Pathways to Agroecological Intensification of Soil Fertility Management by Smallholder Farmers in the Andean Highlands

Small farmers in the high Andes (>2500m) of Bolivia, Ecuador, and Peru face increasing threats to their livelihoods due to land degradation, climate change, and overall decreases in agricultural productivity. The fragile nature of these agroecosystems and limited capacity of resource-poor farmers in the region to adopt the large-scale use of conventional fertilizer and pest control technologies suggest the need for agroecological intensification to restore soil functioning and ensure long-term sustainability in these systems. This review addresses soil fertility decline from a management perspective and considers six basic approaches to enhance nutrient cycling, crop nutrient acquisition, and long-term productivity. A mass balance approach first defines basic boundaries for nutrient cycling and suggests that erosion control and identification of alternative nutrient sources (e.g., peri-urban wastes, rock phosphate) are critical for reversing negative nutrient budgets. Meanwhile, short-term nutrient dynamics could benefit greatly from improved management of organic residues in combination with low-level inorganic fertilizer applications. There is also a need for greater understanding of soil physiochemical properties throughout much of the Andes and the impacts of management. Similarly, soil biological functioning is critical for successful agroecological intensification and there is great potential for both inoculative and management strategies to promote beneficial soil communities. Crop breeding for smallholder environments should complement strategies of agroecological intensification, taking advantage of high regional agrobiodiversity and experience from stress breeding programs in other regions. Finally, we suggest several means by which the spatial and temporal organization of farms may be improved to enhance overall agroecosystem function.