Optimization of nutrient solutions for enhanced yields and quality of potato (solanum tuberosum l.) rooted apical cuttings in hydroponics

Abstract

Potato (Solanum tuberosum L.) hydroponic system has been introduced to provide an avenue to potentially double potato productivity and lower seed production costs significantly. However, improperly constituted nutrient solutions for hydroponic seed potato production have often led to low yields due to either toxicities or deficiencies. The aim of this study was to optimize nutrient solution concentrations for enhanced growth, yield and quality of seed potato cultivars production in a hydroponic system. Two experiments were conducted in a greenhouse at Egerton University, Njoro, Kenya. A randomized complete block design in a split plot arrangement was used. The main plot treatment comprised of ‗ADC-Molo‘ nutrient stock solution concentrations (NSSC) (75% (N75), 100% (N100) and 125% (N125)) and the subplots comprised of rooted apical cuttings (ARC) of four potato varieties (Shangi, Wanjiku, Nyota and Unica). Data was collected from 5 tagged sample plants on growth, yield and quality parameters and subjected to Analysis of variance using SAS software version 9.4 and means separated using Tukey‘s Honest Significant Difference test at a probability level of p ≤0.05 level of significance. Results showed that the growth rate was significantly affected by the application of NSSC. Increasing the nutrient concentrations positively influenced plant height, Normalized Difference Vegetation Index (NDVI), plant survival and the above ground biomass. The varieties were also influenced with the application of nutrient concentrations with Nyota reporting the highest plant height, NDVI values at 60 days after planting (DAP) and the highest plant survival (%) at 75 DAP. On the other hand, Unica reported the lowest growth rates. Increasing the NSSC significantly increased minitubers number (plant-1) and yield per hectare (t ha-1). The highest number of minitubers (9.33) and yield (9.97t ha-1) were reported under the N125. Nyota (>7) and Wanjiku (>7) produced significantly higher number of minitubers per plant as compared to Shangi (>6) and Unica (>4). The highest yield per hectare was however reported in Unica (>7t ha-1) and Shangi produced the lowest yields (<5t ha-1). On the quality parameters, treatment N125 was significantly different from N100 and N75 and produced the highest starch content of 15.58ppm, specific gravity of 1.17 and the highest tuber dry matter content of 24.90%. Therefore, to achieve high rooted apical cuttings growth, yield and quality under a hydroponic system, this study recommends using 125% of the ADC Molo nutrient formulation to seed potato farmers. For developing highest minitubers numbers, Nyota and Wanjiku varieties are recommended.