| In order to solve the problem of difficulty of afforest on iron tailings due to the drought, barrens, poor ability of soil and water conservation of iron tailings, the experimental plots were designed in the mining area belongs to Tangshan Shougang Ma Lan iron ore Co. Ltd. Medicago sativa, Amorpha fruticosa, Orychophragmus violaceus and Viola philippica were planted in the experimental plots. In the design of the experimental area, 2 factors 4 levels combination design was used with a total of 16 treatements, and repeat 3 times. Super absorbent polymers treatment(L/m2) was 0(B0), 2.88(B1), 14.4(B2), 28.8(B3), a total of 4 levels; organic fertilizer treatment(kg/mu) was 0(N0), 1500(N1), 7500(N2), 15000(N3), a total of 4 levels.Through the observation of the growth of the plant, the effect of different improvement methods on the physical and chemical properties of tailings matrix had been analyzed, to determine the best choice for tailings matrix improvement and dominant species for iron tailings wasteland restoration and provide theoretical basis for iron tailings matrix improvement and vegetation restoration.The main results were as follows:(1) The effect of different improvement measures on the physical properties of tailings matrixDifferent improvement measures had markedly effects on the matrix structure and water conservation ability of soil in 0-20 cm tailings surface, but no significant effects were found on improvement of the physical properties of 20-60 cm deep soil. Organic fertilizer mixed with water retention agent could improve the structure of the tailings soil matrix, better than the single application of organic fertilizer or water retention agent.At the same level of the water retention agent, soil density decreased with the increasing of organic fertilizer level. Organic fertilizer could decrease the density of soil in 0-10 cm, 10-20 cm deepth by 0.63-7.59% and 0.63-6.88% respectively. At the same level of the organic fertilizer, soil density slightly increased with the increasing application of super absorbent polymers. The treatment of B3-N3 had the best effect on the improvement of the soil water content and water holding capacity, which could make the 0-10 cm, 10-20 cm soil layer bare tailings(CK) in natural water content increased 45.06%, at the same time, the soil field capacity, capillary water holding capacity and capillary moisture capacity were respectively increased 8.78%, 9.58% and 9.53%. The treatment of B1-N3 and B2-N3 did not show significant differences with B3-N3 in the indicators mentioned above.(2) The influence of different improvement measures for chemical properties of tailings matrixApplying organic fertilizer and water retention agent could more effectively improve tailings substrate surface(0-20 cm) chemistry, organic fertilizer and water retention agent mixed with a single organic fertilizer or single water retention agent, more beneficial to increase the fertility of tailings. At the same level of the water retention agent, increasing organic fertilizer application could make the 0-10 cm, 10-20 cm soil layer of tailings matrix p H reduced by 0.93-8.31% and 0.92-5.16% respectively. Whether single application of organic fertilizer or cooperating with water retention agent, the organic matter, total nitrogen, alkali solution nitrogen, total phosphorus, available phosphorus, total potassium, available potassium content of tailings matrix in the 0-10 cm and 10-20 cm soil layer of were significantly improved, and the effect of applying organic fertilizer at N3 level was outstanding, and the treatment of B3-N3 achieved maximum.(3) The influence of different improvement measures on Medicago sativa growthThe annual growth in plant height of Medicago sativa of treatment B1-N3 was the best and increased 83.07% compared with Medicago sativa grown in bare tailings. The annual ground diameter of Medicago sativa maximized in treatment of B2-N3, and increased 100% compared with a bare tailings(CK). At organic fertilizer N3 level, The root length, the ground biomass, and underground biomass of Medicago sativa were large. In the same time, there was no significant difference between the three treatments, and the effect of treatment B3-N3 was the best, average root length was 43.67 cm, which was 1.82 times long of Medicago sativa in the bare tailings(CK). The ground biomass was 1334.89 g/m2, which was 49.07 times of Medicago sativa in bare tailings. Underground biomass was 427.99 g/m2, which was 16.63 times of Medicago sativa in the bare tailings(CK).(4) The influence of different improvement measures on Amorpha fruticosa growthSingle application of organic fertilizer was more important than single water retention agent in various growth indices. The effect of organic fertilizer mixed with water retention agent was superior to applying single organic fertilizer or water retention agent. Plant height and coverage of the annual growth was best in the treatment of B1-N3 and plant growth increased by 77.15% compared with bare tailings. Coverage of the annual growth was 39.88 times that of the bare tailings; Annual ground diameter of Amorpha fruticosa in treatment B3-N3 was best, which was 3.40 times that of bare tailings(CK). The root length, ground biomass and underground biomass of Amorpha fruticosa at organic fertilizer N3 level(B1-N3, B2-N3, B3-N3) was outstanding, which was no significant difference between three treatments, and the treatment of B3-N3 was the best, average root length was 41.67 cm, which was 3.16 times that of in bare tailings; The ground biomass was 147.29 g/m2, which was 4.08 times that in bare tailings; Underground biomass was 118.70 g/m2, which was 4.86 times that in bare tailings.(5) The influence of different improvement measures on Orychophragmus violaceus growthDifferent improved processing, the whole Orychophragmus violaceus looked like poorer. In the bare tailings(CK), treatment B0-N1 and B1-N0, all Orychophragmus violaceus died. In the other treatments, ground diameter growth had no significant difference, between 9.25-14.22 cm, 0.94-1.34 cm respectively. In treatment of B2-N3, B3-N3 and B3-N2, the plant height of Orychophragmus violaceus was 20.00 cm, 18.67 cm and 18.67 cm respectively. In the treatment B2-N2, B1-N3, aboveground biomass of Orychophragmus violaceus respectively was 13.56 g/m2, 13.37 g/m2. In the treatments of B1-N3, B2-N2, underground biomass of Orychophragmus violaceus was 9.77 g/m2, 8.25 g/m2 respectively.Taken together, the treatment B3-N3 was recommended as the best choice for tailings matrix improvement and Medicago sativa was recommended as dominant species for Iron tailing wasteland restoration. |
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