The volcanic ash soils of northern Ecuador have supported agricultural activities for thousands of years; however, at the dawn of a new millennium, in the peasant communities of Cotacachi, where crop yields have been declining over the past decades, the sustainability of agricultural production seems to be threatened. Within the SANREM CRSP, researchers Franz Zehetner and Bill Miller analyzed the fertility status of the soils in the Cotacachi area and identified limiting factors to crop growth in different zones of the area. The researchers used crop growth modeling to examine the long-term effects of nitrogen fertilization and residue management on maize yields, and to identify possible avenues for restoring and maintaining soil fertility as the basis of sustainable agricultural production.