The Effect of Irrigation Water Quality and Quantity on Soybean Yield in Golestan Province

One of the consistency ways to endure precipitation scarcity beside coastal region of country is using unconventional waters such as Sea water. The target of this study is to investigate the feasibility of mixingCaspian Sea water with available common water and different irrigation water levels on yield and oil content of soybean in Golestan province. An experiment in a completely randomized factorial design with 9 treatments and three replications was carried out to investigate the simultaneous effects of salinity of mixing Caspian Sea water with common water and different irrigation water levels on yield and oil content of soybean in research farm of Gorgan University of Agricultural Sciences and Natural Resources. The treatments were including three main treatment irrigation levels of 75 %, 100 % and 125 % of crop water requirement and 3 sub-treatments involved the irrigating with well water with salinity 0.6 dsm-1, 5 dsm-1 (salinity threshold tolerated by soybean) and 8 dsm-1 (Over the salinity threshold) ,With three replication was down in 27 basins with 3 × 3 meters surface. The statistical analysis showed that the effect of Caspian Sea water salinity mixed with well water on the weight of one thousand seeds, plant weight and oil content was significant at the one percent level. Also the effect of irrigation level on weight of one thousand seeds and plant weight was significant on 1 percent but on oil content percent was not significant. Although irrigation water amounts had significant effect on oil content percent at 5 percent probability. For grain yield and biomass, the performance was reduced with increasing salinity levels So that the highest yield was observed in treatment I2S1 (100% of irrigation level and no saline water) and also the lowest yield was observed In treatment I3S3 (125% of irrigation And 8 ds/m of salinity). The highest water efficiency in was observed in control treatment around 29.83 kg/hac.mm and also the lowest efficiency was observed in treatment I3S3 (125% irrigation level with 8 ds/m of salinity) around 6.06 kg/hac.mm.