[Effects of combined application of water retention agent and organic fertilizer on physico-chemical properties of iron tailings.]

In order to analyze the effects of combined application of water retention agent and orga-nic fertilizer on physico-chemical properties of iron tailings and to find the optimal proportion of water retention agent and organic fertilizer for the improvement of iron tailings, the experimental plots of the combination trials with 2 factors in 4 levels were designed in the iron tailings of Qian'an Shougang through investigating some indexes of physico-chemical properties such as bulk density, moisture capacity, porosity, pH and the contents of organic matter, nitrogen, phosphorus and potas-sium. The biomasses of Medicago sativa and Amorpha fruticosa planted in the experimental plots were measured to verify the improvement effects. 4 levels of super absorbent polymers (L·m-3) used in treatments were 0 (B0), 10 (B1), 50 (B2), 100 (B3), and 4 levels of organic fertilizer (kg·m-2) were 0(N0), 2.25 (N1), 11.24 (N2), 22.49 (N3). The improving effects of different treatments on physico-chemical properties of iron tailings were mainly reflected in the surface layer of 0-20 cm. All the tested indexes were significantly different from control (CK) in the layer of 0-20 cm. The improvement effects of organic fertilizer on physical and chemical properties of iron tai-lings were better than that of water retention agent. In the 0-20 cm layer, the bulk density, non-capillary porosity, organic matter, rapidly available phosphorus, and available potassium under all treatments of adding water retention agent individually were not significantly different from the CK, while significant difference was observed when the organic fertilizer was solely applied in B0N2 and B0N3 treatments. The improvement synergy effect of organic fertilizer and water retention agent was better than that of organic fertilizer or water retention agent, respectively. In 0-20 cm layer, all the indexes obtained from treatment B3N3 performed best and were significantly different from the CK, which was the optimum for the improvement of iron tailings.