Effect of Phosphate fertilizer in salinity stress conditions on Cadmium fate in the plant and qualitative characteristics of tobacco

The use of phosphate fertilizers in tobacco cultivation is an important step in increasing yield. Since Triple Super Phosphate (TSP) fertilizer has a low amount of cadmium(Cd), phosphorus of fertilizer and salinity of irrigation and soil have interaction effect on the mobility and absorption of this element, therefore the exact determination of the absorbed Cd by the tobacco plant is crucial due to the use of TSP Fertilizer and different irrigation salinity stresses on the fate of absorbed Cd by tobacco and its smoke. Tobacco resistance to the salinity of sodium chloride was under 50 mM, and the salinity of 50 mM and more, reduced the photosynthesis and yield of the tobacco plant.

This study was carried out to investigate the interaction of three factors of TSP, irrigation water salinity, and soil Cd contamination on the Cd in the plant and qualitative characteristics of tobacco in Bardaskan city, 2016 and in the greenhouse condition. Irrigation salinity was at 3 levels of 0, 20 and 40 mM of NaCl, TSP was at two levels of 0 and 1.5 g.kg-1 and soil Cd contamination were at two levels of 0 and 12 mg. kg-1 soil in a factorial arrangement in a completely randomized design experiment. Data were analyzed by SAS statistical software and Tukey test was used to compare the means.

The results of this study showed that the use of TSP in Cd-contaminated soils at 0, 20 and 40 mM salinity levels, increased shoot Cd concentration of the tobacco plant by 3.43, 4.94 and 33.3, 4 times of root Cd concentration and by increasing the salinity, the concentration of Cd in both root and aerial parts of the plant increased. With the increase in salinity from zero to 20 mM, the concentration of Cd in the smoke of cultivated tobacco in contaminated soil with Cd increased by 65% compared to zero salinity. Increasing salinity from zero to 40 mM, increasing the concentration of Cd in smoke Tobacco reached 83.2%. The application of TSP at all salinity levels showed an increase in the dry matter and root growth, concentration and amount of root and shoot Cd.

In 40 mM irrigation water, TSP caused the highest shoot Cd concentration in tobacco plant compared to the control, and the combined effects of both salinity and TSP factors were more than each of them separately. In all three levels of irrigation salinity, RF, TF and EF increased in the presence of TSP. The highest RF amount was observed with 1.71% in Cd-contaminated soil without TSP and in salinity of 20 mM irrigation water. As the salinity levels increased, EF increased, but the RF increased to 20 mM, and then the decrease was observed. With increasing salinity of irrigation water from 0 to 20 mM NaCl, Cd content of plants grown in Cd-contaminated soils increased by 33.7%, but this increase for 40 mM was 26.31%. With increasing sodium chloride irrigation up to 20 mM, Cd content of the tobacco plant increased. The application of TSP in high salinity of irrigated water and Cd-contaminated soils caused more Cd absorption by tobacco plants, so in which soil and water conditions, fertilization should be restricted.