The experiment was conducted during rabi season of 2014-2015 at the research field of the Regional Agricultural Research station, Ishurdi, Pabna. The experimental field soil was silty clay loam having field capacity of 28%, permanent wilting point of 13% and bulk density of 1.49 g cm-3. The experiment was conducted using a Randomized Complete Block Design with four replications. BARI Gom-28 was sown in individual plot of size 7 × 7.5 m, on raised bed with 40 cm base width, 20 cm top width, 15 cm height and 20 cm distance between two beds. The beds were formed by bed planter and were subjected to the following treatments.
T1 = Three irrigation at 17-21 DAS, 55-60 DAS and 75-80 DAS (Full Irrigation)
T2 = Irrigation at 30% soil moisture depletion (SMD)
T3 = Irrigation at 50% soil moisture depletion (SMD)
T4 = Irrigation at 60% soil moisture depletion (SMD)
Seeds were sown on 24 November 2014 and harvested on 23 March 2015. SMD was determined by monitoring soil moisture contents. For this purpose, soil samples were taken from the effective root-zone of the wheat plant (0 – 90 cm). The root-zone was divided into 3 depths viz., 0-15, 15-30 and 30-45 cm. Soil samples were collected from these 3 depths with the help of an Augur. The fresh weight of the soil sample was immediately recorded with the help of a portable weighing balance. After weighting, the samples were stored in soil sampling core which were then placed in an electric oven for 24 hour at 100°C. The dry weight of the samples was then recorded. Irrigation water was applied up to field capacity at each irrigation. The amount of water applied to each treatment was calculated on the basis of the soil moisture contents at the time of irrigation.
d = Fc-Mc/100 x As x Bd
Where,
d = Depth of water to be applied (cm)
MC = Moisture content (%) at the time of irrigation (FC-MCi)
A.S = Apparent specific gravity of soil
D = Depth of root-zone to be irrigated (cm)
F.C = Moisture content at field capacity of soil (%)
MCi = Moisture content at the time of irrigation (%)
The depth of rooting was considered 45 cm. It is reported that 70 % of total moisture is extracted from the 50 % effective root zone depth (Michael, 1996). The seasonal crop water use was calculated. All other agronomic practices were carried out uniformly. At maturity, data were collected on grain yield. Water use efficiency was used in evaluating the yield performance and water management practices. The water utilized by the crop was calculated