In the Central Peruvian highlands, potatoes are commonly cultivated by smallholder farmers in fields between 3500 and 4300 m asl. Severe climatic conditions, marginal soils and limited access to inputs and infrastructure define these challenging agro-ecological environments. To prepare an adequate seed bed for the potato and mitigate climatic, topographic and labour constraints, Andean farmers have developed distinct footplough-based tillage systems: barbecho, chiwa and chacmeo. A series of field experiments was conducted in 2005/06 and 2006/07 at four different locations to investigate the effect of three different tillage systems on potato tuber yield, varying factors such as cultivars and types and amounts of fertilizer applied. The objective was to improve understanding of the effect of these factors on potato yield and study the potential advantages and disadvantages of each tillage system.
The study showed that the type of tillage influenced a great variety of factors. Farmers often use a combination of tillage systems as a strategy to diversify possible risks, considering trade-offs regarding productivity v. yield stability, internal v. external resource use, labour requirement during peak times v. more uniform distribution or extensive v. intensive production. The chiwa and to some extent the chacmeo tillage systems resulted in relatively constant and stable yields for different environments and genetic materials, whereas the more intensive barbecho system sought to optimize growth conditions for the potato crop but was more liable to stress and required external resources. Currently, farmers often use the barbecho system to produce commercial cultivars for the urban markets investing the greatest share of internal and external resources. They use the chiwa and chacmeo systems to produce diverse native cultivars for their home consumption, valorizing their taste, cooking qualities and lower resource requirements.