Description of the experimental site. Geographical location and climateThe experiment was conducted during the period from October 2017 to April 2018.The present piece of research work was conducted in the experimental area of Sher-e-Bangla Agricultural University (SAU), Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh. The location of the site is 23074/N latitude and 900035/E longitude with an elevation of 8.2 meter from sea level. The geographical location of the experimental site was under the subtropical climate and its climatic conditions is characterized by heavy scanty rainfall during the rabi season. The soil belonged to “The Modhupur Tract”, AEZ-28 (FAO, 1988). The experimental area was flat having available irrigation and drainage system and above flood level.
Weather condition during the crop season
Details of meteorological data in respect of average temperature (0C), rainfall 231.3 (cm), relative humidity 77.5 (%) and sunshine hour 12:46 during course of studies i.e. from October 2017 to April 2018 has been presented in Appendix II.
BARI Bt Begun-2(Bt Kajla) and BARI Begun-4 (Kajla) were used as the test crop in this experiment. Seeds were collected from BARI (Bangladesh Agricultural Research Institute), Gazipur, Bangladesh.
Treatments of the experiment
Being a two-factor experiment, present study consists two factors such as variety and insecticide doses. Details of treatments are given below:
Factor Level Name Dose/ha
A 1 BARI Bt Begun-2(Bt Kajla
A 2 BARI Begun-4 (Kajla)
B 1 Absolute Control
B 2 Imidacloprid Admire [email protected] 0.5 mlL-1 of water
B 3 Spinosad Tracer 45 [email protected] 0.4 mlL-1 of water
B 4 Malathion Faythion 57 [email protected] of water
Experimental design and layout
The experiment was laid out in a factorial randomized complete block design (RCBD) with four replications, where the experimental area was divided into four blocks representing the replications to reduce soil hetero-genetic effects. Each block was divided into eight-unit plots as treatments demarked with raised bunds. Thus, the total numbers of plots were 32. The unit plot size was 3.6 m × 1.6 m. The distance maintained between two blocks and two plots were 0.5 m and 0.5 m, respectively. Layout plan of the experiment is given in appendix.
Land preparation and intercultural operation
Both varieties were sown on September 30, 2017. The plot selected for conducting the experiment was opened in the 3rd week of October 2017 with a power tiller, and left exposed to the sun for a week. After one week the land was harrowed, ploughed and cross-ploughed several times followed by laddering to obtain good tilth condition. Weeds and stubbles were removed. The experimental plot was partitioned into unit plots in accordance with the experimental design. Organic and inorganic manures as indicated below were mixed with the soil of each unit plot. Seedlings were transplanted on October 25, 2017. Irrigation (9 times) and drainage were provided when required. Weeding (5 times) was done to keep the plots free from weeds, which ultimately ensured better growth and development. Irrigation and weeding schedules are given in appendix
Fertilizers and manure application
The fertilizers N, P, K in the form of Urea, TSP, MoP respectively and S, Zn and B in the form of Gypsum, Zinc sulphate and Borax were applied as per recommendation of Bangladesh Agricultural Research Institute (BARI, 2013). Urea was applied as granule. The entire amount of TSP, MP, gypsum, zinc sulphate and borax were applied during the final preparation of land. The Urea was applied in four equal installments at Basal, 30 DAT, flowering and fruit setting.
Manure/Fertilizer Doses (kg/ha)
Basal 15 DAT Flowering Fruit setting
Cow dung 10000
Urea 60 60 60 60
Boric acid 10
Source: BARI 2013
To study pest succession in Bt and non-Bt brinjal varieties
Regular observations starting immediately after transplantation was carried out once in a standard week to record different insects of brinjal. The insects appearing on the crop right from transplantation up to harvest were recorded. The unprotected crops (absolute treatment) were used for this purpose. The sequence in which the insects appeared was also noted. The status of different insect pests recorded was determined on the basis of the damage caused by them. For observations, 5 plants from each plot were randomly selected and thus, 20 plants for each variety were selected and population of different insect pests and natural enemies thereon was assessed.