ABSTRACT
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Some 30 years ago, a number of agronomists around the world independently realized
that chemical fertilizers had become a tremendous financial drain for smallholders. At the
same time, they realized that composting takes more labor than will be invested in most
extensive subsistence crops; and animal manure, at least among the poor, is usually
unavailable or too limited to maintain soil fertility levels. Furthermore, there had been no
significant adoption of conventional green-manuring practices by smallholders. So a
search began for new, less expensive ways that smallholders could maintain or increase
the fertility of their soils. This research focused on agroforestry systems (Chapters 19, 20
and 21) and in what are now referred to as green manure/cover crops (GMCCs). These
systems have achieved, to a remarkable degree, their goal of offering farmers widely
applicable systems that canmaintain or increase soil fertility in the tropics where rainfall is
adequate, at little or no cost.
