigeria, Benge says that luceana ``grown in an alley-cropping system, cut and added to the soil as a green fertilizer, tripled maize yields by the fifth year, compared to the control where nothing was added to the soil.''
More recently the system has been introduced into Haiti in the hopes that it will arrest erosion and restore some fertility to the devastated hillsides of that nation.
D.K. Nair, in charge of the agroforestry program at Florida State University, returned from a recent inspection trip declaring the Haitian experiment a ``success story.'' What excited Dr. Nair, a longtime research scientist with the International Council for Research in Agroforestry in Nairobi, was the fact that ``farmers accept the philosophy'' behind the concept. To break the initial inertia of the farmer in these situations is always hard, Nair points out, ``because they have too much to lose if the concept fails. But they are seeing how effectively it is saving the soil.''
For his part, Rowe tempers his enthusiasm. ``We can't say this is it, at least not yet. But the indications so far are that a farmer can get at least 15 to 20 years of crops off alley-farming land without needing any outside inputs.'' That's not to say, he adds, that alley cropping won't ultimately prove ``totally self-sustaining.''