Yield and nutrient removal in potato-based conservation agriculture cropping systems in the high altitude andean region of Ecuador

The Illangama region of Ecuador’s highlands is typical of much of the Andean region throughout South and Central America. Steep slopes, frequent soil disturbance and the short fallow periods threaten the sustainability of soil quality and crop production in this region. We evaluated several conservation agricultural practices, including deviation ditches, crop residue retention, and reduced tillage in the context of a potato (Sola-num tuberosum L.)–oat/vetch (Avena sativa L./Vicia sativa L.)–barley (Hordeum vulgare L.)–faba bean (Vicia faba L.) rotation from 2011 to 2014 on crop productivity, crop and soil nutrient concentration, and nutrient removal from the system. Crop productivity tended to be higher in plots that had deviation ditches, and where crop and cover residues were retained in the field. Reduced tillage systems had yields similar to conventional tillage systems in all crops. Retaining crop and cover crop residues in the field had the greatest impact on recycling nutrients back to the soil, but was also the most costly conservation practice that we evaluated. Overall, conservation agricultural practices showed considerable agronomic promise for cropping systems in the Illangama region of Ecuador, but will require a longer evaluation period and a comprehensive outreach plan to help gain acceptance with regional farmers. Retaining crop and cover crops residues in the field rather than for animal fodder will make the greatest contribution to soil nutrient cycling, but likely to be the least accepted conservation agriculture (CA) practice evaluated in this study.