2.1. Experimental site and soil The experiment was conducted at the research field in Jute Agriculture Experimental Station, Manikganj, during the month of August to December, 2019 in order to study the effect of herbicide application time on morpho-physiology, yield attributes and seed quality of two jute varieties e.g., BJRI tossa pat-8 (Corchorus olitorius L.) and CVL-1 (Corchorus capsularis L.). The experimental field was medium high land belonging to Old Brahmaputra-Jamuna flood plain (AEZ-8) having silt loam soil with pH 6.5. The soil contained 1.6% organic matter, 0.08% total nitrogen, 7.65 ppm available P, 0.23 meq. K 100g-1, and 12.87 ppm available S.
2.2. Experimental treatments and design This study consists of two jute varieties e.g., BJRI tossa pat-8 and CVL-1 and three different herbicide application time (T0: Control, T1: 10 days after cutting transplanting, T2: 13 days after cutting transplanting, T3: 16 days after cutting transplanting). For cutting 100 days old mother plant were used because in previous study showed 100 days old mother plant gave better yield (Alam et al., 2019). Experiment was conducted in Randomized Complete Block Design (RCBD) with three replications. In this study two post emergence herbicide sprayed separately in experimental field. Ethoxysulfuron and quizalofop Ethyl are active ingredients of the herbicide. Ghorai et al., 2004 reported that the quizalofop ethyl was effective in controlling grassy weeds of Jute. Dose of herbicide were determined according to manual of herbicide.
2.3. Land preparation and crop management The experimental field was prepared with three ploughing and cross ploughing followed by laddering. The unit plot size was 2m X 2m. Plot to plot distance was 1 meter. The crop was fertilized with nitrogen, phosphorus, potash, boron and sulfur as per the recommendation dose for jute seed production. Two weeding were done in T0 treatment first one in 20 days after cutting transplanting and second one in 45 days after cutting transplanting. For all other treatments no weeding was done. All other intercultural operations were done as per requirement.
2.4. Harvesting and plant sampling When the matured seed (about 80% seed matures) of jute turned into blackish in color the plant sample were collected from each plot in treatment wise with proper tagged. Ten randomly selected plants were taken from each plot for getting accurate data. After threshing of capsule, seeds were cleaned and sun dried.
2.5. Morpho-physiological characters, yield & yield attributes Morpho-physiological characters namely plant height (m) was measured with the help of scale meter. On the other hand yield and yield attributes viz. capsule length (mm), capsule/plant, seeds/capsule, 1000 seed weight and seed yield (t/ha) were determined by the standard method.
2.6. Seed quality After threshing, sun dried seed were taken for quality testing with 9% moisture. For germination seeds were surface-sterilized first by a fungicide treatment (1 g L–1 Benlate) for 30 min, immersed in 6% calcium hypochlorite solution for 5 min, and then rinsed in 70% ethanol for 5 min and thoroughly washed with sterilized distilled water. Seeds were plated onto glass petri dishes (9 cm in diameter) containing sterile perlite and placed in a growth chamber where the temperature and humidity were 25 °C and 80%, respectively, with a photoperiod of 16 h day–1. Lighting was provided by OSRAM L36W/77 type lamps (FLUORA, white fluorescent tubes) providing an intensity of 1500 μmol h–1 photon–1. Each petri dish contained 100 seeds. The parameters of the germination capacity (GC), germination kinetics, i.e. the mean germination time (MGT), the coefficient of velocity of germination (CVG), seed vigour, field emergence was determined by following formulas.
1) Germination capacity (GC)
GC% = n/N* 100
Here, n is the total number of germinated seeds and N is the total number of tested seeds.
2) The coefficient of velocity of germination
(CVG) CVG = 100 × ΣNi / ΣNiTi
Ni = Number of germinated seeds per day and Ti = Number of days from the start of the experiment