Sustainable Potato Production - Guidelines for - FAO.org

Diffuse light storage for seed potato tubersIn tropical areas such as theCentral African highlands, wherecold storage is unavailable or toocostly, smallholder growers storetheir seeds on the farm. Theefficiency of their simple homestorage facilities could bedramatically improved with useof diffuse light technology.Diffuse light stores (DLS) aremost suitable wheretemperatures are moderate (nofrost or extreme hightemperatures) and seed has to bestored for more than fourmonths. By using DLS, farmersare able to store their own seedstocks, instead of buying themfrom distant suppliers. However,the loading capacity of DLS islimited since all tubers must beexposed to the diffuse light.These stores are suitablegenerally for small seed unitsand not for large scale seedproduction schemes. Seedpotatoes stored in diffuse lightgive a more vigorous crop thanseed that has been stored forrelatively long periods in the darkat higher temperatures.However, the DLS must beprotected against aphids (e.g.with an aphid proof screen) toavoid the risk of infection andtransmission of viruses such aspotato virus Y and potato leaf rollvirus. Since the aphid populationincreases throughout the storagephase, stringent controlmeasures need to be put in placeto reduce seed degeneration.42SUSTAINABLEPOTATOPRODUCTIONCapacity-building for seed potato selectionA technique known as “positiveselection” was pilot-tested bysmallholder potato farmers in theNarok district of Kenya as a wayof improving the quality of theirseed potatoes. Positive selectioninvolves marking healthy-lookingmother plants for later seedcollection. More than 100extension workers and farmertrainerswere trained in allaspects of positive selection, andthen assigned to work with some1 200 farmers organized in 70farmer groups. A participatoryresearch approach was used, witha demonstration experimentforming the core of the trainingcurriculum. All activities tookplace in the potato field, and themode of teaching was “learningby doing”. The farmer groups metregularly, learning first how todistinguish between sick andhealthy-looking plants in thepotato field. Next, a comparativestudy divided the potato fieldwas into two parts: one wherepositive selection was used andone where the farmers used theirtraditional methods. Tubers fromthe two different selectionmethods were plantedseparately the next season, andthe group analysed the results.Within the positive selectionfield, potato yields increased onaverage by about 30 percent. Asurvey two years afterwardsshowed that more than onequarter of the farmers trainedhad adopted the positiveselection method. These farmersreported that their yields haddoubled.