Comparison of germination and characteristics of desert mustard seedlings in the growth substrates of mineral tailings and habitat soil

Iron and related mineral industries are one of the important pillars in industrial development. Extraction of iron ore and steel production is not possible without land degradation, and in this processing, in addition to steel, is a large volume of mineral tailings will be produced that, if not properly managed, will be able to pollute soil, air, and water, that can pose significant health challenges. The aim of this study is to evaluate the establishment and germination of desert mustard on Gol Gohar iron mine tailings in order to biological rehabilitate the tailings.

At first, sampling of tailings and soil of desert mustard (Sinapis arvensis L.) habitat from Gol Gohar mine area was done. In order to compare the particle dimensions, Granulation was done by dry sieving for both substrates and some of their physicochemical properties were investigated. Properties such as bulk density, EC, pH, Organic carbon, Phosphorus, Nitrogen, and Lime for tailings and soil were determined by conventional laboratory methods. Desert mustard seeds before planting in soil and tailing,  were tested for germination. After ensuring vigor and germination of seeds, they were planted in plastic pots with soil and mineral tailings and randomly placed in the growth chamber, irrigated daily with distilled water until the end of the experiment. Germination was recorded daily for 16 days until germination stopped. After this period, the planting medium of the pots was washed with a gentle stream of water and the seedlings of each treatment were weighed separately and their root and shoot lengths were measured. By counting the germinated seedlings, Germination Percentage, Mean Germination Time, Coefficient of Velocity of Germination, Germination Index, Mean Daily Germination Percent, Peak Value for Germination, T50,  Germination Value, Seedling Vigor Index were calculated based on the Common formulas, and at the final step, the mean of all data was tested by means of an independent t-test.

The results of the independent t-test showed that there was no significant difference between pH and EC in the two substrates, but the difference between Carbons, Phosphorus, Nitrogen, Lime; Specific mass, mean particle diameter, and ᵠ index between the two treatments is statistically significant (P < 0.01). The Mean Daily Germination Percent results show that the onset of seed germination was in two simultaneous treatments, but the peak of germination has occurred for the soil substrate of 16.66% on the fourth day and for the tailings substrate of 12.85% on the fifth day so in addition to the peak germination time, Germination Percentage is less in the tailing substrate. Although the Germination Percentage in the soil of the mustard habitat is equal to 64.28% and this is more than the Germination Percentage in tailings substrates, which is 56.19%, but like to Coefficient of Velocity of Germination and Mean Daily Germination Percent, The difference between the means is not statistically significant. This is while Mean Germination Time, Seedling Vigour Index, and T50 showed a significant difference (P < 0.05), in other hands the difference between the mean of the other parameters included Germination Value, Peak Value for Germination, Germination Index, Seedling weight, and Root to stem ratio, also is significant (P < 0.01).

The results showed that the lack of N, C, and P in mineral tailings have a negative and inhibitory effect on the growth of mustard seedlings. Strengthening the tailings with nutrients is a vital treatment for the establishment and growth of plant seedlings, meanwhile adding Lime to tailings is essential to reduce the negative effects of heavy metals on plants and soil. On the other hand, it should be borne in mind that ecological remediation of mineral tailings will not be available in the short term without the use of unpolluted and biologically active soil, so topsoil and overburden can be used as an important and reliable source of seeds for regenerate vegetation.