Abstract:

【Objective】 The aim of this study was to find the most reasonable improvement measures for iron tailings to improve its suitability for growing Pinus tabulaeformis and Pinus sylvestris var. mongolica, in order to provide a theoretical basis for soil improvement and vegetation restoration for iron tailing. 【Method】 Application of inorganic fertilizer, organic fertilizer (pig manure) and addition of soil were taken as measures for improving substrate of the iron tailing, pot experiment with treatments of application of different proportions of inorganic fertilizer and organic fertilizer, and addition of soil to the iron tailings was established to study the influences of different improvement methods on physicochemical properties of the iron tailings and the growth of seedlings of P. tabulaeformis and P. sylvestris var. mongolica. 【Result】 With increase of the proportion of inorganic fertilizer, the soil density, field water-holding capacity, capillary water-holding capacity, saturation water-holding capacity and total porosity were not significantly different from those of 100% tailing used as the control.With increase of the proportion of organic fertilizer, the field water-holding capacity,capillary water-holding capacity, saturation water-holding capacity and total porosity showed a trend of obvious increase, soil density showed a trend of decrease, but significant difference (P< 0.05) was found between the treatment of application of 10% proportion of pig manure and the treatment of 100% tailing. With the increase of soil proportion, the soil density was decreased gradually, while the field water-holding capacity, capillary water-holding capacity and saturation water-holding capacity increased gradually. All the parameters (except the field water-holding capacity) reached the significant level (P< 0.05) of difference between the treatments and the 100% tailing when the proportion of soil addition reached 75%. All of the electrical conductivity, soil cation exchange capacity and the contents of total nitrogen, total phosphorus, total potassium, available nitrogen, available phosphorus and available potassium increased significantly with the increase of the proportion of application of fertilizers and soil. The application of 10% pig manure had the largest content of total nitrogen and total phosphorus, 6.38 and 3.33 times respectively of those of the 100% tailing, and the contents of available nitrogen, available phosphorus and available potassium were 5.78, 12.5, and 4.32 times respectively of those of the 100% tailing.The content of total phosphorus decreased as the increase of the proportion of soil addition, and the total potassium content in the treatment of soil addition was significantly higher than that in the tailing.The content of available nutrients became obviously improved when the proportion of soil addition reached 25%, reaching the maximum values (78.41, 44.43, and 58.67 mg·kg^-1).There was no significant difference in the contents of available nutrients between the treatment of application of 5% proportion of organic fertilizer together with inorganic fertilizers of 1.76 g NH₄NO₃and 0.88 g KH₂PO₄and the treatment of application of 5% proportion of pig manure. Similarly, the contents of available nutrients of the treatment of 25% proportion of soil addition together with application of inorganic fertilizers of 1.76 g NH₄NO₃and 0.88 g KH₂PO₄were not significantly different from the treatment of only 25% proportion of soil addition. The growth of P. tabulaeformis and P. sylvestris var. mongolica was promoted by the addition of soil and application of inorganic fertilizers, however application of organic fertilizer could inhibit the growth. Under the same condition, the growth and the survival rate of P. tabulaeformis were better than that of P. sylvestris var. mongolica 【Conclusion】 In summary, application of organic fertilizer can significantly improve the physical properties, contents of total nutrients and available nutrients of the iron tailings, and addition of soil had significant influence on contents of alkali hydrolyzable nitrogen and available potassium, but application of organic and inorganic fertilizers together, and addition of soil and applications of inorganic fertilizer together did not significantly improve the content of available nutrients. There were different effects of different treatments on the growth of P. tabulaeformis and P. sylvestris var. mongolica, addition of soil and application of inorganic fertilizers could promote the growth, but application of organic fertilizers could inhibit the growth; under the same condition, P. tabulaeformis was better than P. sylvestris var. mongolica in growth, more suitable for restoration of wasteland of iron tailings.

Key words: iron tailings, improvement measures, physical and chemical properties of substrate, vegetation restoration