Site, Soil and Season of the Experiment
The experiment was conducted at the net house of Tuber Crops Research Centre, BARI, Gazipur during November, 2013 to March 2014. The location of the experimental site was to the 34 km north from Dhaka city (24.380 N latitude and 90.130 longitudes) at 8.4m above the sea level. The soil of the experimental field was grey terrace contained pH 6.4. This area is moderately drought prone, and face drought both winter and late winter season. The experimental site is situated in a sub- tropical climate zone and characterized by no rainfall during December to March.
Planting Materials and Date of Planting
Diseases free well sprouted seed potato minitubers of Diamant variety were used as planting material for the experiment. Mini-tubers were planted on 6th November, 2013.
Crop Management
The field was ploughed 3-4 times to a depth of 25 cm. Full doses of well rotten cow dung (10 t ha-1), TSP (220 kg ha-1), MP (270 kg ha-1), Gypsum (120 kg ha-1), Boric acid (6 kg ha-1) and half doses of Urea (175 kg ha-1) were applied at the time of final land preparation. The rest half dose of Urea (175 kg ha-1) was applied as side dressings at 30 DAP followed by earthing-up and light irrigation. First earthing up was done at 30 DAP when the plant attained a height of about 15-20 cm from the base, second earthing-up was done after 20 days of first earthing up. Before first earthing up, Urea was applied. Irrigation was applied 3 times. First one was applied just after planting, second one was just after earthing up at 30 DAP, and last one was on 55 DAP. During land preparation, Furadan 5G was applied @10 kg ha-1 as basal during land preparation and Admire (0.2%) was sprayed in two installments at 45 and 60 DAP to control insects. The crops were also sprayed alternatively with Dithane-M 45 (0.2%) and Secure (0.1%) at 15 days interval to prevent the late blight infection of potato. The field was netted during the entire growing period to protect the plants from the insect infestation specially aphids which is the vector of different viruses. Seeds were planted at row distance of 60 cm row and planting distance of 25, 20, 15 and 10 cm. Haulm pulling was done at 75 DAP by hand. Hardening and setting up of skins of tubers were allowed for 10 days under the soil there after crop was harvested at 85 DAP. Tubers were collected carefully with the help of spade without any injury.
Design and Treatments of the Experiment
The experiment was laid out in two factors Randomized Complete Block Design (RCBD) with three replications. First of all the entire experimental field was divided into three blocks, representing three replications. Each block again divided into twenty four unit plots. The treatment was assigned randomly to unit plots of each block. The size of a unit plot was 3.0 m × 2.4 m. There were six grades of minitubers based on minituber diameter (S1/Under size = <5 mm, S2/pea size=5-10 mm, S3/small size=10-15 mm, S4/medium size = 15-20 mm, S5/large size = 20-25 mm and S6/extra-large= > 25 mm) based on minituber diameter and four planting distance (D1=25 cm, D2=20 cm, D3=15 cm and D4=15 cm) which formed twenty four treatment combinations. Treatment combinations were as follows- S1D1, S1D2, S1D3, S1D4’ S2D1, S2D2, S2D3, S2D4, S3D1, S3D2, S3D3, S3D4, S4D1, S4D2, S4D3, S4D4, S5D1, S5D2, S5D3, S5D4, S6D1, S6D2, S6D3 and S6D4.
Data Collection
Data on different growth and yield contributing characters were recorded from the sample plants of each plot during the course of experiment. The sampling was done randomly. The plants in the outer row were excluded during random selection. Five plants were randomly selected from each plot to record the data on the following parameters: Plant emergence, plant height, leaf area, number and weight of tubers per plant, yield (kg m-2), and percentage of different grades of tuber by number, seed potentials and seed increase ratio.
Statistical Analysis
To find out the significance of experimental results, the collected data on different parameters were analyzed statistically by using MSTAT-C program. The mean for all the treatments were calculated and analysis of variance for ach parameter was performed by F-test. The mean separation was done by DMRT at 5% level of probability.