The experimental trial on wheat (variety: BARI Gom- 25) was carried out in the open field during 2014–2015 and 2015 –2016 at the experimental field of IWM Division of Bangladesh Agricultural Research Institute, Gazipur. The soil was sandy clay loam with FC and BD of 28.5% and 1.36 g/cc, respectively. Wheat seeds were sown on 31 November 2015 and 04 December 2016 at a spacing of 20 cm between rows at a seed rate of 120 kg/ha. The unit plot size was 2m ´ 1.8m. The experimental plots were fertilized with N90, P13 and K25 kg ha-1 in the form of Urea, TSP and MOP respectively. All the fertilizers and one-third of urea were applied during final land preparation and the rest of urea was applied in two equal splits as top-dressing at 20, and 40 days after sowing. Prior to sowing, NaCl was mixed with the soil to obtain the desired salinity levels of about 5 dS/m to synchronize with the salinity of coastal areas at sowing time. The quantities of water and corresponding NaCl requirement to obtain a given salinity level were calculated using the equation suggested by USDA (1954). In a completely randomized block design, with three replications, five levels of salinity treatments were compared with a freshwater control treatment. The crop received four irrigations each at 20, 40, 60 and 80 days after sowing (DAS). The plots were irrigated up to 100 % of field capacity (F.C.). Among the salinity treatments, four fixed levels and one varying level of saline irrigation water were as follows:
T1= Irrigation with freshwater (< 0.5 dS/m)
T2= Irrigation with water having a salinity of 4 dS/m
T3= Irrigation with water having salinity of 7 dS/m
T4= Irrigation with water having salinity of 10 dS/m
T5= Irrigation with water having salinity of 13 dS/m
T6=Irrigation with water having salinity of 4, 7, 10, 13 dS/m at 20, 40, 60 and 80 DAS
The soil salinity of the plots was measured five times at sowing, after 3 days of each irrigation and at harvest by a portable EC meter. All the physiological and yield contributing characters of wheat were recorded. During the cropping season, leaf area index and aboveground biomass were determined at successive phrenological stages. Ten plants were cut at ground level and chosen as samples. Then the plant samples were divided into leaves and stems. The leaf area of each plot sample was measured by a leaf area meter. Then the leaves and stems were oven-dried at 70 °C for 48 hours to obtain the weight of above-ground biomass. Biomass was also estimated at the time of harvest. The crops were harvested on 21 March 2016 and 25 March 2015 at hard maturity and manually threshed with 100% grain recovery. The number of spikes per square meter, spike length, spikelet per spike, number and weight of grain per spike, 1000- grain weight, grain and biological yield were recorded at harvest. Harvest index was calculated by dividing grain yield by biological yield, which was the sum of dry grain weight and dry shoot weight at each harvest sample. The root biomass was measured at harvest from half of unit soil strip on 30 cm x 20 cm soil surface in the depth increment of 20 cm up to 60 cm, keeping 30 cm row in the middle (Kumar et al., 1993). Finally, analysis of variance of the growth and yield parameters of wheat was done for the RCBD design using MSTAT-C.