Integration of Irrigation Water and Mineral Nutrient Supply Effects On Firmness and Total Soluble Solids Content of Seed Potato (Solanum tuberosum L.).


Gathungu, G.K., Aguyoh, J. N. and Isutsa, D. K. 2013.




Potato (Solanum tuberosum L.) is of significant economic and nutritional importance in many countries. Establishment of good fertility, proper nitrogen, phosphorus and potassium fertilisation together with adequate water supply is critical in improvement of seed potato quality. Trials were conducted from August 2011 on a Farmat Egerton University to determine the effects of irrigation water, nitrogen (N) and phosphorus (P) on qualityofseedpotatoes.Thethreefactorsweretested in a split-split plot design with irrigation water assigned tomain plots,N to subplots and P to sub-subplots.The treatments were replicated three times and repeated once. Thetreatmentsconsistedofthreeirrigationrates (40%,65% and 100% field capacity),applied through out the potato growth period in drip tubelines. Water was supplied to root zones only,leaving the inter-row spaces dry.Nitrogen was supplied asurea (46%N) at fourrates (0, 75, 112.5 and 150 kg N/ha), each in two splits, with the first half at planting and the second at 5 weeks after planting. Phosphorus was supplied at planting time as triplesuperphosphate(46%P2O5)atfourrates(0,115, 172.5and230kgP2O5/ha),translating to 0,50.6,75.9, 101.2kgP/ha.Analysisofvariancerevealedsignificant differences in firmness and total solublesolids(TSS) asaffectedbyirrigationwater,NandP supply.High irrigation water resulted inrelatively low firmness (9.23 and10.17),comparedtolowirrigationwater,whichhad highfirmness(10.43and11.44)inbothtrials. Thelow N supply improved firmness (9.51 and  10.31),while the lowP ratereducedfirmnessoftheseedpotatoes(9.07 and9.98). While high irrigation water supply reduced TSS,highsupplyofbothPandNincreasedTSS.The 100%irrigationwater(5.48and5.52)andbothlowN byP supply(5.33and5.49)resultedinrelativelylow TSS, compared to 40% irrigation water (6.00 and 6.06) andhighNbyPsupply(5.66and5.93)inbothtrials.It isrecommendedtoapplylowirrigationwaterandNbut highPtoincreasefirmnessthatreducessusceptibilityof seed potatoes to mechanical injury and decayinstorage, leading to low deterioration. In addition, low irrigation water plus high N and P should be supplied to increase TSS content that enhances seed potato tuber physiology and growth of resulting potato plants.

Key Words:Potato,water,mineralnutrients,firmness, total soluble solids

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