Experimental site: The field experiment was conducted at the Germplasm Center of Agrotechnology Discipline, Khulna University, Khulna, during the period from September 2016 to March 2017. Experimental field was located at 89°34' E longitudes and 22°47' N latitude at an altitude of 8 meters above the sea level (FAO, 1988). The site is under the sub-tropical monsoon climate, which is characterized by heavy rainfall during Kharif season (April to September) and scanty of rainfall during rest Experimental site: The field experiment was conducted at the Germplasm Center of Agrotechnology Discipline, Khulna University, Khulna, during the period from September 2016 to March 2017. Experimental field was located at 89°34' E longitudes and 22°47' N latitude at an altitude of 8 meters above the sea level (FAO, 1988). The site is under the sub-tropical monsoon climate, which is characterized by heavy rainfall during Kharif season (April to September) and scanty of rainfall during rest.
Experimental materials, design of experiment and treatments: Cauliflower seed of snowball variety was collected from local market of Khulna, Bangladesh and seedlings were raised in 3m x 1m seedbed at the Germplasm Center, Agrotechnology Discipline, Khulna University, Khulna. Seeds were sown in line at a depth of 1.5-2.0 cm on 15th September, 15th October, 15th November and 15th December, 2016 respectively. Proper care was taken to ensure better germination of the seeds. Seedlings of 4 weeks old were transplanted at the main field. This experiment was laid out in a randomized complete block design (RCBD) with five replications for each treatment. The treatments included four planting times at an interval of 30 days from 15th October to 15th January as follows:
T1 = planting on: 15th October, T2 = planting on: 15th November, T3 = planting on: 15th December and T4 = planting on: 15th January.
The experimental area was first divided into five blocks which were again divided into 4 unit plots and thus the experiment consists of a total of 20 (4 x 5) unit plots. The size of a unit plot was 2.0 m x 4.0 m. The distance between two plots was 50 cm and a gap between two blocks was maintained as 75 cm.
A spacing of 50cm x 75cm was maintained during transplanting the seedlings. After transplanting of seedlings, various intercultural operations were accomplished for better growth and development of the plants. A few of gaps were filled by healthy seedlings of the same stock where initially planted seedlings failed to survive. Weeding and mulching were accomplished as and when necessary to keep the crop free from weeds and to conserve soil moisture. Irrigation was done daily until the plants were fully established and then every 2 days interval for 2 weeks. It was continued during curd initiation and also in curd enlargement stage.
Harvesting, sampling and data collection: Harvesting of curds was started at 105 days after transplanting. Data were recorded during harvesting from randomly selected five plants of each plot. Yields were recorded from the whole plot basis. Data were collected on plant height (cm), number of leaves/plant, leaf size (length and breadth) (cm), curd size (length and breadth), and yield (ton/ha). A cost-benefit analysis was made too from the collected data.
Yield (ton/ha): Total curd yield/plot was recorded from each plot. The gross (biological) yield and marketable (economic) yield were calculated from each plot and then converted to t/ha. Yield of whole plot with leaves, curds and stems was considered as biological yield. However yield of edible parts (curd) only was considered as economic yield.
Yield (ton/ha): Total curd yield/plot was recorded from each plot. The gross (biological) yield and marketable (economic) yield were calculated from each plot and then converted to t/ha. Yield of whole plot with leaves, curds and stems was considered as biological yield. However yield of edible parts (curd) only was considered as economic yield.
Cost–benefit analysis and benefit-cost ratio: The cost-benefit analysis was done based on gross returns and cost of production to compare the profitability among the treatments. The benefit-cost ratio (BCR) was calculated using following formula:
BCR= Gross Return / Cost of Production
Statistical analysis: Calculated data on various parameters under study were statistically analyzed using STAR statistical programme. Means for all the treatments were calculated and analyses of variances for all the characters under consideration were performed by F test. The significance of differences between pairs of treatment means were evaluated by New Duncan’s Multiple Range Test (Gomez and Gomez, 1984).