The experiment was conducted at the experimental field of IWM Division of Bangladesh Agricultural Research Institute, Gazipur and at the farmer’s field of Kadamshahar, Godagari, Barind, Rajshahi during 2016-2017 and 2017-18. The soil was clay loam with field capacity (28.5-29%), and bulk density (1.44-1.48) gm/cc at both locations. The recommended dose of fertilizers was applied @ N250P55K110S40Zn5B1.5 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 a top dressing. The experiment was laid out in an RCBD design with three replications. The unit plot size was 5.0 m × 3.6 m. The treatments were selected based on irrigation application at different growth stages as stated below:
T1= Rainfed
T2= One irrigation at vegetative (25-30 DAP) stage
T3= One irrigation at pre-flowering (55-65 DAP) stage
T4=One irrigation at grain filling (90-100 DAP) stage
T5= Two irrigations each at pre-flowering (55-65 DAP) and grain filling (90-100 DAP) stages
T6= Three irrigations each at vegetative, pre-flowering and grain filling stages
The selected crop was maize and the variety was BARI (white grained) Hybrid maize-13. Seeds were sown on 11 December 2016 and 28 November 2017 at Joydebpur at a spacing of 20 cm plant to plant and 60 cm line to line and in farmer’s field of Kadamshahar, Godagari, Barind, Rajshahi seeds were sown on 28 November 2016 and 03 December 2017 at the same spacing. The crop was harvested on 7 May 2017 and 6 May 2018 at Joydebpur and 8 May 2017 and 16 May 2018 at Rajshahi.
The measured amount of water was applied to each plot as per treatment to maintain the soil moisture content in the root zone up to field capacity. Ten plants from each plot were selected randomly for the collection of data on growth, yield components and yield. Undesirable plants were rouged out. At physiological maturity, ears were harvested and then dried. After 4-5 days, sun drying, ears were dehusked and again dried for 2-3 days. The grain yield data was collected when the grain moisture was 13%.
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):
Where d = Depth of water applied (cm))
Fc = Field capacity of soil (%)
Mci = Moisture content of the soil at the time of irrigation (%)
As = Apparent specific gravity of the soil
D = Depth of root zone (cm)