The seeds of five T. Aman rice genotypes were used as experimental materials and those the seeds of those varieties were collected from various sources like as the local Farmers of the Patuakhali region, Branch office of Bangladesh Rice Research Institute (BRRI), Barisal and main branch of BRRI, Joydebpur, Gazipur–1701. The selected five Aromatic T. Aman rice genotypes are
V1: BRRI dhan–44
V2: Lalchicon
V3: Lalmota
V4: Moulata
V5: Mothamota
The experiment consisted of five rice varieties and was laid out in Randomized Completely Block Design (RCBD) with three replications. The size of plot was 4.0 × 2.5 m where block to block and plot to plot distance was 1.0 and 0.5 m, respectively. Row to row and plant to plant distance were also 20 and 20 cm, respectively, in each plot. So, the total plots were 15 (varieties 5 × replication 3).The seeds were soaked for 24 hours and then these were kept in a gunny bag in dark condition. After sprouting, the seeds were sown in the previously prepared wet seed bed on 21 June 2013.On 30th July 2013, 39 day–old seedlings were transplanted in the experiment field keeping plant to plant distance 20 cm and row to row distance 20 cm.
Sampling was done at 15 days interval from 30 DAT up to 60 DAT and harvest for morpho–physiological data and at harvest for yield and yield contributing data. At each sampling five random hills from each plot were uprooted avoiding border hills and washed them in running tap water. Then the plant samples were carried to the laboratory and plant height, number of tillers and other necessary morpho–physiological data were recorded. Yield and yield contributing data were recorded after harvest and the grain and straw yield data were also recorded at 12% moisture basis.
Leaf area index (LAI)
The leaf area of one hill was measured by an automatic leaf area meter. Leaf area of the rest five hills were calculated from the leaf dry weight of respective hills multiplying with the ratio of the leaf area of measured hills and its dry weight. Then the leaf area was expressed as average of five. Finally leaf area index (LAI) was calculated as follows-
Where, LA = leaf area (cm2), P = ground area (20 cm × 15 cm = 300 cm2 plant-1)
Total dry matter (TDM) weight
The plant parts such as leaves, stems, roots and panicles were detached and were kept separately in oven at 82O C for 72 hours. The oven dried samples were weighed for dry matter production. The total dry matter production was calculated from the summation of dry matter produced by leaves, stem, roots, panicles and weight of grain per plants in gram at different days after transplanting.
Crop growth rate (CGR)
The CGR value of crops were calculated for the period of 60-75 DAT and 75-90 DAT. Rate of dry matter production per unit of time per unit of ground area was calculated with the following formula:
Panicle length (cm)
Panicle length was measured by a meter scale from the basal node of the rachis to the apex of each panicle from the randomly selected 5 hills and their average was recorded and converted into cm.
Number of total grains panicle–1
Number of total grains panicle–1 were recorded by the following formula
Number of total grains= Number of filled grains + number of unfilled grains
Number of filled grains panicle–1
Filled grain was considered to be filled if any kernel was present there in. Number of filled grain was recorded from randomly selected 5 hills and converted into filled grains panicle–1.
Number of unfilled grain panicle–1
Number of unfilled grains panicle–1 means the absence of any kernel inside in and such grains present on each hill were counted from the randomly selected 5 hill.
1000–grain weight (g)
One thousand cleaned dried seeds were counted randomly from each sample and weighed by using a digital electric balance at the stage the grain retained 12% moisture and the mean weight were expressed in gram.
Grain yield (t ha–1)
Grain yield was determined from the whole plot and expressed as t ha–1 on 12% moisture basis. Grain moisture content was measured by using a digital moisture tester.
Straw yield (t ha–1)
Straw yield was determined from the whole plot. After threshing, the sub–sample was oven dried to a constant weight and finally converted to t ha–1.
Biological yield (t ha–1)
Biological yield is the sum of grain and straw yield which was recorded into kg plot–1 and finally converted into t ha–1. The biological yield was calculated by using the following formula:
Biological yield= Grain yield + straw yield
Harvest index (%)
Harvest index is the ratio of the economic yield to the total biological yield of a crop. The harvest index was calculated by using the following formula:
Harvest index (%) =
Where, Economic yield = Grain yield
Biological yield = Grain yield + Straw yield