The experimental trial on wheat (variety: BARI Gom 24) was carried out during 2013–2014 at the experimental field of IWM Division of Bangladesh Agricultural Research Institute, Gazipur. The soil was clay loam with FC 28.5 and Bulk Density 1.36 g/cc. Wheat seeds were sown on 20 December, 2013 at a spacing of 20 cm between rows at a rate of 120 kg/ha. The unit plot size was 2m ´ 1.8 m. 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 except urea were applied during final land preparation and urea was applied in three equal splits as top dress at 20, 42 and 66 days after transplanting. 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 quantity of NaCl required obtaining a given salinity level was calculated using the equation suggested by USDA, 1954. In a completely randomized block design, with three replicates, five salinity levels were compared with a fresh water control. The crop received four irrigation each at 20, 40, 60 and 80 DAS. The plots were irrigated with the restitution of 100 % of the water necessary to replenish to 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 saline water (4 dS/m)
T3= Irrigation with saline water (7 dS/m)
T4= Irrigation with saline water (10 dS/m)
T5= Irrigation with saline water (13 dS/m)
T6=Irrigation with saline water 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 above-ground biomass were determined at successive phonological stages. Ten plants were cut at ground level and chosen as samples. Then the plant samples were divided into leaves and stems. Leaf area of each plot samples were 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 7 April 2014 at hard maturity and manually threshed with 100% grain recovery. Number of spike 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 grain dry weight and shoot dry 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.