Sustainable Potato Production - Guidelines for - FAO.org

and quality losses. They include croprotation, use of resistant varieties andhealthy, certified seed tubers (if available orat least seed from a reputed source orthrough positive selection), and integrateddisease and insect pest management, whichinvolves regular monitoring of aphid andthrips vectors, other insects and naturalenemy populations, and chemical sprayingonly when necessary.Fertilizer application during the stagesof pre-planting, planting or crop growthshould be determined by soil nutrientavailability, taking into account thepotato’s high demand for potassium,phosphorus and magnesium deficienciesin acid soils. The NPK ratio 1-1-1 is usuallya wise choice to avoid spoiling tuberquality. The potato can benefit from theapplication of organic manure at the startof a new rotation as it provides a goodnutrient balance and protects soil structurefrom compaction and erosion.As soil moisture must be maintained at arelatively high level in production ofpotatoes, compared to other crops, irrigationmay be required where rainfall is limited.HarvestingFor most commercial varieties, yellowing ofthe potato plant’s leaves and easy separationof tubers from stolons indicate that thepotato crop has reached maturity. If thepotatoes are to be stored rather thanconsumed immediately, they are left in thesoil to allow their skin to harden – hard skinalso help seed potatoes to resist storagediseases. However, leaving tubers for toolong in the ground increases their exposureto the fungal disease black scurf andincreases the risk of losing quality andmarketable yield.To facilitate harvesting and stop tubergrowth, potato vines should be removed twoweeks before the potatoes are dug up.Depending on the scale of the production,potatoes are harvested using a spading fork,a plough or commercial potato harvestersthat unearth the plant and shake or blowthe soil from the tubers. During harvesting,especially if it is done mechanically, it isimportant to avoid bruising or otherinjuries, which provide entry points forstorage diseases and reduce the commercial,processing quality and storability of thetubers.In suitable environments and wheregrowing conditions are adequate,commercial yields are in the range of 40–60tonnes per hectare. In many developingcountries, however, they are far below thisfigure, with national averages of about 10-20 tonnes per hectare.27GOODAGRICULTURALPRATICESAND POTATOPRODUCTION