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Increasing human population densities have, throughout history, resulted in land use intensification, i.e. an increasing frequency of agricultural production in space and time until land is permanently cropped. Higher outputs per unit land area require increased inputs of human and fossil energy, nutrients and biochemicals. If these external inputs are unavailable, land use intensification may lead to soil mining and low production levels. Only two systems of traditional, low input farming in the humid tropics have evolved under conditions of high population densities: wet rice cultivation and homegardening. In different ways, both systems allow some degree of soil fertility and pathogen management under permanent land use. The agronomic aspects of wet rice systems have been studied extensively, but surprisingly little is known in comparison of homegardens.