In this edition of The Overstory, special guest author Michael Pease, Coordinator of the European and Mediterranean Vetiver Network, describes the uses of vegetative erosion barriers, highlighting their use in agroforestry.

Vegetative Erosion Barriers

The problems of retaining soil, water and plant nutrients where they can support timber growth and fruit production are critical to productive agroforestry. Yet we are steadily losing our soil resource and much of our water and plant nutrients is lost in run-off.

Previously, solutions to problems of soil erosion and to soil and water run-off have been sought mainly from earthworks and engineered constructions. However, such structures often prove to be costly, ineffective, and unsustainable. The solution lies in permanent, vegetative barriers planted on the contour. There is an upright, tufted, deep-rooted and very dense grass that is proving to be one of the prime tools in providing a solution to these problems, particularly in tropical countries. It is called Vetiveria zizanioides or vetiver grass.

Editor's Note

This issue of The Overstory departs from the usual format. Instead of presenting a specific technique or practice, it introduces a context, a way of thinking about farming, a paradigm.

This context is the integrated approach to farm systems.

The Integrated Approach to Farm Systems

The integrated approach comes from the perspective that whatever we are growing now, it was originally part of an ecosystem, its native environment, where for thousands of years it interacted with many kinds of other living things, from soil organisms to animals, insects, and plants. It was "plugged in" to natural processes, and grew without any human help. The integrated approach is about recreating and integrating into the farm some of the beneficial connections and natural processes that support productivity.

Editor's Note

Dear fellow agroforesters, Whether you grow your own trees for your project or purchase them, you are probably aware that the quality of the seedlings is important to the success of the project. But what is a "good quality seedling?" How do you know if the seedlings you grow or purchase are high quality? This Overstory excerpts the original article authored by forestry advisor Norman Jones, and published by the World Bank (ASTAG), and offers advice on the essentials of good planting stock.

Essentials of Good Planting Stock

The extent of the world land base that is being reforested or afforested is significant and is growing still. Unfortunately, several of these efforts are wasted in planting poor quality trees. While some problems are beyond the forester's control--inclement weather, insect attacks, disease outbreaks, animal browse, and the like--others fall within the forester's influence. Two such areas are seed collection, and planting stock preparation and selection. Measures outlined in this bulletin provide basic guidelines that will help the forester ensure a cost-effective means of producing high quality seedlings.

Improved Fallow and Land Rehabilitation

Given enough time, natural processes will restore productivity to degraded or damaged land. Traditionally, farmers have used the practice of "fallow" to allow crop land to rest without crops and be rejuvenated naturally. When the fallow is enriched with fast-growing trees, shrubs or vines, the practice is called "improved fallow." Improved fallow is an agroforestry practice that has its origins in slash-and-burn agriculture. Farmers use improved fallow to accelerate the process of rehabilitation and thereby shorten the length of their fallow periods. The technology can be applied to any agricultural land that is not under cultivation in order to accelerate recovery, increase nutrient reserves, and improve the potential for future productivity on the site.

To create an improved fallow system, farmers scatter seeds or plant seedlings of fast-growing plants after harvest of the crops from the site. Normally, nitrogen-fixing plants are used, because they are vigorous, deep-rooted, tolerant of drought, and have the ability to accumulate atmospheric nitrogen (see Overstory #4 on Nitrogen Fixing Trees ). The trees and shrubs are left to occupy the site for several months or years. During the fallow period, the plants accumulate nitrogen from the air and from deep layers of the soil, and drop their leaf litter to enrich the soil and conserve moisture. When the trees are removed at the end of the fallow period, their roots remain in the soil to decompose gradually, releasing additional nutrients to the subsequent crops.

"Farm animals" to most Westerners usually means pigs, cows, goats, and sheep. Indeed, these same animals have been heavily emphasized by development projects. However, in many parts of the world, the major protein sources are not from these animals, but instead from "microlivestock"—small animals managed for food. There are over a thousand kinds of reptiles, rodents, insects, birds, and other small animals that can be categorized as microlivestock. Some of these, like the guinea pig, are highly domesticated and raised in close quarters with people. Others are only semi-domesticated, and live out on the farm or forest, like iguanas. Some microlivestock are currently collected from wild areas, with domestication projects underway, like the giant forest rats of Africa. Microlivestock have been essential to human nutrition for thousands of years. In the future, these small animals may be major players in food security, environmental conservation, and economic diversity.

Honey Bees and Agroforestry

All fruit and seed crops need to be pollinated in order to be productive. Honey bees are very active and effective pollinators for many kinds of crops, the integration of honey bees into agroforestry systems can improve crop yield dramatically. Properly managed pollination by honey bees results in larger, well-formed fruits, berries, vegetables, nuts, and seeds. At the same time, the honey bees produce honey and a wide range of other products that are potential sources of income.

While managed pollination by honey bees has become standard for large-scale agriculture in temperate areas, innovative beekeeping practices are springing up throughout the tropics. The subject has wide appeal to tropical farmers because beekeeping does not require large amounts of labor, land, or capital, but enhances productivity and contributes to sustainability of farming systems. Beekeeping can be practiced successfully on a part-time basis, and yields a wide array of high-value products that can increase a farmer's income by 40-60%.

Beekeeping is being practiced in tropical orchards, home gardens, plantations, and many agroforestry systems including coconut, coffee, pineapple, and others. Beekeeping is also a relatively low-impact activity that can increase local people's income from native forest or conservation areas.