Soil degradation is a major global environmental problem, causing widespread and serious impacts on water quality, biodiversity and the emission of climate changing greenhouse gases. The chemical and physical deterioration of soils also has major implications for agricultural productivity. According to a recent study, nearly 40 percent of the world's agricultural land experiences serious productivity impacts due to soil degradation, with rates up to 75 percent for some regions. (IFPRI, 2000) Yet a primary cause of soil degradation is the depletion of soils which results from the farming systems chosen by the farmers. Decisions such as where and when to produce, the types of techniques used - particularly in land preparation - and the level and timing of inputs, all affect the biophysical quality of the soil, and the extent to which it is depleted, conserved or augmented. Thus, although society and farmers themselves may benefit from higher levels of soil quality, it has proven difficult to achieve the changes in farm management practices necessary to reach this goal.

This seeming contradiction raises one of the key questions addressed in this paper: How do farmers make decisions about the management of the soil resources under their control? What incentives are they responding to, and what constraints do they encounter in this process?

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