They are equalled in their productive capacity only by the highest terraces on the slopes of Cerro Gordo in the same region, and their production approaches that of the irrigated lands in the Lower Valley. The significance of the presas for agriculture stems from the humidity retention capacity they possess and their ideal location for trapping both soil … and water. … it is very rare that a crop is lost in the presas … Maize is planted as early as February in some presas. Special planting techniques are also applied to the presas to make available subsoil moisture.