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المستخلص: Two agricultural experiments were conducted to study the role of silicon in reducing the effect of salinity of irrigation water and toxicity of some heavy metals (Cd,Mn, and Pb) and growth of maize plant ( Zea mays L. ). The first experiment was consists five levels of silicon ( 0 , 75 , 150 , 225 and 300 mg Si Kg - 1 soil ) as the form of potassium silicate ( K2SiO3 ) which was added with irrigation water prepared previously in four saline levels with electrical conductivity ( 2 , 4 , 6 and 8 dSm - 1 ) to field capacity level. These four levels of saline water were added to two different soils , Abu - Al khasib soil (silty clay loam) and Al - Zubeir soil ( loamy sand) soil .The experiment was conducted in plastic pots by using factorial experiment with three factors 2 × 5 × 4 (soils × silicon levels × irrigation water salinity levels ) with three replicates to be 120 units for all experiment . After two months of planting, the shoot and root of plant were collected and dry weight of each them was recorded. Silicon , nitrogen , phosphorus , potassium , calcium , magnesium and sodium concentration were measured, at the same the time uptake of these elements and potassium to sodium ratio were measured . leaf area , electrolyte leakage , and electrical conductivity ( EC ) of soil were measured after planting.In general and in most of them, the results pointed out that there was an increasing in all studied parameters with the increasing of silicon levels with statistical differences especially in the level 300 mg Si Kg - 1 soil where the percentage of this treatment was superior in contrast with control where was more than 209% of dry weight of shoot and nearly 200% of dry weight of root.The results indicated that Abul - Kaseeb soil was surpassed with most studied parameters significantly. There was a significant effects of salinity water in decreasing all plant parameters, while the bi and tri interactions treatments didn't reach significant effect for shoots and roots accept cadmium and magnesium concentration .Four levels of silicon ( 0 , 75 , 150 and 300 mg Si Kg - 1 soil ) with three heavy metals ( Cd , Mn and Pb ). Cadmium ( 0 , 5 , 10 , 15 mg Cd Kg - 1 soil ) , manganese ( 0 , 200 , 400 , 800 mg Mn Kg - 1 soil ) lead ( 0 , 200 , 400 , 600 mg Pb Kg - 1 soil ), in second agricultural experiment were used in pot experiment for Abu - Al khasib soil with complete randomized design of factorial experiment with two factors ( 4 × 4 ) ( silicon level × element level ) with three replicates to confirm 48 units for each element . After 60 days of planting , the plants wereharvested and collected for both shoot and root , dry weight of each of them were recorded . ( Si , Cd , Mn and Pb ) contention in shoot and root were measured. The results appeared that there was superior of dry weight, Si contention of root and shoot due to Si addition in contrast with the control in all studied treatments of heavy metals specially level 300 mg Si Kg - 1 soil . As well , addition heavy metals in its most lead to decreasing weight of shoot and root with statistical differences whereas this addition of heavy metals leads to increasing of plant concentration from them with significant levels. As regards twofold interaction effect , of addition Si with heavy metals on growth parameters was no statistical differences of most of treatments except interaction effect of ( Cd contention ) in Cd treatment , dry weight of Mn experiment , Si contention , Pb concentration in Pb experiment for both of shoot and root were significant differences .