The experiment was conducted at the experimental field IWM Division of Bangladesh Agricultural Research Institute, Gazipur during 2012-2013 and 2013-2014 and RARS, Ishwardi during 2013-2014. The soil was sandy clay loam with field capacity (28.5-29%), and bulk density (1.44-1.48) gm/cc at both the locations. Parental lines of BARI Hybrid Maize 9 (BIL79 x BIL28) were sown in isolation (time) maintaining ratio of four female rows alternate with two male rows (4:2). Male rows were sown in two different dates for synchronization. Recommended dose of fertilizers were applied @ N120P80K80S20Zn5B2 kg/ha and CD @ 5 t/ha. Full doses of P, K, S, Zn, B and cowdung were applied at the time of final land preparation. Nitrogen was applied in equal three splits, 1/3rd amount of urea-N was applied at the time of final land preparation and the rest of the urea-N was applied in equal two installments as top dress. The experiment was laid out in a RCBD design with four replications. The unit plot size was 7.2 m × 4.0 m. The treatments were selected based on irrigation application at different growth stages as stated below:
Treatments
T1= Two irrigation each at vegetative stage (50-60 DAS) and grain filling (110-120 DAS) stages
T2= Two irrigation each at silking stage (80-90 DAS) and grain filling (110-120 DAS) stages
T3= Three irrigation each at vegetative stage, silking and grain filling stages
T4= Four irrigation each at early vegetative (20-25 DAS), vegetative, silking and grain filling stages
Seeds were sown on 18 and 24 November, 2013 at Joydebpur. Only two lines of male seeds were sown on 18 November, 2013 and the other two lines of male and eight lines of female seeds were sown on 24 November, 2013 at a spacing of 20 cm plant to plant and 60 cm line to line. The two lines of male seeds were sown on 19 November, 2013 and the other two lines of male and eight lines of female seeds were sown on 25 November, 2013 at the same spacing at Ishurdi. The crop was harvested on 24 April 2014 at Joydebpur and 5 May 2014 at Ishurdi. Measured amount of water was applied to each plot as per treatment to maintain the soil moisture content in the root zone (30, 40, 50, and 60 cm) up to field capacity. Ten plants from each plot were selected randomly for collection of data on growth, yield components and seed yield. At flowering time, all the female plants were detasseled before anthesis. Undesirable plants of both male and female parents were rouged out. At physiological maturity, ears were harvested from the male and female rows separately and then dried. After 4-5 days, sun drying, ears were shelled and again dried for 2-3 days and preserved in the cool room having temperature range 100C - 140C for future use.
Estimation of irrigation water
Irrigation water was applied to bring the soil moisture content at the root zone to field capacity taking into account the effective root zone depth. Irrigation water was calculated using the following equation (Michael, 1985):
d = Fc--Mci/100 xAs x D
Where, d = Depth of water applied (cm)
Fc = Field capacity moisture content (%)
Mci = Moisture content of the soil at the time of irrigation (%)
As = Apparent specific gravity of the soil
D = Depth of root zone (cm)