Research Location The research was conducted at the Agronomy Research Field of Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh during the period from November 1, 2016, to April 30, 2017. Topsoil was silty clay in texture, olive-gray with common fine to medium distinct dark yellowish-brown mottles. Soil pH was 5.6 and had organic carbon 0.45%. The selected plot was medium-high land. Plenty of sunshine and moderately low temperature prevails during the experimental period, which is suitable for potato growing in Bangladesh.
Experimental Design The experiment consisted of two factors. Factor A: Potato varieties (V1-4) - V1: BARI TPS-1, V2:BARI Alu-28 (Lady Rosetta), V3: BARI Alu-25 (Asterix), V4:BARI Alu29 (Courage); Factor B: Vermicompost levels (M1-4) - M1: 0 t ha-1 (control), M2: 2 t ha-1 , M3: 4 t ha-1 , M4: 6 t ha-1 . The experiment was provoked in a split-plot design with three replications. The variety was assigned to the main plot and vermicompost to the subplot. The distance between row to row was 50 cm, plant to plant was 25 cm and plot to plot was 75 cm. The size of the unit plot was 2 m × 2.5 m.
Crop Management Collected all varieties of seed potatoes were certified seed and the individual weight of seed potato was 60-70 g. The experimental soil was fertilized with Urea (250 kg ha-1), Triple Super Phosphate (150 kg ha-1), Muriate of Potash (250 kg ha-1), Gypsum (120 kg ha-1), Zinc Sulphate (10 kg ha-1) and Boric Acid (10 kg ha-1) as recommended by Mondal et al., (2011). The total amount of vermicompost was applied at 7 days before planting as per treatment. The well sprouted healthy and uniform sized potato tubers were planted according to 4-5 cm depth in soil. Different intercultural operations such as irrigation, weeding, mulching, earthing up and plant protection measures were done as per when needed. Haulm cutting was done at 85 DAP, when 40-50% of plants showed senescence and the tops started drying. After haulm cutting the tubers were kept under the soil for 10 days for skin hardening. The potatoes of each plot were separately harvested, bagged and tagged and brought to the laboratory.
Recording of Data The following data were collected during the experiment from the laboratory where the potatoes were stored with a good ventilation facility. Dry Matter Content (%) The samples of tuber were collected from each treatment. After peeling off the tubers the samples were dried in an oven at 72°C for 72 hours. Dry matter content was calculated as the ratio between dry and fresh weight and expressed as a percentage (Barton, 1989).
Specific Gravity (g cm-3 ) It was measured by using the following formula –
Specific gravity = Weight of tuber in air (g) / Weight of tuber in air - Weight of tuber in fresh water at 4°C
Statistical Data Analysis The data obtained for different characters were statistically analyzed following the analysis of variance (ANOVA) techniques by using Statistix 10 (2013) computer package program. The significant differences among the treatment means were compared by Least Significant Difference (LSD) at 5% level of probability (Gomez and Gomez 1984). The correlation was calculated on the basis of data from 0 days of storage, i.e. at harvesting day. The correlation graph was plotted with the help of Microsoft Excel 2016.