YIELD AND DRY MATTER RESPONSE OF POTATO (SOLANUM TUBEROSUM) TO DIFFERENT NPK 17:17:17 FERTILIZER LEVELS IN MID ALTITUDE REGION IN UGANDA

Abstract

Potato is an important food and cash crop in Uganda that increasing its production and productivity must be emphasized. The yield and quality of potato tubers are partly influenced by the elevation and fertilizers used / nutrient level. There is an increased land degradation and low use of fertilizers by famers in Uganda leading to low potato yields and poor quality – dry matter. Most of the potato varieties in Uganda are bred for high altitude environments. In order to address these, this study was designed with the aim of establishing the yield and dry matter response of the potato in the mid altitude environment. The objectives of the study were to determine the yield output and dry matter content of potato varieties under different NPK 17:17:17 fertilizer levels; 0Kgs/ha, 50Kgs/ha and 100Kgs/ha. Three potato varieties; Victoria, Rwangume and Kachpot1 were studied for two seasons at BSU Farm Mbarara under a 4 x 4 factorial experiment arranged in a Randomized Complete Block design with three replications for each season. Soil analysis was carried out for the two sites. Results showed dry matter was significantly different among the varieties and the overall mean ranged from 17.06% to 23.7%. Across the seasons, Kacpot1 had the highest dry matter content at 22.96% from fertilizer level one whilst Rwangume had the lowest dry matter content at 18.08% from fertilizer level three, f3. The varieties were significantly different for; total tuber yield, average weight per tuber, tuber weight per plant, marketable/non-marketable tubers, biomass and number of tubers per plant. Fertilizer level three produced the highest overall mean of yield at 12.19 t/ha during Season I and the lowest over all mean at 5.3t/ha from fertilizer level f1 during Season II. Across the seasons, Katchpot1 yielded the best at 14.78 t/ha whilst Victoria was the lowest yielder at 7.02 t/ha. Fertilizer level three had the highest overall mean for number of tubers per plant at 11.1 during Season II. Across the seasons, Kachpot1 had the heaviest weight of tubers per plant at 369.5 g from fertilizer level f2 whilst Victoria had the lowest weight of xiv tubers per plant at 175.5 from fertilizer level f1. From this study, fertilizer requirements are also genotype specific. The output in the mid altitude area of Mbarara revealed lower yield and more none marketable tubers because the varieties studied were bred targeting highland areas of Uganda. There was a magnitude of genotype by environment interaction as indicated by the varied dry matter out puts per variety across the seasons and varying soil types. The fertilizer levels manipulated dry matter content with a steady reduction as more fertilizer of NPK 17:17:17 was applied. Fertilizer level f2 is recommended as optimum levels for optimum yield output. Further studies could focus on the interaction of different fertilizer levels and potato spacing, effect of potassium levels on dry matter content.