Practical experience is a key source of information on sustainable farming that can only be gained first-hand and can't be found in any book. The study of books is valuable too, but there is no substitute for seeing something in action. Many aspiring farmers feel awkward and don't know how to start to approach local old-timers, neighbors, or complete strangers whose work they have heard about or seen from a distance. Yet, it is an essential part of learning to meet other farmers in your region and get a first-hand look at their work, and hear about their experiences. These valuable relationships can be a wellspring of information, ideas, and inspiration for you, as well as result in long-term supportive friendships.

So, how does one go about approaching that person for the first time to ask to see their farm practices? To make it more comfortable, effective and enjoyable, there is a certain code of conduct that goes along with tapping into a farmer's wealth of information.

Natural forests are abundant systems–rich in diversity of species, stored nutrients, and yields. Much agricultural land has been degraded in tropical areas, typified by the loss of those characteristics which make forests so abundant–depleted soils, diminishing yields, lack of diversity. The problems of degraded lands are compounded by broadscale environmental influences such as erosion, watershed depletion, changing climate, and the presence of new diseases and insect pests.

Which species should be planted to help restore the natural abundance of a forest to degraded lands? Once a site has been degraded, it is often very difficult to predict which species will thrive there. The original forest species, if replanted, may not be able to cope in the changed conditions. It is usually unknown how other useful non-native species will behave in such circumstances. In other words, how a species will perform on a particular site is almost impossible to predict.

Farmers, ranchers and foresters have a history of selling products at the lowest market value. This is not sustainable, as it can force growers to push the land and themselves past a healthy threshold just to survive economically. Sustainable agriculture has to be about more than just how we treat the planet-- it has to create a day to day economic and personal reality that the grower can sustain healthfully.

"Value-added" is simply anything you can do to raise the value of your product in the market, anything you can add to it that enables you to increase your profit margin. Value-added practices often mean the difference between a farm that is economically viable and personally fulfilling, or one hat ultimately cannot be sustained financially or personally. Value-added practices are key to the future of sustainable farming, because they enable growers to advance economically without having to "pump up" the production of raw materials from the land.

Summary: There are numerous tropical perennial trees and shrubs with highly nutritious edible leaves. Such plants can form the foundation of a highly productive, low maintenance garden.

Most modern gardens have tended to focus on just a very few leafy edible species, the majority of which are short-lived annuals like lettuce, cabbage, and common spinach. Many of these are temperate species, which are poorly adapted to hot, humid conditions and require special tending and frequent replanting. Adding lesser-known tropical perennials to the garden contributes to diversity in the ecosystem and in the diet, while cutting down on the work to produce abundant quantities of nutritious leafy greens.

Apart from being ornamental and edible, many perennial vegetables can be grown on the edge of tree plantings, such as along paths. They can serve other functions around the house such as view screens (Pacific spinach, moringa), ground covers (sweet potato, bitter melon), and edge plants as a barrier to weeds (sissoo spinach, garlic chives). Many of these plants have medicinal as well as culinary utility.

(Note: Last issue, we highlighted the practice of Sequential Planting, or planting short-term crops in tree plantings to realize a return while waiting for long-term yields. This time, we focus on permanent interplanting of trees and crops in a layered agricultural system.)

Traditionally, tropical farmers have always managed and exploited the shady environment under trees, called the understory. There are many valuable cash and subsistence crops that thrive in the shady climate under trees. When cultivated in combination with tree or forest crops, understory crops enable farmers and foresters to diversify and increase their yields while reducing labor and making more efficient use of land. The understory is a niche worth cultivating.

Plantings that take advantage of the understory range from simple systems consisting of one species in the overstory and one in the understory, to complex systems with many layers of trees, shrubs, and herbaceous plants stacked together as appropriate for their needs.

Sequential Planting: Short-term returns combined with long-term plantings

Trees are the backbone of agroforestry plantings, but most trees represent a long-term investment. Fruit trees can take three to fifteen years to bear; timber trees usually need to grow twenty or more years before they can be harvested. These and other long-term tree resources are valuable and necessary, but most farmers cannot afford to devote their land entirely to a crop that will not yield for many years. Sequential planting, a practice wherein short-term crops are planted with and eventually replaced by long-term trees, is a system that enables farmers to invest for the future while making a return in the present.