Time and location:
The experiment was conducted at the research field of Agriculture department, Noakhali Science and Technology University (NSTU), Noakhali-3814 from November 2018 to May 2019. The experimental field is under the agro-ecological region of the Young Meghna Estuarine Floodplain (AEZ-18). The land was almost level having sandy loam soil and moderately alkaline (SRDI, Noakhali), with pH value 7.5 and electrical conductivity 0.91 dS/m. A pH Meter (Hach sensION+ PH1 Basic Portable pH Meter) and an EC meter (sensION+ EC7) were used to measure pH and electrical conductivity respectively. The experimental area is under the tropical climate with an average annual temperature of 25.6 °C and the average annual rainfall about 3,302 mm (Weather Station, Maizdee, Noakhali).
Experimental design:
Two factors included in the experiment were as follows: Factor A: Variety (2); V1- BINA dhan-8, V2 - BRRI dhan-67 and Factor B: Treatments (3); T1- 250 kg Urea/ ha, T2- 150 kg Urea/ ha, T3- 120 kg Urea/ ha. Seeds of BINA dhan-8 were collected from Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh-2202 and BRRI dhan-67 were collected from Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. The size of each unit plot was 3.0 m × 2.0 m, having an area of 6 m2. So, the total number of the unit plot was 18 (3×3×2). A spacing of 50 cm and 80 cm was maintained between the replications and unit plot respectively.
Seedlings establishment:
The seeds were soaked in the water for 24 hours and then were taken out of the water, covered with wet gunny bags and then kept for sprouting. After 48 hours’ seeds were started sprouting and almost all seeds were sprouted after 72 hours. Pre-germinated seeds of the two varieties were broadcasted uniformly in a well-prepared nursery bed on 16 December 2018.
Final land preparation:
Plowing and cross-plowing was done by a tractor to prepare the land and subsequently laddering to level the land. The field was fertilized with Triple Super Phosphate (TSP), Muriate of Potash (MoP) and Gypsum at the rate of 120 kg, 80 kg and 60 kg per hector respectively during land preparation. Urea was applied (as per treatment) as top dressing in three equal splits at 15, 30 and 45 days after transplanting (DAT).
Seedlings transplanting:
Before uprooting the seedlings, nursery bed was slightly irrigated for easier uprooting. Uprooting of seedlings were done carefully from the nursery bed and were transplanted in the unit plots on 25 January 2019 where spacing was maintained at 25 cm × 15 cm (row to row and plant to plant) at the rate of 1-2 seedlings/hill. Hand weeding was done at 20 and 35 days after transplanting (DAT). The field was irrigated from the nearest water source (pond) by irrigation devices when necessary. A regular observation was made to ensure better growth of plants.
Collection and analysis of data:
Randomly ten hills (excluding border hills) were selected from each unit plot and uprooted before harvesting for data collection. The harvested crop of each unit plot was bundled separately, tagged properly, brought to the threshing floor and then threshed by a pedal thrasher. Grain and straw were sun-dried at 14% moisture level and cleaned. Data were collected on plant height (cm), tillers/hill, grain/panicle, 1000 grain weight (g), grain yield (t/ha), straw yield (t/ha) and harvest index (%). Plant height (selected ten plants) was measured from the base to the tip of the longest panicle. Tiller comprising at least one visible leaf were counted. Spikelet that contain any food material was considered as grain and the number of grain in each panicle was counted. One thousand clean dried seed from the seed lot of each unit plot were counted separately and weight by an electrical balance. The recorded grain and straw yield per plot was finally converted to t/ha. Harvest index (%) was calculated with the following formula. Harvest index (%) = (Grain yield ÷ Biological yield) × 100.
Where, Biological yield = Grain yield + Straw yield.
Data recorded for growth, yield and yield contributing characters were compiled and tabulated in proper form for statistical analysis. Analysis of variance was done with the help of MSTAT-C computer package program developed by Russel (1986). The mean differences among the treatments were adjudged by DMRT test (Gomez, 1984).